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1
Alalak, Tamara, and Haider Y. Hammod. "Employment the Laser to Fabricate the Surface Plasmon Resonance Sensor." Ibn AL-Haitham Journal For Pure and Applied Sciences 36, no. 2 (April 20, 2023): 171–80. http://dx.doi.org/10.30526/36.2.3002.
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The Optical Fiber sensor based on the Surface Plasmon Resonance (SPR) technology hasbeen a successful performance sensing and presents high sensitivity. This thesis investigates theperformance of several structure of SPR sensor in field of refractive index and chemicalapplications. A structure of Multi-Mode Fiber- Single Mode Fiber- Multi Mode Fiber (MMFSMF-MMF)
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Yang, Fan, Liqiang Zhang, Chenglin Bai, Shijie Ren, Zhen Tian, Yicun Yao, and Minghong Wang. "Yb-Doped Mode-Locked Fiber Laser Based on an All-Fiber Interferometer Filter." Photonics 10, no. 2 (February 13, 2023): 203. http://dx.doi.org/10.3390/photonics10020203.
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An interference filter is designed by fusing a segment of multi-core fiber (MCF) between two segments of multimode fibers (MMFs), which is then spliced between two segments of single mode fibers (SMFs). The light is split into the cladding and different cores of the MCF through the first segment of MMF, which is then coupled back into the core of SMF by the second segment of MMF. When the lengths of MCF are selected to be 4 mm and 10 mm, the 3 dB bandwidths of the filters around 1060 nm are 8.40 nm and 4.84 nm, respectively. Applying these filters in an Yb-doped fiber laser mode-locked by nonlinear polarization rotation, stable pulses have been obtained. Compared with the reported interference filters, the filter proposed in this paper has the advantages of simple fabrication process, compact structure and high environmental stability.
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Bourdine, Anton V., Vladimir A. Burdin, Vijay Janyani, Ashish Kumar Ghunawat, Ghanshyam Singh, and Alexander E. Zhukov. "Design of Silica Multimode Optical Fibers with Extremely Enlarged Core Diameter for Laser-Based Multi-Gigabit Short-Range Optical Networks." Photonics 5, no. 4 (October 16, 2018): 37. http://dx.doi.org/10.3390/photonics5040037.
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This work presents an alternative fast and simple method for the design of a refractive index profile of silica multimode optical fibers (MMFs) with extremely enlarged core diameters of up to 100 µm for laser-based multi-gigabit short-range optical networks. We demonstrate some results of 100 µm core MMF graded index profile optimization performed by a proposed solution, which provides a selected mode staff differential mode delay (DMD) reduction over the “O”-band under particular launching conditions. Earlier on, a developed alternative model for a piecewise regular multimode fiber optic link operating in a few-mode regime for the computation of laser-excited optical pulse dynamics during its propagation over an irregular silica graded-index MMF with an extremely large core diameter, is utilized to estimate the potentiality of fiber optic links with the described MMFs. Here, we also present the comparison results of the simulation of 10GBase-LX optical signal transmission over 100 µm core MMFs with conventional and optimized graded-index refractive index profiles.
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Yahyaoui, Moussa El, Ali El Moussati, and Kamel Haddadi. "Performance Evaluation of 60-GHz-WPAN System Distributed Over Multi-Mode Fiber." International Journal of Electronics and Telecommunications 63, no. 4 (November 27, 2017): 381–87. http://dx.doi.org/10.1515/eletel-2017-0052.
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Abstract The manuscript deals with the assessment of Radio over Fiber (RoF) system including pure electrical baseband, pure radio frequency band centered around 60 GHz, and hybrid radio-optical system at the same RF band using a global simulation. In this work we focus on RoF solution to improve the low coverage of the 60 GHz channel caused by high free-space attenuation. A realistic co-simulation of the Wireless Personal Area Network (WPAN) IEEE802.15.3c-RoF was performed in a residential environment for Line-Of-Sight (LOS) and Non-Line- Of-Sight (NLOS). In this work, we demonstrated a 60 GHz radio on Multi-Mode Fiber (MMF) using Optical Carrier Suppression (OCS) modulation. The BER (Bit Error Ratio) performance of this system is measured by varying the following parameters: optical launched power, fiber length, modulation format, Channel coding and Signal to Noise Ratio. We show that the RoF at 60 GHz can reach a minimum of 300 m of MMF without optical amplifiers followed by a 5 m wireless transmission with BER less than 10-3 in the LOS and NLOS environments.
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Elhajrat, N., O. Elouatssi, A. El Abbassi, F. Essahlaoui, and M. Aftatah. "Study of Optical MIMO Transmission Systems Using the MGDM Multiplexing Technique." Modern Applied Science 14, no. 1 (December 26, 2019): 34. http://dx.doi.org/10.5539/mas.v14n1p34.
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In current local area networks, multimode fibers (MMFs), mainly graded index (GI) MMFs, are the main types of fibers used for data communications. Because of their high bandwidth, they are considered the main method of transmission that allows to offer multiservice broadband services using optical multiplexing techniques.
The MGDM (ModeGroup Division Multiplexing) is a Multiplexing technique, which aims to improve the performance of the multimode optical fiber by spatially multiplexing the data streams to be transmitted. In this work, we study optical MIMO (multi-input multi-output) transmission systems on an MMF optical fiber, specifically the adaptation of the architecture of MIMO transmission systems. In this context, we have studied the mode group multiplexing technique (MDGM), to evaluate the transmission capacity. In fact, the latter depends on the injection conditions and the state of the optical fiber.
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Lu, Lidong, Xingchen Su, Chenglong Zhang, Qinghao Gao, and Hongwei Yang. "A Novel Distributed Vibration Sensor Based on Fading Noise Reduction in Multi-Mode Fiber." Sensors 22, no. 20 (October 20, 2022): 8028. http://dx.doi.org/10.3390/s22208028.
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Multi-mode fiber (MMF) is used in a polarization-sensitive optical time domain reflectometer (OTDR) for vibration event location and spectrum analysis. The vibration events acting on MMF are considered to be the optical polarization state and phase diversifying process for fading noise reduction. In addition, data averaging with continuous positions and the fast Fourier transform (FFT) method is proposed to extract the spectrum of the vibration events. In the experiment, the vibration events are loaded at the positions of 5.167 and 10.145 km, respectively, along MMF. The experimental results demonstrate that the vibration event can effectively diversify the optical polarization state and phase of the Rayleigh scattering light to make the averaged OTDR trace behind the vibration position converge rapidly, which helps to locate corresponding vibration events and extract the vibration spectrum. It is inferred that the new distributed vibration sensor shall have a lower false alarm rate, as it can greatly reduce the errors caused by randomness of the sensing light signals. Additionally, it also saves time in comparison with the method that analyzes the vibration spectra for all the positions along the fiber under test.
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Rahmani, Babak, Ilker Oguz, Ugur Tegin, Jih-liang Hsieh, Demetri Psaltis, and Christophe Moser. "Learning to image and compute with multimode optical fibers." Nanophotonics 11, no. 6 (January 21, 2022): 1071–82. http://dx.doi.org/10.1515/nanoph-2021-0601.
