Dissertations / Theses on the topic 'Highly nonlinear fibre'
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Camerlingo, Angela. "New optical fibre based technologies and their application in highly nonlinear systems." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/183175/.
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This thesis investigates new fibre technologies and their application in nonlinear optical systems, designed mainly for telecommunications. The thesis includes a study of two different directions in achieving a high nonlinearity in a fibre system, namely holey fibres filled with nonlinear liquids and soft glass, small core microstructured fibres. The challenges arising from the development of liquid-filled structures have made soft glass microstructured fibres the technology of choice for the realisation of highly nonlinear systems Amongst the various soft glasses, commercially available lead-silicate glasses are identified as the material for the development of highly nonlinear fibres. Small-core, leadsilicate fibres with different designs are considered within this thesis. A solid core holey fibre design as well as two all-solid designs, a multi-ring cladding and a simpler W-index profile, are characterised. The measurements confirm the advantages of the all-solid designs over the holey structures and reveal the possibility to achieve simultaneously a high nonlinear coefficient and a novel dispersion profile in such fibres. Some of the presented fibres are employed in all-optical wavelength conversion schemes based on fourwave-mixing. Numerical simulations and experimental results are combined to study the performance of the fibres and demonstrate their use in wavelength conversion devices. In particular, a lead-silicate W-index profile fibre, showing a high nonlinear coefficient of 820W−1km−1 with a near zero dispersion profile at telecoms wavelengths, is employed to demonstrate a flat conversion gain in the whole C-band. The same fibre is then employed in FWM-based systems to demonstrate multi-channel wavelength conversion, generation of high repetition rate pulses and all-optical demultiplexing. The experiments presented in this thesis clearly reveal the potential of small-core soft-glass fibres for nonlinear applications. The use of soft glass microstructured fibres in the mid-IR is also investigated. Tellurite holey fibres with different core sizes and hole arrangements are employed in a supercontinuum generation scheme.
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Zambo, Abou'ou Marcelle Nina. "Instabilité modulationnelle et concept de réservoir de photons dans les fibres optiques à très forte non linéarité." Thesis, Dijon, 2011. http://www.theses.fr/2011DIJOS045/document.
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Cette thèse présente des travaux portant sur l'instabilité modulationnelle (IM) dans des fibres optiques dotées à la fois d'une forte non linéarité et d'un fort coefficient d'absorption. Une analyse comparative des performances de plusieurs grandes classes de fibres (de verres silice et non silice) sur leur aptitude à générer des bandes latérales d'IM avec un minimum de puissance de pompe, et sur la plus courte distance possible, est effectuée. Les fibres de verres non silice de type Chalcogénure ou Tellure apparaissent à première vue comme étant les plus performantes, mais un examen attentif révèle que leurs spectres sont altérés par un phénomène de dérive en fréquence des bandes latérales d'IM, qui est provoquée par une forte absorption du laser de pompe. Nous développons alors une méthode qui permet de supprimer la dérive en fréquence des bandes latérales d'IM dans les fibres à fort coefficient d'absorption. Cette méthode, que nous avons baptisé "méthode du réservoir de photons", consiste à créer au sein de la fibre, par un ajustement approprié des paramètres de dispersion d'ordre deux et quatre, un réservoir de photons qui alimente in situ le processus d'IM en lui fournissant continuellement l'équivalent de la quantité de photons détruits par l'absorption matérielle au cours de la propagation. L'efficacité de la méthode du réservoir de photons est démontrée sur des processus d'IM aussi bien en configuration scalaire que vectorielle. Cette démonstration marque un progrès décisif vers des dispositifs de génération de fréquences optiques qui seront extrêmement précis et stablesThis thesis considers modulational instability (MI) in optical fibers that have both a strong non-linearity and strong absorption coefficient. We carry out a comparative analysis of the performance of several major classes of silica- and non-silica glass fibers, on their ability to generate MI sidebands with a minimum of pump power, and over the shortest distance possible. Chalcogenide glass fibers appear at first sight as being the most competitive, but a careful examination reveals that their spectra are altered by a phenomenon of frequency drift of the MI sidebands, caused by a strong depletion of the pump. We have then developed a method which allows to suppress frequency drifts in MI processes in fibers having strong absorption parameters. The fundamental idea of this method, that we called "the photon reservoir method", is to create in the fiber, by an appropriate adjustment of the second-order and fourthorder dispersion coefficients, a photon reservoir which supplies (in situ) the MI process by continually providing the equivalent of the amount of photons destroyed by absorption during the propagation. We have demonstrated the effectiveness of the method of photon reservoir on MI processes, in scalarand vector configurations, using glass fibers endowed with extremely high nonlinear parameters. This method constitutes a decisive step forward in the development of highly competitive devices for optical frequency generation
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Ortigosa, Blanch Arturo. "Highly birefringent photonic crystal fibres : linear and nonlinear effects." Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760818.
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Yusoff, Zulfadzli. "Applications of highly nonlinear holey fibres in optical communications." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/15465/.
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Holey fibre (HF) is a new type of fibre that uses rings of air holes around a solid core toconfine light. A small core HF with a high air fill fraction can have effective nonlinearitycoefficient of around 10-100 times greater than conventional fibre. Apart from that, its dispersion value is also highly tailorable simply by changing the structural dimensions. These two characteristics make HFs attractive as a nonlinear medium. This thesis reports the first demonstration of various nonlinear fibre devices based on HFs. Thediscrete Raman amplifier is an attractive option to extend optical transmission systems into the optical communication bands outside the conventional erbium doped fibre amplifier (EDFA). We demonstrated a high gain discrete Raman L-band amplifier using a relatively short highly nonlinear HF. We also demonstrated a high extinction ratio, SRS based, intensity modulator using the same HF. Stimulated Brillouin scattering (SBS) is the most dominant nonlinear effect in optical fibres for a narrow linewidth system. SBS based devices could have an extremely low threshold value if highly nonlinear HF were to be used. We demonstrated a HF based Brillouin laser with a high experimentally observed threshold value. This is found to be mainly due to reduction in the effective gain coefficient caused by structural non-uniformity along the HF length. This has motivated us to study the relation between HF structural parameters and the Brillouin characteristics. This was done using two techniques: Brillouin optical time domain reflectometry (BOTDR) and the pump probe technique. A spectrally sliced pulse source is a cost effective solution to a multiwavelength transmitter. We demonstrated a HF based spectrally sliced pulse source. This was done by utilizing self phase modulation (SPM) to generate a supercontinuum in a normally dispersive HF before slicing the spectrum using an arrayed waveguide grating. Wavelength conversion is an important enabling technology for complex future optical networks. We showed in two separate experiments that by using a short length highly nonlinear HF, efficient wavelength conversion based on XPM as well as FWM can be achieved. A nonlinear thresholding device can improve the contrast of a pattern-recognition signature in an OCDMA system. Using a short highly nonlinear HF, we demonstrated a nonlinear thresholder for use in a super-structured fibre Bragg grating (SSFBG) based OCDMA receiver.
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Fung, Wai-lam. "A novel all-optical wavelength exchange in highly nonlinear fiber." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39558782.
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馮慧琳 and Wai-lam Fung. "A novel all-optical wavelength exchange in highly nonlinear fiber." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558782.
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Ettabib, Mohamed A. "All-optical signal processing in novel highly nonlinear fibres and waveguides." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/368583/.
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All-optical signal processing has recently become an attractive research field, a result of nonlinear optical systems making major advances in terms of cost, compactness, energy consumption, integrability and reliability. This technology has impacted several areas ranging from telecommunications and biomolecular sensing to military and quantum communications, and spanning a vast range of frequencies from the near to mid-infrared. This PhD research project was aimed at investigating the features and feasibility of two state-of-the-art all-optical signal processing technologies: highly nonlinear soft glass fibres and silicon-based waveguides. Of the various soft glasses available, lead silicate and tellurite are considered within this thesis. The optical properties of a highly nonlinear lead silicate W-type fibre are studied and the design process of such fibres is explained in detail. A number of telecommunications-based all-optical processing applications are also demonstrated in this fibre technology. Phase sensitive amplification is demonstrated in the W-type fibre and the process is used to regenerate the phase of 40 Gbit/s differential phase shift keying (DPSK) signals. The optical characteristics of a highly nonlinear tellurite fibre are also studied both at 1.55 and 2 µm. Efficient four wave mixing (FMW)-based wavelength conversion of 1.55 µm signals is demonstrated in the fibre and a detailed numerical study into the potential of the fibre in realizing phase-matched mid-infrared (MIR) to near-infrared (NIR) spectral translation is conducted. The second all-optical signal processing platform investigated in this project is silicon germanium (SiGe) waveguides. A detailed account of the linear and nonlinear optical properties of this newly emerging silicon-based technology is reported for the first time and the potential of this platform is highlighted by demonstrating wavelength conversion of 40 Gbaud DPSK and QPSK signals. Broadband spectral translation is also demonstrated in the SiGe waveguides with record FWM bandwidths.