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Abstract Multimode fibers (MMF) were initially developed to transmit digital information encoded in the time domain. There were few attempts in the late 60s and 70s to transmit analog images through MMF. With the availability of digital spatial modulators, practical image transfer through MMFs has the potential to revolutionize medical endoscopy. Because of the fiber’s ability to transmit multiple spatial modes of light simultaneously, MMFs could, in principle, replace the millimeters-thick bundles of fibers currently used in endoscopes with a single fiber, only a few hundred microns thick. That, in turn, could potentially open up new, less invasive forms of endoscopy to perform high-resolution imaging of tissues out of reach of current conventional endoscopes. Taking endoscopy by its general meaning as looking into, we review in this paper novel ways of imaging and transmitting images using a machine learning approach. Additionally, we review recent work on using MMF to perform machine learning tasks. The advantages and disadvantages of using machine learning instead of conventional methods is also discussed. Methods of imaging in scattering media and particularly MMFs involves measuring the phase and amplitude of the electromagnetic wave, coming out of the MMF and using these measurements to infer the relationship between the input and the output of the MMF. Most notable techniques include analog phase conjugation [A. Yariv, “On transmission and recovery of three-dimensional image information in optical waveguides,” J. Opt. Soc. Am., vol. 66, no. 4, pp. 301–306, 1976; A. Gover, C. Lee, and A. Yariv, “Direct transmission of pictorial information in multimode optical fibers,” J. Opt. Soc. Am., vol. 66, no. 4, pp. 306–311, 1976; G. J. Dunning and R. Lind, “Demonstration of image transmission through fibers by optical phase conjugation,” Opt. Lett., vol. 7, no. 11, pp. 558–560, 1982; A. Friesem, U. Levy, and Y. Silberberg, “Parallel transmission of images through single optical fibers,” Proc. IEEE, vol. 71, no. 2, pp. 208–221, 1983], digital phase conjugation [I. N. Papadopoulos, S. Farahi, C. Moser, and D. Psaltis, “Focusing and scanning light through a multimode optical fiber using digital phase conjugation,” Opt. Express, vol. 20, no. 10, pp. 10583–10590, 2012; I. N. Papadopoulos, S. Farahi, C. Moser, and D. Psaltis, “High-resolution, lensless endoscope based on digital scanning through a multimode optical fiber,” Biomed. Opt. Express, vol. 4, no. 2, pp. 260–270, 2013] or the full-wave holographic transmission matrix method. The latter technique, which is the current gold standard, measures both the amplitude and phase of the output patterns corresponding to multiple input patterns to construct a matrix of complex numbers relaying the input to the output [Y. Choi, et al., “Scanner-free and wide-field endoscopic imaging by using a single multimode optical fiber,” Phys. Rev. Lett., vol. 109, no. 20, p. 203901, 2012; A. M. Caravaca-Aguirre, E. Niv, D. B. Conkey, and R. Piestun, “Real-time resilient focusing through a bending multimode fiber,” Opt. Express, vol. 21, no. 10, pp. 12881–12887; R. Y. Gu, R. N. Mahalati, and J. M. Kahn, “Design of flexible multi-mode fiber endoscope,” Opt. Express, vol. 23, no. 21, pp. 26905–26918, 2015; D. Loterie, S. Farahi, I. Papadopoulos, A. Goy, D. Psaltis, and C. Moser, “Digital confocal microscopy through a multimode fiber,” Opt. Express, vol. 23, no. 18, pp. 23845–23858, 2015]. This matrix is then used for imaging of the inputs or projection of desired patterns. Other techniques rely on iteratively optimizing the pixel value of the input image to perform a particular task (such as focusing or displaying an image) [R. Di Leonardo and S. Bianchi, “Hologram transmission through multi-mode optical fibers,” Opt. Express, vol. 19, no. 1, pp. 247–254, 2011; T. Čižmár and K. Dholakia, “Shaping the light transmission through a multimode optical fibre: complex transformation analysis and applications in biophotonics,” Opt. Express, vol. 19, no. 20, pp. 18871–18884, 2011; T. Čižmár and K. Dholakia, “Exploiting multimode waveguides for pure fibre-based imaging,” Nat. Commun., vol. 3, no. 1, pp. 1–9, 2012; S. Bianchi and R. Di Leonardo, “A multi-mode fiber probe for holographic micromanipulation and microscopy,” Lab Chip, vol. 12, no. 3, pp. 635–639, 2012; E. R. Andresen, G. Bouwmans, S. Monneret, and H. Rigneault, “Toward endoscopes with no distal optics: video-rate scanning microscopy through a fiber bundle,” Opt. Lett., vol. 38, no. 5, pp. 609–611, 2013].
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Mohammed, Zahraa H., Radhi Sehen Issa, and Sadiq Ahmed. "Studying the effect of changing Input conditions on MMF using MGDM technique." Bulletin of Electrical Engineering and Informatics 11, no. 6 (December 1, 2022): 3361–67. http://dx.doi.org/10.11591/eei.v11i6.4340.
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The mode group diversity multiplexing (MGDM) multicast technology uses optical multiple input and output (O-MIMO) technology to provide greater capacity and the ability to transmit information over multi-mode fiber (MMF). The MGDM system has a benefit in terms of capacity expansion, which led to interest in its use in most optical communications. The MGDM exploits the optical fiber bandwidth by inserting spatial light detection, which increases the capacity of the MMF. This research aims to study the optical systems used for the MGDM technology, and to identify the methods of their analysis and design of O-MIMO systems to increase the amplitude of this signal. The conditions of light entry into the optical fiber such as typical spot size, radial displacements, angle, wavelength, and radius of the detectors sections are improved. Numerical MATLAB simulation is used to improve the amplitude of graded index multimode fiber (GI-MMF) and compared to the existing aggregation systems. Moreover, this method was simulated to improve the input and detection conditions to increase the O-MIMO capacity using the MGDM technique. Finally, the capacity of the MGDM system was studied and compared with different channels, and it is noticed that the capacity of the system increases with increasing the number of channels.
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Li, Jinze, Xin Liu, Hao Sun, Liming Wang, Jianqi Zhang, Li Deng, and Tianhong Ma. "An Optical Fiber Sensor Coated with Electrospinning Polyvinyl Alcohol/Carbon Nanotubes Composite Film." Sensors 20, no. 23 (December 7, 2020): 6996. http://dx.doi.org/10.3390/s20236996.
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A fiber-optics tapered sensor that is covered by an electrospinning polyvinyl alcohol (PVA) nanofiber film, is demonstrated to measure humidity and temperature simultaneously. A section multi-mode fiber (MMF) was sandwiched between two leading-in and out single mode fibers (SMFs), which was further tapered down to 29 μm to promote the humidity sensitivity of the sensor. A thin layer of electrospinning PVA nanofiber film was uniformly coated on the MMF taper region by electrospinning technology. In order to promote the humidity sensitivity and mechanical strength of electrospinning nanofibers, the carbon nanotubes (CNTs) were mixed into PVA to formed PVA/CNTs composite nanofiber film. A Fiber Bragg Grating (FBG) was cascaded with the humidity sensing fiber to monitor the ambient temperature simultaneously. The addition of CNTs effectively eliminated the cracks on the electrospinning nanofiber and made it more uniform and smoother. As experimental results show, the humidity sensitivity of the sensor with PVA/CNTs film was 0.0484 dB/%RH, an improvement of 31.16% compared to that of the sensor with PVA film, for which sensitivity is 0.0369 dB/%RH. The nanofiber humidity-sensitive film constructed using electrospinning had a satisfactory humidity response, special 3D structure and extensive application prospect.
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Becker, Thomas, Olaf Ziemann, Rainer Engelbrecht, and Bernhard Schmauss. "Optical Strain Measurement with Step-Index Polymer Optical Fiber Based on the Phase Measurement of an Intensity-Modulated Signal." Sensors 18, no. 7 (July 17, 2018): 2319. http://dx.doi.org/10.3390/s18072319.
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Polymer optical fibers (POFs) have been proposed for optical strain sensors due to their large elastic strain range compared to glass optical fibers (GOFs). The phase response of a single-mode polymer optical fiber (SM-POF) is well-known in the literature, and depends on the physical deformation of the fiber as well as the impact on the refractive index of the core. In this paper, we investigate the impact of strain on a step-index polymer optical fiber (SI-POF). In particular, we discuss the responsivity of an optical strain sensor which is based on the phase measurement of an intensity-modulated signal. In comparison to the phase response of an SM-POF, we must take additional influences into account. Firstly, the SI-POF is a multi-mode fiber (MMF). Consequently, we not only consider the strain dependence of the refractive index, but also its dependency on the propagation angle θz. Second, we investigate the phase of an intensity-modulated signal. The development of this modulation phase along the fiber is influenced by modal dispersion, scattering, and attenuation. The modulation phase therefore has no linear dependency on the length of the fiber, even in the unstrained state. For the proper consideration of these effects, we rely on a novel model for step-index multi-mode fibers (SI-MMFs). We expand the model to consider the strain-induced effects, simulate the strain responsivity of the sensor, and compare it to experimental results. This led to the conclusion that the scattering behavior of a SI-POF is strain-dependent, which was further proven by measuring the far field at the end of a SI-POF under different strain conditions.
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Rothe, Stefan, Hannes Radner, Nektarios Koukourakis, and Jürgen W. Czarske. "Transmission Matrix Measurement of Multimode Optical Fibers by Mode-Selective Excitation Using One Spatial Light Modulator." Applied Sciences 9, no. 1 (January 8, 2019): 195. http://dx.doi.org/10.3390/app9010195.
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Multimode fibers (MMF) are promising candidates to increase the data rate while reducing the space required for optical fiber networks. However, their use is hampered by mode mixing and other effects, leading to speckled output patterns. This can be overcome by measuring the transmission matrix (TM) of a multimode fiber. In this contribution, a mode-selective excitation of complex amplitudes is performed with only one phase-only spatial light modulator. The light field propagating through the fiber is measured holographically and is analyzed by a rapid decomposition method. This technique requires a small amount of measurements N, which corresponds to the degree of freedom of the fiber. The TM determines the amplitude and phase relationships of the modes, which allows us to understand the mode scrambling processes in the MMF and can be used for mode division multiplexing.
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Safarloo, Sahar, Alberto Tapetado, and Carmen Vázquez. "Experimental Validation of High Spatial Resolution of Two-Color Optical Fiber Pyrometer." Sensors 23, no. 9 (April 27, 2023): 4320. http://dx.doi.org/10.3390/s23094320.
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Taking non-contact temperature measurements in narrow areas or confined spaces of non-uniform surfaces requires high spatial resolution and independence of emissivity uncertainties that conventional cameras can hardly provide. Two-color optical fiber (OF) pyrometers based on standard single-mode (SMF) and multi-mode optical fibers (MMF) with a small core diameter and low numerical aperture in combination with associated commercially available components can provide a spatial resolution in the micrometer range, independent of the material’s emissivity. Our experiment involved using a patterned microheater to generate temperatures of approximately 340 °C on objects with a diameter of 0.25 mm. We measured these temperatures using two-color optical fiber pyrometers at a 1 kHz sampling rate, which were linearized in the range of 250 to 500 °C. We compared the results with those obtained using an industrial infrared camera. The tests show the potential of our technique for quickly measuring temperature gradients in small areas, independent of emissivity, such as in microthermography. We also report simulations and experiments, showing that the optical power gathered via each channel of the SMF and MMF pyrometers from hot objects of 250 µm is independent of distance until the OF light spot becomes larger than the diameter of the object at 0.9 mm and 0.4 mm, respectively.
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Singh, Jasmeet, Andreas Ahrens, and Steffen Lochmann. "Joint Pre- and Post-Equalization with Higher-Order Modulation Formats in SDM-Based Optical MIMO Systems." Photonics 9, no. 11 (November 19, 2022): 876. http://dx.doi.org/10.3390/photonics9110876.
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The multiple-input and multiple-output (MIMO) technology is a promising area of research to cope up with the demands of higher data rates and capacity. In the optical communication domain, the combination of space-division multiplexing (SDM) with higher-order modulation (HOM) formats over an optical MIMO system actively addresses these challenges. By allowing multi-level signaling with limited increment in the transmitter’s complexity, a jointly designed pre- and post-equalization (PPE) for an optical MIMO system with a multi-mode fiber (MMF) link is proposed. Cost-effectiveness of the system is incorporated by utilizing intensity modulation/direct detection (IM/DD) with HOM formats such as pulse-amplitude modulation (PAM) schemes. With the aid of a numerical optimization algorithm, the proposed joint-PPE filter coefficients are optimized with respect to the MMF channel and the transmit power constraint. In contrast to existing research on the single-mode fiber (SMF) based optical systems, the effectiveness of the proposed joint-PPE filter is analyzed on an MMF link, which is considerably degraded by the modal dispersion. In the analyzed experimental scenario, the proposed joint-PPE scheme confirms to be beneficial as compared to the post-equalization only (PE-only) in terms of bit-error rate (BER) performance. Furthermore, the required average received optical power to reach a BER 10−4 by the joint-PPE scheme is improved by 2 dB with comparison to the minimum mean-squared error (MMSE) PE-only.
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Khattak, Anum, Gerard Tatel, and Li Wei. "Tunable and Switchable Erbium-Doped Fiber Laser Using a Multimode-Fiber Based Filter." Applied Sciences 8, no. 7 (July 13, 2018): 1135. http://dx.doi.org/10.3390/app8071135.
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We demonstrated a compact tunable and switchable single/dual-wavelength erbium-doped fiber laser. The fiber laser can be tuned and switched from single-wavelength to dual-wavelength oscillation by using our recently proposed tunable comb filter. The comb filter consists of a section of multimode fiber (MMF) coiled into a polarization controller and two sections of single mode fibers (SMFs) to form a SMF/MMF/SMF structure, serving as a simple tunable all-fiber Mach-Zehnder interferometer. Due to the insertion of the MMF-based polarization controller (PC), an additional phase shift is introduced from the difference of the birefringence intensity in different dominant modes, which can be used to tune the fiber laser. In the experiment, by properly adjusting the PC, a tuning range of 9.3 nm can be achieved for the single-wavelength operation. Moreover, dual-wavelength operation with different free-spectral-ranges can be obtained. The tunable and switchable fiber lasers are of great importance for their applications in optical testing, optical fiber sensing, and signal processing.
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Dreyer, Uilian José, Aritz Ozcariz, Joaquín Ascorbe, Pablo Zubiate, Ignacio Vitoria, Cicero Martelli, Jean Carlos Cardozo da Silva, and Carlos Ruiz Zamarreño. "Gas Detection Using LMR-Based Optical Fiber Sensors." Proceedings 2, no. 13 (November 21, 2018): 890. http://dx.doi.org/10.3390/proceedings2130890.
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This work presents a first approach to the utilization of Lossy Mode Resonance (LMR) based optical fiber sensors for gas detection. The optical sensor is based on a SnO2 thin-film fabricated onto the core of cladding removed multimode fibers (MMF). The time response of the device to four different gases (NH3, NO, CO2 and O2) was monitored obtaining the best sensitivity for NO whereas the response to NH3 revealed the best repeatability.