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Zhang, Jian. "Nonlinear methods for distributed sensing in high birefringence optical fibres." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300417.
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Malik, Rohit. "Experimental investigation of high-power continuous-wave fiber optical parametric amplifiers and oscillators." Thesis, Swansea University, 2010. https://cronfa.swan.ac.uk/Record/cronfa42491.
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Fiber optical parametric amplifiers (OPAs) are based on a highly-efficient four-wave mixing process. Their capability to give very high gain and large bandwidths have made them an attractive candidate for providing higher bandwidths for future telecommunication systems, such as wavelength-division multiplexed (WDM) photonics networks. In dynamic photonic networks a where number of channels are dropped and/or added all the time, the OPA gain for the other channels is affected. In this thesis we employed a well-known gain control technique, all-optical gain clamping (AOGC), and reduced the gain variation of fiber OPAs below 0.5 dB, under varying input conditions. We also showed an improvement in power penalties o at the bit-error rate of 10-8, from 2.5 dB to 0.5 dB for on/off keying modulation. We also investigated fiber optical parametric oscillators (OPOs). Using fiber OPAs as gain medium we realized two different continuous-wave (CW) OPOs, centred at 1561 nm and 1593 nm. One gave us watt-level output power from 1600 nm to 1670 nm, with overall tuning range of 211 nm. The output linewidth of signal and idler was measured to be 0.08 nm and 0.15 nm respectively. The OPO centred at 1593 nm gave us a record tuning range of 254 nm, and with 3 dB output coupling fraction, it gave us large output powers (20-27 dBm) from 1610 nm to 1720 nm. Using a large seed generated by a watt-level fiber OPO in the U-band, and using 3 W of CW pump source in the C-band for Raman amplification, we generated 3 W of CW output power. This gave us nearly 100% conversion efficiency. Launching a high-power CW pump with narrow linewidth into a fiber makes stimulated Brillouin scattering (SBS) a major problem. We investigated an SBS suppressor, based on a common technique of phase dithering of the pump to suppress the SBS. We compared a multitone modulation technique to modulation with a pseudo-random bit sequence (PRBS), and we showed that it can increase the SBS threshold by 4.18 dB, and is less expensive to implement.
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Kim, Jong-Kook. "Investigation of High-Nonlinearity Glass Fibers for Potential Applications in Ultrafast Nonlinear Fiber Devices." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28569.
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Nonlinear fiber devices have been attracting considerable attention in recent years, due to their inherent ultrafast response time and potential applications in optical communication systems. They usually require long fibers to generate sufficient nonlinear phase shifts, since nonlinearities of conventional silica-core silica-clad fibers are too low. These long devices, however, cause the serious problems of pulse walk-off, pulse broadening, and polarization fluctuation which are major limiting factors for response time, switching bandwidth, and maximum transmittable bit-rate. Therefore, short device length is indispensable for achieving ultrafast switching and higher bit-rate data transmission.
To shorten the required device length, fiber nonlinearities should be increased. In this dissertation, as a way of increasing fiber nonlinearities, high-nonlinearity materials of Litharge, Bismite, Tellurite, and Chalcogenide glasses have been considered. Although they have high nonlinearities, they also have high group-velocity dispersion and high losses deteriorating the performance of nonlinear fiber devices seriously. The aim of this work is to investigate how these high-nonlinearity glasses affect the performance of nonlinear fiber devices, taking into consideration both the advantages and disadvantages. To achieve it, the critical properties of various nonlinear fiber devices constructed with the different types of high-nonlinearity glasses and different types of fibers have been evaluated.
It turned out that the required device lengths of nonlinear fiber devices constructed with the high-nonlinearity glasses were significantly reduced and high group-velocity dispersions and losses could not be major problems due to the extremely short device length. As a result, it would be possible to suppress the problems of pulse walk-off, pulse broadening, and polarization fluctuation in nonlinear fiber devices by introducing high-nonlinearity glasses, thus enabling ultrafast switching and higher bit-rate data transmission.
Furthermore, in this dissertation, a new scheme of wavelength-division demultiplexing based on the optical Kerr effect has been proposed for the first time. The new scheme can turn the disadvantage of the extremely high group-velocity dispersion of high-nonlinearity glasses into an advantage of wavelength-division demultiplexing. Finally, it now would be possible to greatly increase maximum transmittable bit-rate in optical communication systems by simultaneously demultiplexing optical time-division-multiplexed signals and wavelength-division-multiplexed signals with an optical Kerr effect-based demultiplexer.Ph. D.
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Goel, Nitin Kumar. "Development of "Core-Suction" Technique for Fabrication of Highly Doped Fibers for Optical Amplification and Characterization of Optical Fibers for Raman Amplification." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29302.
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This thesis presents a novel technique named "Core Suction" for fabricating optical fiber preforms for manufacturing highly doped fibers (HDFs) for optical amplification (Raman effect based or Erbium fiber based). The technique involves drawing the molten non-conventional core glass material into the silica cladding tube to form the preform. The developed technique is simple, inexpensive and shows great potential for fabricating preforms of highly nonlinear non-conventional multi-component glasses as the core material. Preforms were made with various core glasses such as Schott SF6, Lead-Tellurium-Germanate, Lead-Tellurium-Germanate- Neodymium -Erbium and MM2 in silica cladding tubes and then pulled into fibers.
The fabricated fibers were measured for refractive index profile, loss spectrum and spontaneous Raman spectra. Elemental analysis of the fiber samples was also performed using an electron microprobe. Erbium doped fiber amplifiers (EDFAs) were setup using 30 cm, 5cm and 1 cm lengths of fabricated erbium doped fibers and their gain spectra measured. The distributed gain spectrum for an EDFA was also measured using an optical frequency domain reflectometery (OFDR) technique. Commercial dispersion compensated fiber (DCF) with very high GeO2 doping was used to setup a Raman amplifier and the gain spectrum measured.
One of the needs of Raman amplification in optical fibers is to predict an accurate Raman gain, based on the fiber's refractive index profile. A method of predicting Raman gain in GeO2 doped fibers is presented and the predicted Raman gain values are compared with the measured ones in the same fibers. Raman gain issues like the dependence of the Raman gain on the GeO2 concentration, polarization dependence were taken into account for the gain calculations. An experimental setup for Raman gain measurements was made and measurement issues addressed. Polarization dependence of the Raman gain in one kilometer of polarization maintaining fiber was also measured.Ph. D.
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Luo, Linqing. "Time-frequency localisation of distributed Brillouin Optical Time Domain Reflectometry." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274568.
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Distributed fibre optic sensing (DFOS) is essential for structural health monitoring (SHM) of strain changes induced during the lifetime of a structure. Among different DFOS systems, the Brillouin Optical Time Domain Reflectometry (BOTDR) takes the advantages of obtaining full frequency spectrum to provide strain and temperature information along the optic fibre. The key parameters of distributed fibre optic sensors, spatial and frequency resolution, are strongly linked with the time-frequency (T-F) localisation in the system in three parts: pulse, hardware design and optical fibre. T-F localization is fundamentally important for the communication system, whereas in this study the importance of the T-F localisation to the spatial and frequency resolution, repeatability and the measurement speed are introduced in BOTDR. In this dissertation, the development of DFOS is first introduced, including both traditional methods and new developed designs. The literature review shows the signal to noise ratio (SNR) of BOTDR can be improved by investigating its T-F localisation. In the hardware design, in order to improve the T-F localisation in hardware architecture, a Short-Time Fourier Transform-Brillouin Optical Time-Domain Reflectometry (STFT-BOTDR), which implements STFT over the full frequency spectrum to measure the distributed temperature and strain along the optic fibre, is applied so that the conventional frequency sweeping method can be replaced for high resolution and fast speed measurement, providing new research advances in dynamic distributed sensing. The STFT based BOTDR has better T-F localisation, which in turn provides an opportunity for off-line post signal processing that is more adaptable for fast speed measurements. The spatial and frequency resolution of dynamic BOTDR sensing is limited by the Signal to Noise Ratio (SNR) and the T-F localization of the input pulse shape. The T-F localized input pulse shape can enhance the SNR and the spatial and frequency resolution in STFT-BOTDR. In this study, simulation and experiments of T-F localized different pulses shapes are conducted to examine the limitation of the system resolution. The result indicates that a rectangular pulse should be selected to optimize the spatial resolution and a Lorentzian pulse could be chosen to optimize the frequency resolution, while a Gaussian shape pulse can be used in general applications for its balanced performance in both spatial and frequency resolution. Meanwhile, T-F localization is used for pulse T-F localisation optimisation. A set of Kaiser-Bessel functions is used to simulate different pulse shapes and to compare their parameters in terms of T-F localisation and their Brillouin scattering spectrum. A method using an iterative filtering algorithm to achieve the optimised pulse in terms of T-F localisation is introduced to converge the Effective-pulse Width (TEW) in the time-domain and Effective-pulse Linewidth (FEL) in the frequency domain to identify the fundamental limitations. The optimised pulse can be fitted with a 7th order Gaussian (super-Gaussian) shape and it offers the best experimental performance compared to a Rectangular pulse. The sensitivity of a sensor to strain or temperature variations due to distributed Brillouin scattering is closely related to the power distribution on the Brillouin scattering spectrum which is related to the property of the optic fibre. The performance of a highly nonlinear fibre that can generate a higher Brillouin scattering signal is compared to that of a standard single mode fibre. The results show that much higher SNR of the Brillouin scattering spectrum and smaller frequency uncertainties in the sensing measurement can be achieved by using a highly nonlinear fibre for comparable launched powers. With a measurement speed of 4 Hz, the frequency uncertainty can be 0.43 MHz, corresponding to 10 με in strain or 0.43°C in temperature uncertainty for the tested highly nonlinear fibre. In contrast, for a standard single mode fibre, the value would increase to about 1.02 MHz (25 με or 1.02°C), demonstrating the advantage of the tested highly nonlinear fibre for distributed strain/temperature sensing. Results show that, by using a small effective area highly nonlinear fibre, the strain or temperature resolution can be improved because it generates stronger Brillouin scattering signal with high SNR and high Q factor spectrum, both of which determine the optimal averaging time in a single measurement. In general, the STFT-BOTDR can achieve 1 m spatial resolution, 10 με frequency resolution on a 10 km fibre with measurement speed at about 2.5 kHz.