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Scharf, Elias, Robert Kuschmierz, and Jürgen Czarske. "Holographic lensless fiber endoscope with needle size using self-calibration." tm - Technisches Messen 86, no. 3 (March 26, 2019): 144–50. http://dx.doi.org/10.1515/teme-2018-0087.
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AbstractEndoscopes enable optical keyhole access in many applications for instance in biomedicine. In general, coherent fiber bundles (CFB) are used in conjunction with rigid lens systems which determine a fixed image plane. However, the lens system limits the minimum diameter of the endoscope typically to several millimeters. Additionally, only pixelated two-dimensional amplitude patterns can be transferred due to phase scrambling between adjacent cores. These limitations can be overcome by digital optical elements. Thus, in principle thinner, lensless, holographic endoscopes with a three-dimensional adjustable focus for imaging and illumination can be realized. So far, several techniques based on single mode CFB and multi mode fibers (MMF) have been presented. However, these techniques require access to both sides of the fiber, in order to calibrate the bending and temperature sensitive phase distortion, which is not possible in a real application. We present the feasibility of an in-situ calibration and compensation of a CFB with single sided access. A lensless endoscope with a diameter of only 500 µm, a spatial resolution around 1 µm and video rate capability is realized.
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Singh, Jasmeet, and Andreas Ahrens. "Joint-Transceiver Equalization Technique over a 1.4 km Multi-Mode Fiber Using Optical MIMO Technique in IM/DD Systems." Photonics 10, no. 6 (June 19, 2023): 696. http://dx.doi.org/10.3390/photonics10060696.
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In optical fiber communication, recent advances in multiple-input and multiple-output (MIMO) systems using space-division multiplexing have helped achieve higher spectral efficiency and data rates. Propagating higher-order modulation formats over MIMO systems further strengthens the capacity of the transmission link. In the optical-MIMO system, the dispersion impairments originating from a 1.4 km long multi-mode fiber (MMF) are mitigated using the proposed joint-transceiver equalization technique. A numerical convex optimization algorithm is used to compute and optimize the pre- and post-equalization (PPE) coefficients jointly restricted by cost and power budgets. The potential of the proposed joint-PPE technique is tested on an MMF link, which is severely degraded by dispersion compared to a single-mode fiber channel. From the experimental results, the average optical received power gain necessary to reach 10−4 bit-error rate is improved by nearly 2.5 dB using the joint-PPE compared to the post-equalization only based on the minimum mean-squared error principle. When the efficiency of the conventional zero-forcing (ZF) principle-based PPE and the joint-PPE is compared, the joint-PPE scheme outperforms the ZF-PPE by approximately 1.5 dB. The enhancement in the transmission quality is observed with experimentally measured eye diagrams using the joint-PPE scheme. Under the analyzed scenarios, computer simulation also confirms the hypothesis, which establishes the effectiveness of the proposed joint-transceiver equalization over the conventional ZF-PPE scheme. Moreover, the simulated performance benefits of the joint-PPE are evaluated using the singular value decomposition (SVD) technique. Improvement of ≈3.86 dB in the average optical received power gain required to reach 10−4 bit-error rate is witnessed with the PAM-4 format. Overall, the joint-transceiver equalization technique is proven to be beneficial in optical MIMO systems.
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Maria Eduarda Benfica Gonçalves, Rafael Andrade Vieira, Ciro Matheus de Lima Costa, Rafael Andrade Vieira, Jessica Guerreiro Santos Ramalho, and Valéria Loureiro da Silva. "Optical Fibers Characterization for Macrobending Sensors." JOURNAL OF BIOENGINEERING, TECHNOLOGIES AND HEALTH 7, no. 1 (May 22, 2024): 51–56. http://dx.doi.org/10.34178/jbth.v7i1.366.
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The article delves into characterizing macrobending losses in optical fiber coils for use in diverse sensors. It examines Single-Mode Fiber (SMF) and Multimode Fiber (MMF) with step and graded index profiles incorporated into sensor coils of varying diameters and numbers of turns. The experimental configuration involves compressing the coils to monitor optical power loss caused by attenuation. The findings reveal that SMFs experience more significant macrobending losses than MMFs, while the graded index fiber exhibits notable resistance to bending. These results offer valuable guidance for fiber selection and sensor design considerations.
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Kern, Alexander, Sujoy Paul, Dietmar Wahl, Ahmed Al-Samaneh, and Rainer Michalzik. "Single-Fiber Bidirectional Optical Data Links with Monolithic Transceiver Chips." Advances in Optical Technologies 2012 (February 27, 2012): 1–8. http://dx.doi.org/10.1155/2012/729731.
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We report the monolithic integration, fabrication, and electrooptical properties of AlGaAs-GaAs-based transceiver (TRx) chips for 850 nm wavelength optical links with data rates of multiple Gbit/s. Using a single butt-coupled multimode fiber (MMF), low-cost bidirectional communication in half- and even full-duplex mode is demonstrated. Two design concepts are presented, based on a vertical-cavity surface-emitting laser (VCSEL) and a monolithically integrated p-doped-intrinsic-n-doped (PIN) or metal-semiconductor-metal (MSM) photodetector. Whereas the VCSEL-PIN photodiode (PD) chips are used for high-speed bidirectional data transmission over 62.5 and 50 μm core diameter MMFs, MSM TRx chips are employed for 100 or 200 μm large-area fibers. Such a monolithic transceiver design based on a well-established material system and avoiding the use of external fiber coupling optics is well suited for inexpensive and compact optical interconnects over distances of a few hundred meters. Standard MMF networks can thus be upgraded using high-speed VCSEL-PIN transceiver chips which are capable to handle data rates of up to 10 Gbit/s.
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Zhao, Jian, Yaping Liu, and Tianhua Xu. "Advanced DSP for Coherent Optical Fiber Communication." Applied Sciences 9, no. 19 (October 8, 2019): 4192. http://dx.doi.org/10.3390/app9194192.
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In this paper, we provide an overview of recent progress on advanced digital signal processing (DSP) techniques for high-capacity long-haul coherent optical fiber transmission systems. Not only the linear impairments existing in optical transmission links need to be compensated, but also, the nonlinear impairments require proper algorithms for mitigation because they become major limiting factors for long-haul large-capacity optical transmission systems. Besides the time domain equalization (TDE), the frequency domain equalization (FDE) DSP also provides a similar performance, with a much-reduced computational complexity. Advanced DSP also plays an important role for the realization of space division multiplexing (SDM). SDM techniques have been developed recently to enhance the system capacity by at least one order of magnitude. Some impressive results have been reported and have outperformed the nonlinear Shannon limit of the single-mode fiber (SMF). SDM introduces the space dimension to the optical fiber communication. The few-mode fiber (FMF) and multi-core fiber (MCF) have been manufactured for novel multiplexing techniques such as mode-division multiplexing (MDM) and multi-core multiplexing (MCM). Each mode or core can be considered as an independent degree of freedom, but unfortunately, signals will suffer serious coupling during the propagation. Multi-input–multi-output (MIMO) DSP can equalize the signal coupling and makes SDM transmission feasible. The machine learning (ML) technique has attracted worldwide attention and has been explored for advanced DSP. In this paper, we firstly introduce the principle and scheme of coherent detection to explain why the DSP techniques can compensate for transmission impairments. Then corresponding technologies related to the DSP, such as nonlinearity compensation, FDE, SDM and ML will be discussed. Relevant techniques will be analyzed, and representational results and experimental verifications will be demonstrated. In the end, a brief conclusion and perspective will be provided.