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Hori, Takashi, Norihiko Nishizawa, Hiroyuki Nagai, Makoto Yoshida, and Toshio Goto. "Electronically controlled high-speed wavelength-tunable femtosecond soliton pulse generation using acoustooptic modulator." IEEE, 2001. http://hdl.handle.net/2237/6768.
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Leigh, Matthew. "HIGH POWER PULSED FIBER LASER SOURCES AND THEIR USE IN TERAHERTZ GENERATION ." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/193797.
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In this dissertation I report the development of high power pulsed fiber laser systems. These systems utilize phosphate glass fiber for active elements, instead of the industry-standard silica fiber. Because the phosphate glass allows for much higher doping of rare-earth ions than silica fibers, much shorter phosphate fibers can be used to achieve the same gain as longer silica fibers.This single-frequency laser technology was used to develop an all-fiber actively Q-switched fiber lasers. A short cavity is used to create large spacing between longitudinal modes. Using this method, we demonstrated the first all-fiber Q-switched fiber laser in the 1 micron region.In addition to creating high peak powers with Q-switched lasers, created even higher powers using fiber amplifier systems. High power fiber lasers typically produce spectral broadening through the nonlinear effects of stimulated Raman scattering, stimulated Brullion scattering, and self-phase modulation. The thresholds for these nonlinearities scale inversely with intensity and length. Thus, we used a short phosphate fiber gain stage to reduce the length, and a large core fiber final stage to reduce intensity. In this way we were able to generate high peak power pulses while avoiding visible nonlinearities, and keeping a narrow bandwidth.The immediate goal of developing these high power fiber laser systems was to generate narrowband terahertz radiation. Two different wavelengths were combined into the final amplifier stage at orthogonal polarizations. These were collimated and directed into a GaSe crystal, which has a very high figure of merit for THz generation. The two wavelengths combined in the crystal through the process of nonlinear difference frequency generation. This produced a narrowband beam of THz pulses, at higher powers than previous narrowband THz pulses produced by eyesafe fiber lasers.
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Bordonaro, Giancarlo Giuseppe. "Nonlinear System Identification of Physical Parameters for Damage Prognosis and Localization in Structures." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/30019.
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The understanding of how structural components endure loads, in particular variable loads, is that these components gradually, over some period of time depending on the nature of the loading and the material, develop a microcrack. After some additional time and loading, the microcrack grows to a size that might be detected. Beyond that point, the microcrack propagates in a manner that can be reliably predicted by computer analysis codes. Consequently, one can define different stages for the life of a structural component. These are: 1) the period prior to the formation of a microcrack, 2) the period of microcrack growth, and finally 3) the period of crack growth. To date, structural health monitoring approaches that seek to detect cracks offer no insight into the extent of deterioration occurring in the initial stage that is a precursor to the formation of the microcrack or its growth. However, an approach that would facilitate monitoring the extent of the deterioration that takes place during this stage promises to improve life prediction capabilities of structural components.
The challenge, thus, is to develop quantitative assessment of damage accumulation from the earliest stages of the fatigue process and to provide a structure's signature that is dependent of the damage stage. One such signature is the structure's response to forced excitation. The realization of such a goal would help in advancing structural health monitoring procedures using interrogative system identification techniques and determine sensitivities of physical parameters to damage. Additionally, vibration-based spectral quantities are related to physical properties of the structure under test.
In this thesis, nonlinear response to parametric excitation is exploited for nonlinear system identification of metallic and composite beam-mass systems before damage initiation through intermediate states of damage progression to failure. Parametric identification procedure combines linear and higher order spectral analysis of vibration measurements and perturbation techniques for the derivation of the approximate solution of the system nonlinear governing differential equation. The possibility of using optical Fiber Bragg Grating sensors technology for damage localization is also assessed. Spectral moments and quantities obtained from fiber optic strain measurements are evaluated near and away from cracks to assess the relation between these moments and cracks.
Variations in parameters representing natural frequency, damping and effective nonlinearities for different levels of progressive damage in a beam-mass system have been determined. Their percentage variations have been quantified to establish their sensitivities to damage initiation. The results show that damping and effective nonlinearity parameters are more sensitive to damage conditions than the natural frequency of the first mode. Crack localization is assessed by means of optical fiber technology for a composite beam-mass system. The results show that noise levels in fiber optic signals are high in comparison to strain gage signals. Of particular interest, however, is the observation that the nonlinear response is more pronounced near the cracks than away from them.Ph. D.
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Takayanagi, Jun, Norihiko Nishizawa, Hiroyuki Nagai, Makoto Yoshida, and Toshio Goto. "Generation of high-power femtosecond pulse and octave-spanning ultrabroad supercontinuum using all-fiber system." IEEE, 2005. http://hdl.handle.net/2237/6770.
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Parsa, Shahrzad. "High-power fiber-laser-pumped picosecond nonlinear optical sources from the near- to mid-infrared." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/620786.
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Ultrafast picosecond coherent sources in the near-to-mid-infrared (IR) spectral range are of great interest for a variety of applications such as pump-probe spectroscopy, remote sensing, photobiology and novel upconversion imaging techniques. Nonlinear optics, and in particular nonlinear frequency conversion techniques, offer an efficient and effective approach towards the realization of sources emitting such radiation, as nowadays, nonlinear frequency conversion technologies are recognised to be viable and reliable sources of laser radiation with broad wavelength tunability and power scalability, without the need of cryogenic cooling.
In this thesis, we have demonstrated high-power, high-repetition-rate picosecond sources based on nonlinear frequency conversion processes through optical parametric oscillators (OPOs) and difference-frequency-generation (DFG), in order to cover the near- to mid-IR wavelength region.
We have developed a stable, high-repetition-rate picosecond rapidly tunable OPO based on fan-out designed grating periods in PPKTP nonlinear crystal. The OPO is synchronously pumped by a mode-locked frequency-doubled Yb-fiber laser in the green at 532 nm, and can provide stable and high-power radiation which is rapidly tunable from 749-962 nm in the signal and from 1189-1838 nm in the idler, at room temperature.
Further, we have demonstrated what we believe to be the first tunable high-repetition-rate picosecond source based on OP-GaP crystal in the mid-IR. Using a single-pass DFG between a mode-locked Yb-fiber laser at 1064 nm and the tunable output from a picosecond MgO:sPPLT OPO synchronously pumped by the same laser, the source generated continuous tunable radiation across 3040-3132 nm in the mid-IR at the repetition rate of ~80 MHz, in good beam quality.
Additionally, we have also presented the first high-power, high-beam-quality, idler-resonant picosecond OPO based on a multi-grating MgO:PPLN crystal tunable across 2100-4000 nm in the mid-IR. The OPO provided as much as 3.5 W of mid-IR radiation with M2 values to be better than 1.8 in both horizontal and vertical directionsLas fuentes coherentes de picosegundos ultrarrápidos en el rango espectral de infrarrojo cercano a infrarrojo medio (IR) son de gran interés para una amplia variedad de aplicaciones tales como pump-probe espectroscopia, la teledetección, la fotobiología y las nuevas técnicas de upconversion imaging. La óptica no lineal, y en particular las técnicas de conversión de frecuencia no lineal, ofrecen un enfoque eficiente y eficaz para la realización de fuentes que emiten tales radiaciones, ya que hoy en día, las fuentes basadas en la conversión de frecuencia no lineal son fuentes viables y fiables de emisión de radiaciones láser con amplia sintonía de longitud de onda y escalabilidad de potencia, sin necesidad de refrigeración criogénica. En esta tesis, hemos demostrado fuentes de picosegundos de alta potencia y alta tasa de repetición basadas en procesos de conversión de frecuencia no lineales a través de osciladores ópticos paramétricos (OPO) y generación de frecuencias de diferencia (DFG) para cubrir la región de longitud de onda de IR cercano a IR medio del espectro electromagnético. Hemos desarrollado una fuente de picosegundos estable, de alta tasa de repetición, rápidamente sintonizable, basado en un cristal PPKTP con períodos de rejilla diseñados en forma de abanico. El OPO, es bombeado sincrónicamente por un mode-locked láser de fibra de Yb, doblado en frecuencia para generar verde a 532 nm, que proporciona radiación estable y de alta potencia rápidamente sintonizable de 749-962 nm en el signal y de 1189-1838 nm en el idler, a temperatura ambiente. Además, hemos demostrado lo que creemos que es la primera fuente de picosegundos sintonizable con alta tasa de repetición basada en el cristal OP-GaP en el IR medio. Usando una DFG de un solo paso entre un mode-locked láser de fibra de Yb a 1064 nm y la salida ajustable de un OPO de picosegundo basado en un cristal de MgO:sPPLT bombeado sincrónicamente por el mismo láser, la fuente generó radiación sintonizable de 3040-3132 nm en el medio-IR a la velocidad de repetición de ~80 MHz, con buena calidad de haz. Además, también presentamos el primer OPO de picosegundos de alta potencia y buena calidad de haz, con resonancia del idler, basado en un cristal MgO:PPLN de rejilla múltiple sintonizable a lo largo de 2100-4000 nm en el IR medio. El OPO proporcionó hasta 3.5 W de radiación de IR medio con valores de M2 mejores que 1.8 tanto en dirección horizontal como vertical
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Ben, braham Fatma. "Contribution à l’étude théorique et expérimentale d’un oscillateur laser fonctionnant en régime impulsionnel dans les bandes spectrales C et L." Thesis, Angers, 2018. http://www.theses.fr/2018ANGE0025.
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Ce travail de thèse concerne le développement d’un laser à fibre générant des impulsions rectangulaires très énergétiques et accordables à l’échelle du temps et des impulsions géantes à haute énergie. En premier temps,nous avons développé un modèle numérique pour étudier la génération des impulsions rectangulaires dans un laser à fibre en forme de huit à double amplificateur.L’objectif est de montrer l’impact de l’effet non linéaire induit par la fibre micro structurée sur le contrôle de la durée d’impulsion rectangulaire générée par le laser. Un ensemble de paramètres laser nous a permis ainsi de générer des impulsions rectangulaires à haute énergie dans le régime de la résonance du soliton dissipatif (DSR). En plus, plusieurs expériences ont été mises en place pour optimiser la génération de l’impulsion DSR en termes d’énergie et de durée.Toujours sur le plan expérimental, des impulsions géantes à haute énergie à partir du laser à fibre verrouillé en phase couplé à un retard optique ont été obtenues. Cela nous a permis de générer une large plage de durée d’impulsion à l'échelle de μs à taux de répétition faible dans des cavités utilisant des absorbants saturables artificielsThis work deals with the development of a fiber laser generating high energy and width tunable square pulses and high-energy giant pulses. First, we have developed a numerical model to study the generation of rectangular pulses in a double amplifier fiber laser. The objective is to study the impact of the non-linear effect induced by the microstructured optical fiber on the control of the square pulse duration. A set of laser parameters allowed us to generate high energy square pulses in the dissipative soliton resonance (DSR) regime. In addition, several experiments have been set up to optimize the generation of the DSR pulse in terms of energy and duration. Experimentally, high energy giant pulses from a passively mode-locked fiber ring laser coupled to a long external cavity are obtained. This allowed us to generate a wide range of pulse duration of μs at a low repetition rate in cavities using artificial saturable absorbers
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Chaitanya, Kumar Suddapalli. "High-power, fiber-laser-pumped optical parametric oscillators from the visible to mid-infrared." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/83528.
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High-power, continuous-wave (cw), mid-infrared (mid-IR) laser sources are of interest
for variety of applications such as trace gas detection and remote sensing, which
require broad spectral coverage to address the most prominent absorption features
of a wide range of molecular species particularly in the mid-IR fingerprint region. On
the other hand, surgical applications require high energy sources with unique pulse
structure at specific wavelength in the mid-IR ranging from 6-6.5 m.
Optical parametric oscillators (OPOs) offer potential sources for all the above
applications. The output wavelengths of a singly-resonant oscillator (SRO) can be
coarsely tuned over wide ranges through the adjustment of the nonlinear crystal
temperature, phase-matching angle or, in the case of quasi-phase-matched (QPM) the first time. The high-energy CSP OPO marked the first demonstration of a
compact, high-repetition-rate OPO synchronously pumped by a master oscillator
power amplifier system at 1064 nm, generating an milli-joule pulses in the 6-6.5 m
spectral range, which is technologically important for surgical applications.
Additionally, we also demonstrated a fiber-based-green source at 532 nm, based
on single-pass second harmonic generation (SHG) in MgO:sPPLT, as an alternative
pump source for Ti:sapphire laser, pointing towards the future, compact fiber-laser
pumped Ti:sapphire lasers. Further efforts to improve the SHG efficiency led to
the development of a novel multi-crystal scheme, enabling single-pass SHG efficiency
as high as 56%. This generic technique is simple and can be implemented at any
wavelength.
materials, the QPM grating period. The combination of SRO with a tunable pump
laser allows the development of uniquely flexible and rapidly tunable class of mid-IR
sources.
In this thesis we have demonstrated several mid-IR OPOs in the cw as well as
ultrafast picosecond regime pumped by fiber-lasers making them compact and robust.
In the cw regime, we developed a high-power, Yb-fiber-laser pumped mid-IR OPO
based on MgO:PPLN spanning 1506-1945 nm in the near-IR and 2304-3615 nm
wavelength range in the mid-IR, efficiently addressing the thermal effects by implementing
the optimum signal output coupling. Novel materials such a MgO:sPPLT,
with better optical and thermal properties for cw mid-IR generation are explored.
High-power broadband, cw mid-IR generation is also demonstrated by using the
extended phase-matching properties of MgO:PPLN.
Further, we also demonstrated a simple, inexpensive and novel interferometric
technique for absolute optimization of output power from a ring optical oscillator.