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Wang, Zeliang, André Sandmann, John G. McWhirter, and Andreas Ahrens. "Decoupling of Broadband Optical MIMO Systems Using the Multiple Shift SBR2 Algorithm." International Journal of Advances in Telecommunications, Electrotechnics, Signals and Systems 6, no. 1 (March 18, 2017): 30. http://dx.doi.org/10.11601/ijates.v6i1.207.
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Polynomial singular value decomposition (PSVD) plays a very important role in broadband multiple-input multiple-output (MIMO) systems. One of its applications lies in the decoupling of MIMO convolutive mixing channel matrixin order to recover the transmitted signals corrupted by the channel interference (CI) at the receiver. In this paper, a novel algorithm, known as multiple shift second order sequential best rotation (MS-SBR2), is proposed to compute the approximate PSVD of the broadband MIMO channel matrix. Experimental examples, including a measured (2 × 2) optical MIMO channel impulse response using the multi-mode fiber (MMF) testbed, are presented to examine the proposed algorithm. Bit error rate (BER) performances are evaluated among different transmission schemes. In addition, power allocation (PA) schemes are investigated to further optimize the BER performance.
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Mar-Abundis, Nailea, Yadira Aracely Fuentes-Rubio, René Fernando Domínguez-Cruz, and José Rafael Guzmán-Sepúlveda. "Sugar Detection in Aqueous Solution Using an SMS Fiber Device." Sensors 23, no. 14 (July 11, 2023): 6289. http://dx.doi.org/10.3390/s23146289.
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We report on the fabrication and testing of a fiber optics sensor based on multimodal interference effects, which aims at the detection of different types of sweeteners dissolved in water. The device, which has a simple structure, commonly known as the SMS configuration, is built by splicing a segment of commercial-grade, coreless multimode fiber (NC-MMF) between two standard single-mode fibers (SMFs). In this configuration, the evanescent field traveling outside the core of the NC-MMF allows the sensing of the refractive index of the surrounding media, making it possible to detect different levels of sugar concentration. The optical sensor was tested with aqueous solutions of glucose, fructose, and sucrose in the concentration range from 0 wt% to 20 wt% at room temperature. The proposed device exhibits a linear response with a sensitivity of 0.1835 nm/wt% for sucrose, 0.1687 nm/wt% for fructose, and 0.1694 nm/wt% for glucose, respectively, with a sensing resolution of around 0.5 wt%. Finally, we show that, despite having similar concentration behavior, some degree of discrimination between the different sugars can be achieved by assessing their thermo-optical response.
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Kumari, Meet, Abhishek Sharma, and Sushank Chaudhary. "High-Speed Spiral-Phase Donut-Modes-Based Hybrid FSO-MMF Communication System by Incorporating OCDMA Scheme." Photonics 10, no. 1 (January 15, 2023): 94. http://dx.doi.org/10.3390/photonics10010094.
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Hybrid free-space optics (FSO) and optical fiber have been viewed as vital transmission techniques to satisfy high bandwidth and extended transmission range requirements under adverse environment conditions in the future last-mile obstruction problem. In this investigation, 80 Gbps data is transmitted on a hybrid FSO and multimode fiber (MMF)-based network using mode division multiplexing of two donut modes, Donut mode 0 and 1, and optical code-division multiplexing (OCDMA) schemes. For the OCDMA schemes, modified new zero-cross-correlation (MNZCC) codes are used, whereas, to add the phases into donut modes, a spiral phase diffuser is used. The purpose of the investigation is to provide an economical, high-speed and advanced last-mile network with adequate resource utilization for hybrid wired/wireless-based systems. The results obtained show achievement of an acceptable BER up to a fixed 100 m FSO link, with the combination of a 385 m MMF link under clear weather conditions. In another case, when the MMF link was fixed at 100 m, an acceptable bit error rate (BER) is achieved at 2.07 km FSO link. Furthermore, the results were obtained in the presence of strong and weak turbulences. A comparison of log-normal and gamma-gamma modeling for scintillations is presented.
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Xiang, Qianyi, Nan Li, Xingfan Chen, Cheng Liu, and Huizhu Hu. "Miniaturized Dual-Beam Optical Trap Based on Fiber Pigtailed Focuser." Photonics 10, no. 9 (September 3, 2023): 1007. http://dx.doi.org/10.3390/photonics10091007.
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Optical traps, utilizing a laser to confine and manipulate microscopic particles, are widely employed in various scientific applications. We propose a miniaturized dual-beam fiber optical trap for acceleration sensing. It comprises two counter-propagating beams’ output from a customized pair of single-mode fiber pigtailed focusers (SMFPF). We investigate the correlation between the misalignment and the coupling efficiency of the SMFPF pair. By maximizing the coupling efficiency, the optimal alignment is achieved. A multimode fiber (MMF) is introduced to collect and transmit side-scattered light of a trapped microsphere for motion detection. By analyzing the experimental output signal, we acquire displacement information of the trapped microspheres under both aligned and misaligned conditions. This paper provides a simple and practical solution for the alignment of dual beams and the integration of the optical traps’ levitation and detection structure, which lay a solid foundation for the further miniaturization of dual-beam optical traps.
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Liu, Yifan, Panpan Yu, Yijing Wu, Ziqiang Wang, Yinmei Li, Jinyang Liang, Puxiang Lai, and Lei Gong. "Single-shot wide-field imaging in reflection by using a single multimode fiber." Applied Physics Letters 122, no. 6 (February 6, 2023): 063701. http://dx.doi.org/10.1063/5.0132123.
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A single multimode fiber (MMF) provides almost an ideal optical channel to constitute a hair-thin endoscope for minimally invasive biomedical imaging at depths in tissue, especially if the imaging operation can be performed with one single shot in reflection mode, which, however, remains challenging to date. In this work, we present single-shot wide-field reflectance imaging by using a single MMF as the illumination unit and imaging probe simultaneously. To achieve single-shot image capture, a reflection matrix of the fiber was built by a learning-assisted approach for the universal inverse conversion from the output amplitudes to the input amplitudes. The performance was tested by imaging more than 30 000 natural scenes projected by a digital micromirror device, and an averaged Pearson correlation coefficient over 0.84 with respect to the ground truth was achieved in the experiment. Furthermore, the ability to image dynamic scenes at a high frame rate of up to 180 frames per second was demonstrated together with real-time observation of a freely moving microneedle located at the distal end of the MMF. The proposed reflection-mode single-fiber imaging scheme paves the way for practical video-rate microendoscopy at depths in tissue in a minimally invasive manner.
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Lin, Yu-Hong, Chih-Hsien Cheng, Cheng-Ting Tsai, Wei-Li Wu, Kent D. Choquette, and Gong-Ru Lin. "Surface Photonic Crystal Engineering of a Multi-Mode VCSEL for a Bit-Loaded Broadband QAM-OFDM Data Link at 99 Gbit/s." Photonics 10, no. 5 (May 9, 2023): 549. http://dx.doi.org/10.3390/photonics10050549.
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Bit-loaded quadrature amplitude modulation-orthogonal frequency division multiplexing (QAM-OFDM) encoding and photonic-crystal-engineered multi-mode vertical-cavity surface-emitting lasers (MM-VCSELs) transmission performance are analyzed. Two different surface photonic-crystal designs are used to configure the core and cladding regions of MM-VCSELs, producing continuous-wave and digital-encoding outputs. These outputs are combined with the end-face-flattened OM5 multi-mode fiber (MMF) for 100 m short-reach transmission. The photonic-crystal (PhC) structure exhibits a spatial mode-filtering ability, supporting few or single-mode outputs from the MM-VCSEL. This helps reduce the modal dispersion during OM5-MMF transmission of the encoded data. Comparing the original MM-VCSEL with two different surface-photonic-crystal-configured MM-VCSELs, the allowable bit-loaded QAM-OFDM data rate can be increased from 60.7 (for the VCSEL without the PhC structure) to 85/65 Gbit/s (for the PhC VCSELs with 2-layer PhC structures in the cladding layer and the ones with a 1-layer PhC structure in the core layer and 2-layer PhC structures in the cladding layer, respectively) under back-to-back (BtB) encoding and enable the 100 m OM5-MMF transmission to increase from 58.5 (for the VCSEL without the PhC structure) to 81.2/64.6 Gbit/s (for the PhC VCSELs with 2-layer PhC structures in the cladding layer and the ones with a 1-layer PhC structure in the core layer and 2-layer PhC structures in the cladding layer), respectively. Furthermore, by comparing the 7°-titled and 0°-normalized vertical coupling conditions, it can be observed that the purely normalized vertical coupling can collect more output power, resulting in an improved signal-to-noise ratio. This significantly increases the allowable error-free data rate from 85 to 98.9 Gbit/s in the BtB case and from 81.2 Gbit/s to 95.3 Gbit/s in the 100 m OM5-MMF case.
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Kumari, Meet, Vivek Arya, and Hamza Mohammed Ridha Al-Khafaji. "Wheel-Based MDM-PON System Incorporating OCDMA for Secure Network Resiliency." Photonics 10, no. 3 (March 19, 2023): 329. http://dx.doi.org/10.3390/photonics10030329.
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Wheel-based network resilience passive optical network (PON) based on mode division multiplexing (MDM) can be integrated with optical code division multiple access (OCDMA) schemes efficiently for the fixed and backhaul traffic under normal and break/failure fiber operating conditions. In this work, a bidirectional 10/2.5 Gbit/s hybrid MDM-OCDMA-PON system using multi-weight zero cross-correlation (MWZCC) code is proposed. Donut modes 0 and 1 are incorporated by the MDM technique in the proposed system. The benefit of this work is to offer an inexpensive, high-bandwidth and advanced long-haul network with satisfactory resource utilization ability for fiber links with protection against faults and to improve the reliability along with survivability of the network. The simulation results show the successful realization of the multimode fiber (MMF) link at 1.6 km in the uplink and 1.2 km in the downlink directions under an acceptable bit error rate (BER). The minimum accepted received power of −31 dBm in uplink and −27 dBm in downlink over 1 km link at 10/2.5 Gbit/s rate is obtained. Moreover, the minimum received power of −20 dBm in uplink and −30 dBm downlink is achieved by using MWZCC code compared to other codes handling 58 simultaneous end users. Further, the influence of fiber impairments and connected devices on the proposed approach is numerically evaluated. Moreover, it is shown that the wheel based proposed approach performs well than other topologies for the bidirectional network resilience transmission.
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Li, Zequan, Jiantao Liu, Changming Xia, Zhiyun Hou, and Guiyao Zhou. "Supermode Characteristics of Nested Multiple Hollow-Core Anti-Resonant Fibers." Photonics 9, no. 11 (October 29, 2022): 816. http://dx.doi.org/10.3390/photonics9110816.
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Mode-division multiplexing (MDM) can achieve ultra-high data capacity in optical fiber communication. Several impressive works on multicore fiber (MCF), multi-mode fiber, and few-mode multicore fiber have made significant achievements in MDM. However, none of the previous works can simultaneously maintain the transmission loss, chromatic dispersion (CD), and differential group delay (DGD) at a relatively low level. A nested multiple hollow-core anti-resonant fiber (NMH-ARF) has significant potential for applications in MDM. This study proposes a novel NMH-ARF with its structural design based on the traditional single-core nested anti-resonant fiber. We increased the number of nodes between capillaries. By changing the position of the nested tubes, several interconnected areas form when a single core is separated. We investigated the mode-coupling theory and transmission characteristics of this fiber. This fiber structure showed a low sensitivity to bending and achieved a super-low DGD and a super-low confinement loss (CL) at a wavelength of 1.55 µm while keeping CD relatively low.
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Yu, Qixing, Yaoyao Qi, Zhenxu Bai, Jie Ding, Bingzheng Yan, Yulei Wang, Zhiwei Lu, and Dapeng Yan. "L-band of ∼ 1.6 μm tunable multi-wavelength mode-locked Er-doped fiber laser with an MMF- FMF based structure." Optical Fiber Technology 84 (May 2024): 103762. http://dx.doi.org/10.1016/j.yofte.2024.103762.
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Būtaitė, Unė G., Hlib Kupianskyi, Tomáš Čižmár, and David B. Phillips. "How to Build the “Optical Inverse” of a Multimode Fibre." Intelligent Computing 2022 (November 17, 2022): 1–13. http://dx.doi.org/10.34133/2022/9816026.
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When light propagates through multimode optical fibres (MMFs), the spatial information it carries is scrambled. Wavefront shaping reverses this scrambling, typically one spatial mode at a time—enabling deployment of MMFs as ultrathin microendoscopes. Here, we go beyond sequential wavefront shaping by showing how to simultaneously unscramble all spatial modes emerging from an MMF in parallel. We introduce a passive multiple-scattering element—crafted through the process of inverse design—that is complementary to an MMF and undoes its optical effects. This “optical inverter” makes possible single-shot widefield imaging and super-resolution imaging through MMFs. Our design consists of a cascade of diffractive elements, and can be understood from the perspective of both multi-plane light conversion, and as a physically inspired diffractive neural network. This physical architecture outperforms state-of-the-art electronic neural networks tasked with unscrambling light, as it preserves the phase and coherence information of optical signals flowing through it. We show, in numerical simulations, how to efficiently sort and tune the relative phase of up to ~400 step-index fibre modes, reforming incoherent images of scenes at arbitrary distances from the fibre facet. Our optical inverter can dynamically adapt to see through experimentally realistic flexible fibres—made possible by moulding optical memory effects into its design. The scheme is based on current fabrication technology so could be realised in the near future. Beyond imaging, these concepts open up a range of new avenues for optical multiplexing, communications, and computation in the realms of classical and quantum photonics.
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Weng, Yi, Junyi Wang, and Zhongqi Pan. "Recent Advances in DSP Techniques for Mode Division Multiplexing Optical Networks with MIMO Equalization: A Review." Applied Sciences 9, no. 6 (March 20, 2019): 1178. http://dx.doi.org/10.3390/app9061178.
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This paper provides a technical review regarding the latest progress on multi-input multi-output (MIMO) digital signal processing (DSP) equalization techniques for high-capacity fiber-optic communication networks. Space division multiplexing (SDM) technology was initially developed to improve the demanding capacity of optic-interconnect links through mode-division multiplexing (MDM) using few-mode fibers (FMF), or core-multiplexing exploiting multicore fibers (MCF). Primarily, adaptive MIMO filtering techniques were proposed to de-multiplex the signals upon different modes or cores, and to dynamically compensate for the differential mode group delays (DMGD) plus mode-dependent loss (MDL) via DSP. Particularly, the frequency-domain equalization (FDE) techniques suggestively lessen the algorithmic complexity, compared with time-domain equalization (TDE), while holding comparable performance, amongst which the least mean squares (LMS) and recursive least squares (RLS) algorithms are most ubiquitous and, hence, extensively premeditated. In this paper, we not only enclose the state of the art of MIMO equalizers, predominantly focusing on the advantage of implementing the space–time block-coding (STBC)-assisted MIMO technique, but we also cover the performance evaluation for different MIMO-FDE schemes of DMGD and MDL for adaptive coherent receivers. Moreover, the hardware complexity optimization for MIMO-DSP is discussed, and a joint-compensation scheme is deliberated for chromatic dispersion (CD) and DMGD, along with a number of recent experimental demonstrations using MIMO-DSP.