We deployed a picosecond Yb-fiber-laser pumped mid-IR OPO based on MgO:PPLN
in ring cavity configuration to demonstrate this proof-of-principle experiment forFuentes coherentes de luz continua y de alta potencia en el infrarrojo-medio (mid-IR) son de gran interés por su aplicación en la detección de gases, detección remota y la observación de imágenes. Estas aplicaciones requieren un ancho de banda amplio para evidenciar las características que ofrece la absorción de una gran variedad de especies moleculares, particularmente en la región “finger print” del mid-IR. Por otra parte, fuentes altamente energéticas con pulsos que posean estructuras peculiares en rangos específicos de longitud de onda en el mid-IR, entre 6-6.5 m. , prometen características únicas para nuevas aplicaciones en cirugía. Osciladores ópticos paramétricos (OPOs) constituyen fuentes de luz versátiles y apropiadas para todas las aplicaciones mencionadas anteriormente. La longitud de En el régimen ultrarápido, hemos demostrado una nueva técnica de interferometría para la optimización absoluta de la potencia de salida de un oscilador óptico con una cavidad de anillo. Como demostración de principio, implementamos, por primera vez, un OPO de picosegundos en el mid-IR basado en MgO:PPLN con una cavidad de anillo bombeado por un láser de fibra de Yb. Además, hemos desarrollado un nuevo OPO de alta energía en el mid-IR basado en el material nolineal CSP. Esto representa la primera demostración de un OPO compacto de alta repetición sincrónicamente bombeado por un láser de estado sólido a 1064 nm generando pulsos de milijulios en el rango espectral 6-6.5 m. Esta radiación es importante para aplicaciones en cirugía. Adicionalmente, hemos demostrado una fuente verde, 532 nm, basada en láseres de fibra. Esta radiación se obtiene por medio de la generación de segundo harmónico (SHG) en un paso individual en MgO:sPPLT. Esto representa una nueva alternativa de bombeo para los láseres de Ti:sapphire que los harán compactos en el futuro. Los esfuerzos para mejorar la eficiencia de segundo harmónico resultaron en el desarrollo de un novedoso esquema que utiliza múltiples cristales y permite eficiencias de SHG de paso individual del 56%. Este esquema es general y simple y puede ser implementado para cualquier longitud de onda. onda de un OPO puede ser sintonizada en regiones amplias del espectro cambiando la temperatura del cristal no-lineal, el ángulo de ajuste de fase o, al considerar materiales cuasi ajuste de fase (QPM), cambiando el periodo de red. En esta tesis, hemos demostrado una gran variedad de OPOs en el mid-IR en régimen continuo y de pulsos de picosegundo. Estos OPOs han sido bombeados por láseres de fibra permitiendo un diseño compacto y resistente. En el régimen de emisión continua, hemos implementado un OPO de alta potencia basado en MgO:PPLN bombeado por un láser de fibra. Este OPO es sintonízable en el rango 1506-1945 nm correspondiente al infrarrojo-cercano y en el rango 2304-3615 nm correspondiente al mid-IR. Esta capacidad de sintonización se logra al sobrepasar eficientemente los efectos térmicos optimizando el acoplamiento de salida. Materiales nuevos como el MgO:sPPLT, con propiedades ópticas y térmicas mejoradas para la generación de radiación continua en el mid-IR han sido estudiados. Utilizando las propiedades ajuste de la fase extendió del MgO:sPPLT, fuentes continuas de alta potencia con un gran ancho de banda en el infrarrojo-medio también han sido implementadas.
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Baselt, Tobias, Christopher Taudt, Bryan Nelsen, Andrés Fabián Lasagni, and Peter Hartmann. "All-fiber supercontinuum source with flat, high power spectral density in the range between 1.1 μm to 1.4 μm based on an Yb3+ doped nonlinear photonic crystal fiber." SPIE, 2017. https://tud.qucosa.de/id/qucosa%3A35120.
Full textAbstract:
Supercontinuum light sources provide a high power spectral density with a high spatial coherence. Coherent octavespanning supercontinuum can be generated in photonic crystal fibers (PCFs) by launching short pulses into the fiber. In the field of optical metrology, these light sources are very interesting. For most applications, only a small part of the entire spectrum can be utilized. In biological tissue scattering, absorption and fluorescence limits the usable spectral range. Therefore, an increase of the spectral power density in limited spectral regions would provide a clear advantage over spectral filtering. This study describes a method to increase the spectral power density of supercontinuum sources by amplifying the excitation wavelength inside a nonlinear photonic crystal fiber (PCF). An all-fiber-based setup enables higher output power and power stability. An ytterbium-doped photonic crystal fiber was manufactured by a nanopowder process (drawn by the fiberware GmbH, Germany) and used in a fiber amplifier setup as the nonlinear fiber medium. In order to characterize the fiber’s optimum operational characteristics, group-velocity dispersion (GVD) measurements were performed. The performance of the fiber-based setup was compared with a free space setup. Finally, the system as a whole was characterized in reference to common solid state-laser-based supercontinuum light sources. An improvement of the power density was observed in the spectral range between 1100 nm to 1400 nm.
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Rydberg, Sara. "Rare Earth elements in optical materials and design of high power ytterbium fiber laser for frequency doubling using nonlinear ppKTP crystal." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-36138.
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El, Mansouri Ibrahim. "Sources impulsionnelles picosecondes tout optique à très haut débit : applications aux télécommunications optiques." Thesis, Dijon, 2013. http://www.theses.fr/2013DIJOS064/document.
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Ce mémoire de thèse présente les travaux effectués pour la réalisation de sources optiques fibrées d’impulsions picosecondes cadencées à 40 GHz dans la bande C des télécommunications. Dans une première partie, nous présentons des études numériques et expérimentales mises en place pour la génération d’un train d’impulsions cadencé à 40 GHz par la compression non-linéaire d’un battement sinusoïdal via un processus de mélanges à quatre ondes multiples. Afin d’obtenir des impulsions stables, le battement sinusoïdal initial est obtenu par la modulation en intensité d’un signal continu grâce à un modulateur Mach-Zehnder piloté au point nul de transmission. Nous démontrons également l’amélioration de la qualité des impulsions générées par la suppression de la diffusion Brillouin stimulée grâce à la mise en place d’isolateurs optiques dans la ligne fibrée de la source. Nous présentons ensuite la génération d’impulsions ultra-courtes grâce à un compresseur non-linéaire composé de quatre étages fibrés. Le train d’impulsions obtenu est alors codé puis multiplexé jusqu’à un débit optique de 160 Gbit/s. Dans la dernière partie, nous présentons les démarches mises en place en vue d’un transfert technologique, telles que la réalisation d’un prototype de la source, la recherche d’antériorité et l’étude de marchéThis thesis presents the work carried out on the realization of fibered 40-GHz picosecond optical pulse sources in the telecommunications C-band. In the first part, we present a numerical and experimental study of the generation of 40-GHz pulse trains thanks to the nonlinear compression of an initial beat-signal by multiple Four-Wave Mixing process. Enhanced temporal stability is achieved by generating the sinusoidal beating thanks to a Mach-Zehnder modulator driven at its zero-transmission working point. In order to improve the quality of the generated pulses, we also demonstrate the suppression of stimulated Brillouin back-scattering by inserting several optical isolators into the compression line. In the next part, we present the generation of low duty-cycle pulse trains by using a nonlinear compressor line based on 4 segments of fiber. The generated pulse trains have been encoded and then multiplexed to achieve a high bit rate signal (160 Gb/s). In the last part, we present the technology transfer steps of this optical source, such as creating a prototype of the source, prior art search and market research
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Semaan, Georges. "Soliton dynamics in fiber lasers : from dissipative soliton to dissipative soliton resonance." Thesis, Angers, 2017. http://www.theses.fr/2017ANGE0029/document.
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Dans cette thèse, nous étudions expérimentalement la génération d'impulsions carrées très énergétiques et accordable à l’échelle nanosecondes et d'impulsions ultracourtes à haute puissance moyenne de sortie dans les lasers à fibre utilisant les nanomatériaux comme absorbant saturable. Tout d'abord, puisque la dynamique des impulsions est dominée par l'interaction de la non linéarité et de la dispersion chromatique cubique de la fibre avec un mécanisme de discrimination d'intensité appelé absorbant saturable, la stabilité d'une distribution harmonique en mode verrouillé est étudiée par injection externe d'une onde continue.Enfin, nous avons utilisés des absorbant saturable à base de nanomatériaux déposés sur des tapers optiques dans les lasers à fibre pour générer des impulsions ultracourtes avec une puissance de sortie moyenne élevéeIn this thesis, we investigate experimentally the generation of high energy nanosecond tunable square pulses and high output power ultrashort pulses in fiber lasers. First, since pulse dynamics are dominated by the interaction of the fiber's cubic Kerr nonlinearity and chromatic dispersion with an intensity-discriminating mechanism referred to as a saturable absorber, the stability of a harmonic mode-locked distribution is studied by external injection of a continuous wave. Finally, we implemented nanomaterial based saturable absorbers in fiber laser configuration to generate ultrashort pulses with high average output power. Different techniques of achieving such components are explicitly detailed: ultrashort pulse generation in ring cavities where graphene and topological insulators are deposited on optical tapers to form a saturable absorber
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Neumann, Niels. "Signal processing with optical delay line filters for high bit rate transmission systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-64036.