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Noori, Awab, Angela Amphawan, Alaan Ghazi, and S. A. Aljunid Ghazi. "Dynamic evolving neural fuzzy inference system equalization scheme in mode division multiplexer for optical fiber transmission." Bulletin of Electrical Engineering and Informatics 8, no. 1 (March 1, 2019): 127–35. http://dx.doi.org/10.11591/eei.v8i1.1399.
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The performance of optical mode division multiplexer (MDM) is affected by inter-symbol interference (ISI), which arises from higher-order mode coupling and modal dispersion in multimode fiber (MMF). Existing equalization algorithms in MDM can mitigate linear channel impairments, but cannot tackle nonlinear channel impairments accurately. Therefore, mitigating the noise in the received signal of MDM in the presence of ISI to recover the transmitted signal is important issue. This paper aims at controlling the broadening of the signal from MDM and minimizing the undesirable noise among channels. A dynamic evolving neural fuzzy inference system (DENFIS) equalization scheme has been used to achieve this objective. Results illustrate that nonlinear DENFIS equalization scheme can improve the received distorted signal from an MDM with better accuracy than previous linear equalization schemes such as recursive‐least‐square (RLS) algorithm. Desirably, this effect allows faster data transmission rate in MDM. Additionally, the successful offline implementation of DENFIS equalization in MDM encourages future online implementation of DENFIS equalization in embedded optical systems.
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Wei, Yong, Ping Wu, Zongda Zhu, Lu Liu, Chunlan Liu, Jiangxi Hu, Shifa Wang, and Yonghui Zhang. "Surface-Plasmon-Resonance-Based Optical-Fiber Micro-Displacement Sensor with Temperature Compensation." Sensors 18, no. 10 (September 23, 2018): 3210. http://dx.doi.org/10.3390/s18103210.
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Micro-displacement measurements play a crucial role in many industrial applications. Aiming to address the defects of existing optical-fiber displacement sensors, such as low sensitivity and temperature interference, we propose and demonstrate a novel surface plasmon resonance (SPR)-based optical-fiber micro-displacement sensor with temperature compensation. The sensor consists of a displacement-sensing region (DSR) and a temperature-sensing region (TSR). We employed a graded-index multimode fiber (GI-MMF) to fabricate the DSR and a hetero-core structure fiber to fabricate the TSR. For the DSR, we employed a single-mode fiber (SMF) to change the radial position of the incident beam as displacement. The resonance angle in the DSR is highly sensitive to displacement; thus, the resonance wavelength of the DSR shifts. For the TSR, we employed polydimethylsiloxane (PDMS) as a temperature-sensitive medium, whose refractive index is highly sensitive to temperature; thus, the resonance wavelength of the TSR shifts. The displacement and temperature detection ranges are 0–25 μm and 20–60 °C; the displacement and temperature sensitivities of the DSR are 4.24 nm/μm and −0.19 nm/°C, and those of the TSR are 0.46 nm/μm and −2.485 nm/°C, respectively. Finally, by means of a sensing matrix, the temperature compensation was realized.
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Fuentes-Rubio, Yadira Aracely, Yamil Alejandro Zúñiga-Ávalos, José Rafael Guzmán-Sepúlveda, and René Fernando Domínguez-Cruz. "Refractometric Detection of Adulterated Milk Based on Multimode Interference Effects." Foods 11, no. 8 (April 8, 2022): 1075. http://dx.doi.org/10.3390/foods11081075.
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This paper reports on the refractometric detection of water-adulterated milk using an optical fiber sensor whose principle of operation is based on multimode interference (MMI). The device is manufactured in a simple way by splicing a segment of coreless multimode fiber (NC-MMF) between two single-mode fibers (SMFs); neither functionalization nor deposition of a sensing material is required. MMI takes place in the NC-MMF and, when fed with a broadband spectrum, a transmission peak appears at the output of the MMI device due to its inherent filter-like response, whose position depends on the effective refractive index (RI) of the medium surrounding the NC-MMF. Therefore, when the sensor is immersed in different milk–water mixtures, the peak wavelength shifts according to the RI of the mixture. In this way, adulterated milk can be detected from the wavelength shift of the transmission peak. The system was tested with two commercial brands of milk, and adulterations were clearly distinguished in both cases. In the range of interest, from no dilution up to 50% dilution, the sensor exhibits a linear response with a sensitivity of −0.04251 and −0.03291 nm/%, respectively, for the two samples tested. The measurement protocol is repeatable and allows for locating the peak wavelength within <0.34 nm over several repetitions using different samples with the same concentration. A thermal sensitivity of 0.85 nm/°C was obtained, which suggests that the temperature needs to be maintained as fixed during the measurements. The approach presented can be extended to other scenarios as a quality control tool in beverages for human consumption, showing the advantages of simple construction, high sensitivity, and the potential for real-time monitoring.
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Chen, Maoqing, Qifeng Liu, and Yong Zhao. "All Fiber Mach–Zehnder Interferometer Based on Intracavity Micro-Waveguide for a Magnetic Field Sensor." Applied Sciences 11, no. 23 (December 6, 2021): 11569. http://dx.doi.org/10.3390/app112311569.
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A magnetic fluid (MF)-based magnetic field sensor with a filling-splicing fiber structure is proposed. The sensor realizes Mach–Zehnder interference by an optical fiber cascade structure consisting of single mode fiber (SMF), multimode fiber (MMF), and single-hole-dual-core fiber (SHDCF). The core in the cladding and the core in the air hole of SHDCF are used as the reference and sensing light path, respectively, and the air hole of SHDCF is filled with magnetic fluid to realize magnetic field measurement based on magnetic controlled refractive index (RI) characteristics. The theoretical feasibility of the proposed sensing structure is verified by Rsoft simulation, the optimized length of SHDCF is determined by optical fiber light transmission experiment, and the SHDCFs are well fused without collapse through the special parameter setting. The results show that the sensitivity of the sensor is −116.1 pm/Gs under a magnetic field of 0~200 Gs with a good long-term operation stability. The proposed sensor has the advantages of high stability, fast response, simple structure, and low cost, which has development potential in the field of miniaturized magnetic field sensing.
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Khulbe, Manisha, and Harish Parthasarathy. "Orbital Angular Momentum Wave Generation and Multiplexing: Experiments and Analysis Using Classical and Quantum Optics." Wireless Communications and Mobile Computing 2022 (November 11, 2022): 1–24. http://dx.doi.org/10.1155/2022/5355854.
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Optical fiber communication is known as the backbone of communication today for voice, video, and data transmission. Recent advancements in optical technologies are leading us to many new forms of generation of orbital angular momentum (OAM) waves and its transmission technologies. Among them are hypergeometric waveform (HG), Bessel’s waveforms, Laguerre Gaussian waveforms, and other forms of OAMs. This mode of communication is by the twisted form of electromagnetic wave which can accommodate a larger number of channels making communication simpler for wired and wireless communication. In this paper, various methods of OAM waveform generation are presented and are compared in details discussing the various needs in communication. OAM multiplexing is done by spatial division multiplexing (SDM) and wavelength division multiplexing (WDM). Methods of OAM communication, generation techniques, power analysis, and bit error analysis prove efficient transmission capability of OAM waves using low power consumption and low bit error rate in optical communication networks. OAM from fiber can be directly communicated to atmosphere which is found very useful for short distance wireless communication. Experimental validation is discussed for HG, Bessel’s waveforms, and LG waveforms. Pure Optical Vertices (OV) are generated by VCSELs (vertical cavity surface emitting lasers) and transmitted by (MMF) multimode fibers. Various atmospheric effects and challenges are also elaborated in this paper. RSoft OptSim software is used for simulation.