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In den letzten Jahrzehnten ist das globale Kommunikationssystem in einem immer größerem Maße ein integraler Bestandteil des täglichen Lebens geworden. Optische Kommunikationssysteme sind die technologische Basis für diese Entwicklung. Nur Fasern können die riesige benötigte Bandbreite bereitstellen. Während für die ersten optischen Übertragungssysteme die Faser als "flacher" Kanal betrachtet werden konnte, machen Wellenlängenmultiplex und steigende Übertragungsraten die Einbeziehung von immer mehr physikalischen Effekten notwendig. Bei einer Erhöhung der Kanaldatenrate auf 40 Gbit/s und mehr ist die statische Kompensation von chromatischer Dispersion nicht mehr ausreichend. Die intrinsische Toleranz der Modulationsformate gegenüber Dispersion nimmt quadratisch mit der Symbolrate ab. Daher können beispielsweise durch Umwelteinflüsse hervorgerufene Dispersionsschwankungen die Dispersionstoleranz der Modulationsformate überschreiten. Dies macht eine adaptive Dispersionskompensation notwendig, was gleichzeitig auch Dispersionsmonitoring erfordert, um den adaptiven Kompensator steuern zu können. Vorhandene Links können mit Restdispersionskompensatoren ausgestattet werden, um sie für Hochgeschwindigkeitsübertragungen zu ertüchtigen. Optische Kompensationstechniken sind unabhängig von der Kanaldatenrate. Daher wird eine Erhöhung der Datenrate problemlos unterstützt. Optische Kompensatoren können WDM-fähig gebaut werden, um mehrere Kanäle auf einmal zu entzerren. Das Buch beschäftigt sich mit optischen Delay-Line-Filtern als eine Klasse von optischen Kompensatoren. Die Filtersynthese von solchen Delay-Line-Filtern wird behandelt. Der Zusammenhang zwischen optischen Filtern und digitalen FIR-Filtern mit komplexen Koeffizienten im Zusammenhang mit kohärenter Detektion wird aufgezeigt. Iterative und analytische Methoden, die die Koeffizienten für dispersions- und dispersions-slope-kompensierende Filter produzieren, werden untersucht. Genauso wichtig wie die Kompensation von Dispersion ist die Schätzung der Dispersion eines Signals. Mit Delay-Line-Filtern können die Restseitenbänder eines Signals genutzt werden, um die Dispersion zu messen. Alternativ kann nichtlineare Detektion angewandt werden, um die Pulsverbreiterung, die hauptsächlich von der Dispersion herrührt, zu schätzen. Mit gemeinsamer Dispersionskompensation und Dispersionsmonitoring können Dispersionskompensatoren auf die Signalverzerrungen eingestellt werden. Spezielle Eigenschaften der Filter zusammen mit der analytischen Beschreibung können genutzt werden, um schnelle und zuverlässige Steueralgorithmen zur Filtereinstellung bereitzustellen. Schließlich wurden Prototypen derartiger faseroptischen Kompensatoren von chromatischer Dispersion und Dispersions-Slope hergestellt und charakterisiert. Die Einheiten und ihr Systemverhalten wird gezeigt und diskutiertOver the course of the past decades, the global communication system has become a central part of people's everyday lives. Optical communication systems are the technological basis for this development. Only fibers can provide the huge bandwidth that is required. Where the fiber could be regarded as a flat channel for the first optical transmission systems wavelength multiplexing and increasing line rates made it necessary to take more and more physical effects into account. When the line rates are increased to 40 Gbit/s and higher static chromatic dispersion compensation is not enough. The modulation format's intrinsic tolerance for dispersion decreases quadratically with the symbol rate. Thus, environmentally induced chromatic dispersion fluctuations may exceed the dispersion tolerance of the modulation formats. This makes an adaptive dispersion compensation necessary implying also the need for a monitoring scheme to steer the adaptive compensator. Legacy links that are CD-compensated by DCFs can be upgraded with residual dispersion compensators to make them ready for high speed transmission. Optical compensation is independent from the line rate. Hence, increasing the data rates is inherently supported. Optical compensators can be built WDM ready compensating multiple channels at once. The book deals with optical delay line filters as one class of optical compensators. The filter synthesis of such delay line filters is addressed. The connection between optical filters and digital FIR filters with complex coefficients that are used in conjunction with coherent detection could be shown. Iterative and analytical methods that produce the coefficients for dispersion (and also dispersion slope) compensating filters are researched. As important as the compensation of dispersion is the estimation of the dispersion of a signal. Using delay line filters, the vestigial sidebands of a signal can be used to measure the dispersion. Alternatively, nonlinear detection can be used to estimate the pulse broadening which is caused mainly by dispersion. With dispersion compensation and dispersion monitoring, dispersion compensators can be adapted to the signal's impairment. Special properties of the filter in conjunction with an analytical description can be used to provide a fast and reliable control algorithm for setting the filter to a given dispersion and centering it on a signal. Finally, prototypes of such fiber optic chromatic dispersion and dispersion slope compensation filters were manufactured and characterized. The device and system characterization of the prototypes is presented and discussed
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Munasinghe, Hashan Tilanka. "Soft glass optical fibres for telecommunications applications." Thesis, 2015. http://hdl.handle.net/2440/100712.
Full textAbstract:
As the appetite for data use across telecommunications networks is predicted to continue to grow rapidly in the coming years, there is an increasing need to address the bandwidth gap that exists between the optical links that underpin high speed networks and the electronic layer typically used for processing signals at the endpoints. Nonlinear fibre optics is a potential avenue to addressing this bandwidth bottleneck, where nonlinear optical phenomena can be exploited to perform signal processing tasks, thereby allowing the broad bandwidth of optical media to be used for signal processing as well as transmission. Indeed the development of such optical signal processing devices is crucial to moving towards the next generation of communications technology - where ultra fast telecommunication networks with speeds approaching 1 Tb/s are required. This work explored the use of the enhanced optical nonlinearity and dispersion engineering possible in soft glass microstructured fibres as a basis for developing devices for broadband telecommunications applications at 1.55 μm. Two applications were considered in this research, namely multicasting and phase sensitive amplification - both of which are signal processing applications that are important to the realisation of all optical networks. A number of soft glass materials were studied in this research, primarily those with high nonlinear refractive indices such as chalcogenides, tellurites, bismuth oxide based glasses and germanates. During the course of this work a novel lead germanate glass was also developed. This glass was shown to have a high nonlinear index and relatively high mechanical strength when compared to tellurite glasses of similar refractive indices. Dispersion tailored, soft glass fibre designs were developed for both multicasting and phase sensitive amplification. The design geometry, referred to as a ‘hexagonal wagon wheel design’, was a hybrid model combining a hexagonal array geometry for dispersion engineering with a suspended core or ‘wagon wheel’ geometry for high nonlinearity. The fibre designs were optimised for each application by using a genetic algorithm based optimisation technique to achieve high and broad gain suitable for efficient signal processing at extremely high bit rates. Each fibre design was modelled for its intended application to demonstrate, numerically, that the designs were indeed capable of performing their intended application over a broad band. The modelling work used a numerical beam propagation model and demonstrated that the designs were capable of operating at the extremely high bit rate of 640 Gb/s. Advances were made to fabrication techniques during the fabrication trials of these novel designs due to the complex nature of the designs and, in some cases, the use of novel materials. A first generation, simplified hexagonal wagon wheel fibre was fabricated in the novel germanate glass developed earlier. A number of characterisation experiments were also performed on fabricated microstructured fibres, including a measurement of the dispersion profile for a tellurite fibre (that was shown to be in good agreement with modelling results) and the measurement of the nonlinear index for a fibre fabricated with the novel germanate glass - one of the few such measurements in the literature for this family of glasses. In addition to these fabrication advances and characterisation experiments, a study of dispersive waves was performed on previously fabricated hexagonal wagon wheel fibres in collaboration with colleagues at the University of California, Merced. These experiments were used to study soliton propagation in these fibres at near infrared wavelengths. Comparison of experimental data to theoretical models is shown to have good agreement - an important validation of the modelling technique.Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 2015.
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Zhang, Hui. "Lumped fiber Raman amplifiers with highly nonlinear fiber." Thesis, 2005. http://spectrum.library.concordia.ca/8713/1/MR14289.pdf.
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Fiber Raman amplifiers (FRAs) can provide broadband and low-noise-figure amplification, and the gain can be achieved at any wavelength. It has been proved that FRA is a useful technique to extend the span lengths and capacity of fiber-optic transmission systems. In particular, lumped fiber Raman amplifiers (LRAs), based on dispersion compensating fibers, have been considered in long-haul WDM transmission systems. However, noise can limit the performance of LRAs having a gain of more than 15 dB. Noise degrades the optical signal-to-noise ratio (OSNR) resulting in receiver sensitivity penalty and thus the amplifier gain is limited to some extent for a single LRA. Highly nonlinear fiber (HNLF) is a fiber with high nonlinearity to generate Raman gain efficiently and can be used as a gain medium for lumped Raman amplifiers. In this thesis, we will investigate Raman gain and noise characteristics of LRAs using HNLFs as a gain medium. It is shown that both the signal and the amplified spontaneous emission induced multiple-path interferences are suppressed in LRAs with HNLF, thus for the same Raman gain a better noise performance can be achieved independently of co-, counter- and bi- directional pumping methods, compared to LRAs with DCF gain medium. Moreover, the effect of Rayleigh scattering coefficient on LRA's noise performance improvement is also investigated. To achieve an accurate modeling, a theoretical model, which includes effects of multiple-path interference (MPI), anti-Stokes, and Rayleigh scattering, is used, and a new Raman gain coefficient scaling method is also employed in this modeling.
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Cheng-Yu, Wang. "All-Optical XOR Operation Generation Using Nonlinear Polarization Rotation in a Single Highly Nonlinear Fiber." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0016-1303200709301426.
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Wang, Cheng-Yu, and 王振宇. "All-Optical XOR Operation Generation Using Nonlinear Polarization Rotation in a Single Highly Nonlinear Fiber." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/98092753692883379196.
Full textAbstract:
碩士國立清華大學
光電工程研究所
94
In recent days, the demand for high speed photonic communication networks was much larger little by little. A key building block in many areas of optical signal processing is just the all-optical XOR logic gate. For the fiber-based reconfigurable high-speed optical network, an all-fiber solution for the XOR gate is highly desirable with the added advantages of (i) no need for OE/EO conversion, (ii) ultrafast nonlinear response time (~2-4 fs) of Kerr effect in the fiber, and (iii) excellent fiber compatibility. These advantages make highly nonlinear fiber devices to be attracting considerable attention in the aspects of many researches. In this thesis, we try to simulate to achieve all-optical XOR logic function by using polarization rotation in a single HNLF at 10 Gb/s and 20 Gb/s. Thus, we accomplished signal-processing in all-optical domain. Besides, we also try to tune some parameters, for example, the selections of the input power and wavelength of lasers and the length and fiber loss of the highly nonlinear fiber (HNLF), to investigate the influence on the performance of the all-optical XOR logic gate. The results of this research will reveal the fact that these parameters indeed play an important role in the performance of all-optical XOR logic gate by using polarization rotation in a single HNLF. As a result, we will understand how to use these appropriate parameters of all-optical XOR logic gate in order to get the better performance of it based on the concept of using a highly nonlinear fiber. These investigations and demonstrations will be useful expectedly in the field of high speed photonic communication networks for the next generation.
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Kuo, Chih-yuan, and 郭志遠. "The studies of supercontinuum source utilizing highly-nonlinear-fiber in an erbium-doped-fiber ring cavity." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/71873472621077520625.
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碩士國立高雄師範大學
光電與通訊工程學系
102
The main argument of this thesis is that delay fiber and power density in the cavity make effect on nonlinear polarization rotation and stimulating Raman scattering in the architecture of supercontinuum source. This supercontinuum source is based on an erbium-doped fiber laser and Nonlinear Polarization Rotation intensity dependent loss. The both effects of nonlinear polarization rotation and stimulating Raman scattering could be cross analyzed by changing type and length of delay fibers. Furthermore, vary the optical power density in cavity is used to investigate the threshold of the nonlinear effects. The different length of 1-m, 10-m, and 100-m of highly nonlinear fibers in the ring cavity couldn’t make the laser reach the threshold level of nonlinear effects. Because of the fusing losses and the delaying fiber losses, the total optical power losses in the system can’t activate the HNLFs to generate the supercontinuum lasing in the fiber ring cavity.
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HAO-YU, PAN, and 潘浩宇. "The studies of supercontinuum generation in highly nonlinear fiber using tunable bandwidth seed signal." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/55419399386277498469.
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碩士國立高雄師範大學
光電與通訊工程學系
102
We produce supercontinuum source by using different bandwidth signals as the seed signal, and to study performance of supercontinuum source by different bandwidth seed signals for HNLF. Most commonly supercontinuum source was stressed ultra-short pulse laser system, we propose a tunable broadband source as the seed signals, and adjust different bandwidth seed signal into the HNLF, we also utilize SRS and SPM effect to shift energy. In addition we discussed the different seed signal for the nonlinear effects by adjusting the cavity length and polarization state, and change the erbium-doped fiber amplifier pump power for the nonlinear effects. The last we analysis the supercontinuum sources of the HNLFs with different lengths and dispersion values. The experimental results show that when using the broadband seed signal, the spectral is broader, and also show that when using the longer highly nonlinear fiber, which has broader spectral, and the overall flatness is better. When used the 1Km HNLF has best results, the spectra range of supercontinuum source is from 1180nm to 1700nm, which is above 518nm, the optimum flatness of supercontinuum is 30dB.
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Chen, Wei-Chih, and 陳韋志. "Supercontinuum generation in highly nonlinear fiber by well-defined laser pulses at 1550 nm." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/67s3kq.
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碩士國立交通大學
照明與能源光電研究所
106
We report the generation of supercontinuum by well-defined laser pulses at 1550 nm through a piece of 1-meter highly nonlinear fiber. The laser pulses at 19 MHz repetition rate were amplified to an average power of 5.22 W by the pre-amplifier and the booster, and the pulse duration is 23.1 ps. The supercontinuum has an optical spectrum spanning from 1020 to 2153 nm, and its average power is 3.34 W.
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Spillane, Sean Michael. "Fiber-Coupled Ultra-High-Q Microresonators for Nonlinear and Quantum Optics." Thesis, 2004. https://thesis.library.caltech.edu/2348/1/thesis.pdf.
Full textAbstract:
The ability to confine optical energy in small volumes for long periods of time is desirable for a number of applications, ranging from photonics and nonlinear optics, to fundamental studies in quantum electrodynamics. Whispering-gallery-mode microresonators are a promising cavity to study, due to the ability to obtain quality factors exceeding 100 million in micron-scale volumes. This thesis investigates the suitability of ultra-high-quality factor silica microresonators (both silica microspheres and silica toroidal microresonators) for nonlinear and quantum optics. Crucial to the actual use of these structures is the ability to efficiently excite and extract optical energy. The first part of this thesis investigates the ability to achieve near lossless coupling between a fiber-taper waveguide and a silica microresonator. It is shown that a coupling ideality (which is the fraction of energy coupled into the desired fiber mode) in excess of 99.97% is possible, meaning that optical energy can be coupled both to and from the optical resonator with near perfect efficiency.
Using tapered fibers, low threshold stimulated Raman scattering is observed in both silica microspheres and silica microtoroids at record low incident pump powers below 100 microwatts, much lower than previous devices. High conversion efficiencies (>35%) are also realized. Furthermore, the conditions for optimized performance of both stimulated Raman scattering and parametric oscillation in a microcavity are described.
Lastly, the suitability of toroidal microcavities for strong coupling cavity quantum electrodynamics is investigated. Numerical modeling of the optical modes demonstrates a significant reduction of modal volume with respect to spherical cavities, while retaining high quality factors. The extra degree of freedom of toroid microcavities can be used to achieve improved strong-coupling characteristics, and numerical results for atom-cavity coupling strength, critical atom number and critical photon numbers for cesium are calculated and shown to exceed values currently possible using Fabry-Perot cavities. Modeling predicts atom-cavity coupling rates exceeding 700 MHz and critical atom numbers approaching 10⁻⁷.
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Fernandes, Marco André Tavares. "Digital pre-distortion for 5G transmission over high-capacity optical fronthaul fiber links." Master's thesis, 2019. http://hdl.handle.net/10773/29568.
Full textAbstract:
The new generations of radio communications bring many challenges for
the fronthaul transport. While demanding larger capacity than previous
generations, low cost, low complexity, low power consumption and low
latency are required characteristics. This thesis explores the possibility
of using analog radio-over-fiber (RoF) fronthaul transmission in a
centralized-radio access network. We propose and study the use of low-cost
transceivers based on commercially available small form-factor pluggable
(SFP) transceivers adapted to transport analog signals.
The transceiver performance is experimentally characterized both with 4G
LTE and 5G signals. The studies of this thesis include the impact of the
carrier frequency, transmitted RF power, received optical power as well as
distance of the fiber link. Additionally, the benefits of a low-complexity
memory polynomial-based nonlinear compensation are evaluated. This
nonlinear compensation enables high-performance 5G operation yielding
an EVM < 3.5% in frequency region 1 (FR1) with 100 MHz bandwidth,
which is below the limits speci ed by 3GPP for 256QAM transmission . In
addition it also reduces the EVM from 5.7% to 5.4% when transmitting
over 20 km a FR2 400 MHz 5G signal at an intermediate carrier frequency
of 3.5 GHz.A nova geração de comunicações rádio traz muitos desafios para o transporte destes mesmos sinais. Enquanto que é exigida maior capacidade, os requisitos para complexidade, custo, consumo de potência e latência são mais estritos. Esta dissertação explora a possibilidade de usar transmissão analógica de sinais rádio sobre fibra em redes de acesso centralizadas. _E proposto e estudado o uso de transmissores óticos de baixo custo baseados em transmissores SFP adaptados para transportar sinais analógicos. A performance dos transmissores é caracterizada experimentalmente com sinais 4G e 5G. Os campos de estudo desta dissertação incluem o impacto da frequência da portadora, a potência RF transmitida, a potência ótica recebida e o comprimento da fibra. Adicionalmente, os benefícios de usar um polinômio com memória para compensação não linear são avaliados. Esta compensação não linear permite operações 5G de elevada performance obtendo um EVM inferior a 3.5% para sinais na região de frequências 1 com 100 MHz de largura de banda, o que é inferior aos limites estabelecidos pelo 3GPP para transmissão 256QAM. Adicionalmente uma redução de EVM de 5.7% para 5.4% é verificada quando se transmite um sinal 5G FR2 com 400 MHz de largura de banda por 20 km de fibra.
Mestrado em Engenharia Eletrónica e Telecomunicações
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Tavassoli, Vahid. "High capacity phase/amplitude modulated optical communication systems and nonlinear inter-channel impairments." Thesis, 2012. http://hdl.handle.net/1828/3889.
Full textAbstract:
This thesis studies and mathematically models nonlinear interactions among channels
of modern high bit rate (amplitude/) phase modulated optical systems. First,
phase modulated analogue systems are studied and a differential receiving method is
suggested with experimental validation. The main focus of the rest of the thesis is
on digital advanced modulation format systems. Cross-talk due to fiber Kerr nonlinearity
in two-format hybrid systems as well as 16-QAM systems is mathematically
modelled and verified by simulation for different system parameters. A comparative
study of differential receivers and coherent receivers is also given for hybrid systems.
The model is based on mathematically proven assumptions and provides an intuitive
analytical understanding of nonlinear cross-talk in such systems.Graduate
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Ben, Braham Fatma. "Contribution à l’étude théorique et expérimentale d’un oscillateur laser fonctionnant en régime impulsionnel dans les bandes spectrales C et L." Thesis, 2018. http://www.theses.fr/2018ANGE0025/document.
Full textAbstract:
Ce travail de thèse concerne le développement d’un laser à fibre générant des impulsions rectangulaires très énergétiques et accordables à l’échelle du temps et des impulsions géantes à haute énergie. En premier temps,nous avons développé un modèle numérique pour étudier la génération des impulsions rectangulaires dans un laser à fibre en forme de huit à double amplificateur.L’objectif est de montrer l’impact de l’effet non linéaire induit par la fibre micro structurée sur le contrôle de la durée d’impulsion rectangulaire générée par le laser. Un ensemble de paramètres laser nous a permis ainsi de générer des impulsions rectangulaires à haute énergie dans le régime de la résonance du soliton dissipatif (DSR). En plus, plusieurs expériences ont été mises en place pour optimiser la génération de l’impulsion DSR en termes d’énergie et de durée.Toujours sur le plan expérimental, des impulsions géantes à haute énergie à partir du laser à fibre verrouillé en phase couplé à un retard optique ont été obtenues. Cela nous a permis de générer une large plage de durée d’impulsion à l'échelle de μs à taux de répétition faible dans des cavités utilisant des absorbants saturables artificielsThis work deals with the development of a fiber laser generating high energy and width tunable square pulses and high-energy giant pulses. First, we have developed a numerical model to study the generation of rectangular pulses in a double amplifier fiber laser. The objective is to study the impact of the non-linear effect induced by the microstructured optical fiber on the control of the square pulse duration. A set of laser parameters allowed us to generate high energy square pulses in the dissipative soliton resonance (DSR) regime. In addition, several experiments have been set up to optimize the generation of the DSR pulse in terms of energy and duration. Experimentally, high energy giant pulses from a passively mode-locked fiber ring laser coupled to a long external cavity are obtained. This allowed us to generate a wide range of pulse duration of μs at a low repetition rate in cavities using artificial saturable absorbers
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Neumann, Niels. "Signal processing with optical delay line filters for high bit rate transmission systems." Doctoral thesis, 2010. https://tud.qucosa.de/id/qucosa%3A25472.
Full textAbstract:
In den letzten Jahrzehnten ist das globale Kommunikationssystem in einem immer größerem Maße ein integraler Bestandteil des täglichen Lebens geworden. Optische Kommunikationssysteme sind die technologische Basis für diese Entwicklung. Nur Fasern können die riesige benötigte Bandbreite bereitstellen. Während für die ersten optischen Übertragungssysteme die Faser als "flacher" Kanal betrachtet werden konnte, machen Wellenlängenmultiplex und steigende Übertragungsraten die Einbeziehung von immer mehr physikalischen Effekten notwendig. Bei einer Erhöhung der Kanaldatenrate auf 40 Gbit/s und mehr ist die statische Kompensation von chromatischer Dispersion nicht mehr ausreichend. Die intrinsische Toleranz der Modulationsformate gegenüber Dispersion nimmt quadratisch mit der Symbolrate ab. Daher können beispielsweise durch Umwelteinflüsse hervorgerufene Dispersionsschwankungen die Dispersionstoleranz der Modulationsformate überschreiten. Dies macht eine adaptive Dispersionskompensation notwendig, was gleichzeitig auch Dispersionsmonitoring erfordert, um den adaptiven Kompensator steuern zu können. Vorhandene Links können mit Restdispersionskompensatoren ausgestattet werden, um sie für Hochgeschwindigkeitsübertragungen zu ertüchtigen.
Optische Kompensationstechniken sind unabhängig von der Kanaldatenrate. Daher wird eine Erhöhung der Datenrate problemlos unterstützt. Optische Kompensatoren können WDM-fähig gebaut werden, um mehrere Kanäle auf einmal zu entzerren. Das Buch beschäftigt sich mit optischen Delay-Line-Filtern als eine Klasse von optischen Kompensatoren. Die Filtersynthese von solchen Delay-Line-Filtern wird behandelt. Der Zusammenhang zwischen optischen Filtern und digitalen FIR-Filtern mit komplexen Koeffizienten im Zusammenhang mit kohärenter Detektion wird aufgezeigt. Iterative und analytische Methoden, die die Koeffizienten für dispersions- und dispersions-slope-kompensierende Filter produzieren, werden untersucht. Genauso wichtig wie die Kompensation von Dispersion ist die Schätzung der Dispersion eines Signals. Mit Delay-Line-Filtern können die Restseitenbänder eines Signals genutzt werden, um die Dispersion zu messen. Alternativ kann nichtlineare Detektion angewandt werden, um die Pulsverbreiterung, die hauptsächlich von der Dispersion herrührt, zu schätzen. Mit gemeinsamer Dispersionskompensation und Dispersionsmonitoring können Dispersionskompensatoren auf die Signalverzerrungen eingestellt werden. Spezielle Eigenschaften der Filter zusammen mit der analytischen Beschreibung können genutzt werden, um schnelle und zuverlässige Steueralgorithmen zur Filtereinstellung bereitzustellen. Schließlich wurden Prototypen derartiger faseroptischen Kompensatoren von chromatischer Dispersion und Dispersions-Slope hergestellt und charakterisiert. Die Einheiten und ihr Systemverhalten wird gezeigt und diskutiert.Over the course of the past decades, the global communication system has become a central part of people's everyday lives. Optical communication systems are the technological basis for this development. Only fibers can provide the huge bandwidth that is required. Where the fiber could be regarded as a flat channel for the first optical transmission systems wavelength multiplexing and increasing line rates made it necessary to take more and more physical effects into account. When the line rates are increased to 40 Gbit/s and higher static chromatic dispersion compensation is not enough. The modulation format's intrinsic tolerance for dispersion decreases quadratically with the symbol rate. Thus, environmentally induced chromatic dispersion fluctuations may exceed the dispersion tolerance of the modulation formats. This makes an adaptive dispersion compensation necessary implying also the need for a monitoring scheme to steer the adaptive compensator. Legacy links that are CD-compensated by DCFs can be upgraded with residual dispersion compensators to make them ready for high speed transmission. Optical compensation is independent from the line rate. Hence, increasing the data rates is inherently supported. Optical compensators can be built WDM ready compensating multiple channels at once. The book deals with optical delay line filters as one class of optical compensators. The filter synthesis of such delay line filters is addressed. The connection between optical filters and digital FIR filters with complex coefficients that are used in conjunction with coherent detection could be shown. Iterative and analytical methods that produce the coefficients for dispersion (and also dispersion slope) compensating filters are researched. As important as the compensation of dispersion is the estimation of the dispersion of a signal. Using delay line filters, the vestigial sidebands of a signal can be used to measure the dispersion. Alternatively, nonlinear detection can be used to estimate the pulse broadening which is caused mainly by dispersion. With dispersion compensation and dispersion monitoring, dispersion compensators can be adapted to the signal's impairment. Special properties of the filter in conjunction with an analytical description can be used to provide a fast and reliable control algorithm for setting the filter to a given dispersion and centering it on a signal. Finally, prototypes of such fiber optic chromatic dispersion and dispersion slope compensation filters were manufactured and characterized. The device and system characterization of the prototypes is presented and discussed.