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Liu, Zhaojun, Lianqing Zhu, Lidan Lu, Chunmei Shangguan, Dongliang Zhang, and Jinsong Wang. "Determination of temperature and strain by a compact optical fiber Mach-Zehnder interferometer (MZI) composed of a single-mode fiber (SMF), seven core fiber (SCF), and multimode fiber (MMF) with a fiber Bragg grating (FBG)." Instrumentation Science & Technology 49, no. 4 (March 5, 2021): 457–69. http://dx.doi.org/10.1080/10739149.2021.1884092.
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Ding, Qingan, Li Zheng, Huixin Liu, Junkai Li, Xiaohan Guo, Xudong Cheng, Zhenfei Dai, Qunying Yang, and Jun Li. "Design and Performance Analysis of Hybrid Multidimensional OAM-DM-WDM-OFDM-PON System with High-Capacity and Long-Distance Transmission." Photonics 9, no. 7 (June 27, 2022): 448. http://dx.doi.org/10.3390/photonics9070448.
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Orbital angular momentum (OAM) with mutually orthogonal advantage attribute to break through the high capacity and long-reach transmission limited in the classical passive optical network (PON). Employing Laguerre Gaussian (LG) mode as the orthogonal OAM excitation, a more dimensional multiplexing PON system is proposed to creatively hybridize OAM division multiplexing (OAM-DM) based on wavelength division multiplexing (WDM) and orthogonal frequency division multiplexing (OFDM). By utilizing the compatibility of OAM-DM and WDM, data of 40 Gbit/s OFDM signals is successfully transmitted in 80 km multimode fiber (MMF) with low crosstalk. Within this hybrid system, the effects of different wavelengths and different modes on the bit error rate (BER) are discussed at varying transmission distances. Moreover, the performance of several subsystems carrying quadrature phase-shift keying (QPSK), on-off keying (OOK), and OFDM modulation signals is also compared at a BER less than 3.8×10−3. It is observed that the proposed OAM-DM-WDM-OFDM-PON system has favorable performance, which is a reasonable solution for large-capacity PON architecture.
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Feng, Zhong Yao, Ling Li, Dan Su, and Yu Peng Wang. "A Stable Dual-Wavelengths Fiber Laser Equipped by an In-Fiber Integrated Michelson Interferometer." Applied Mechanics and Materials 421 (September 2013): 122–26. http://dx.doi.org/10.4028/www.scientific.net/amm.421.122.
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In this letter, an in-fiber integrated Michelson interformeteris proposed and experimentally demonstrated. The device consists in the combination of multi-mode fiber (MMF) and a single-mode fiber (SMF) tip which is covered by thick silver film. The MMF excites cladding modes into downstream SMF via the mismatch-core splicing interface. The core-cladding modes are reflected back by the silver and recoupled to fiber core through the MMF. By the reason of fiber-core mismatch and core-cladding modes interference, a well-defined interference pattern is obtained. A stable dual-wavelength fiber laser based on a hybrid gain medium combined with the interferometer filter is realized.
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Ci, Yingjuan, Fang Ren, Xiao Lei, Yidan Li, Deyang Zhou, and Jianping Wang. "A Weakly-Coupled Double Bow-Tie Multi-Ring Elliptical Core Multi-Mode Fiber for Mode Division Multiplexing across C+L+U Band." Applied Sciences 13, no. 10 (May 9, 2023): 5855. http://dx.doi.org/10.3390/app13105855.
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We herein present a weakly-coupled double bow-tie multi-ring elliptical core multi-mode fiber (DBT-MREC-MMF) supporting 22 eigenmodes for mode division multiplexing across the C+L+U band. The proposed fiber introduces a multi-ring elliptical core, bow-tie air holes, and bow-tie stress-applying areas to effectively split adjacent eigenmodes. By utilizing the finite element method (FEM), we accordingly optimized the fiber to support the 22 modes under the weakly-coupled condition. We evaluated the impact of fiber parameters on the minimum effective refractive index difference (min Δneff) between adjacent eigenmodes, model birefringence (Bm), and bending loss at a wavelength of 1550 nm. Additionally, broadband performance metrics, such as effective modal index (neff), effective index difference (Δneff), effective mode area (Aeff), differential mode delay (DMD), and chromatic dispersion (D), were comprehensively studied over the entire C+L+U band, ranging from 1530 to 1675 nm. The proposed fiber is capable of supporting 22 completely separated eigenmodes with a min Δneff between adjacent eigenmodes larger than 3.089 × 10−4 over the entire C+L+U band. The proposed DBT-MREC-MMF holds great potential for use in short-haul communication systems that require MDM to improve transmission capacity and expand bandwidth.
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Skorupski, Krzysztof. "Low-Loss Connection of Hybrid Fibre Optic Systems with Low Sensitivity to Wavelength." Metrology and Measurement Systems 20, no. 4 (December 1, 2013): 697–704. http://dx.doi.org/10.2478/mms-2013-0060.
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Abstract This paper proposes a method for adjusting light waves propagating in systems composed of photonic fibers, light sources and detection elements. The paper presents the properties of these connections in terms of the loss of signal transmission. Different fiber core areas were analyzed, and measurements of the mode-field diameters (MFDs) of selected fiber structures are presented. The study analyzed two types of LMA (Large Mode Area) fiber structures, and the mode-field diameters of these structures were measured on the basis of the radiation distribution obtained under near-field conditions. The results are compared to the values obtained for a SMF-28 single-mode fiber. The LMA structures analyzed in the paper are characterized by low sensitivity of the MFD parameter to the length of transmitted waves, which creates the possibility of their use as intermediate fibers when connecting optical fibers of different diameters. In the wavelength range from 800 nm to 1600 nm, a 3.5% MFD change was observed for the first investigated LMA structure, and a 1% change was observed for the second. In addition, measurements of the mode-field diameters were also made using the transverse offset method for comparison of the results.
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Klimek, Jacek. "Coupled Energy Measurements in Multi-Core Photonic-Crystal Fibers." Metrology and Measurement Systems 20, no. 4 (December 1, 2013): 689–96. http://dx.doi.org/10.2478/mms-2013-0059.
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Abstract This paper outlines a measurement method of properties of microstructured optical fibers that are useful in sensing applications. Experimental studies of produced photonic-crystal fibers allow for a better understanding of the principles of energy coupling in photonic-crystal fibers. For that purpose, fibers with different filling factors and lattice constants were produced. The measurements demonstrated the influence of the fiber geometry on the coupling level of light between the cores. For a distance between the cores of 15 μm, a very low level (below 2%) of energy coupling was obtained. For a distance of 13 μm, the level of energy transfer to neighboring cores on the order of 2-4% was achieved for a filling factor of 0.29. The elimination of the energycoupling phenomenon between the cores was achieved by duplicating the filling factor of the fiber. The coupling level was as high as 22% in the case of fibers with a distance between the cores of 8.5 μm. Our results can be used for microstructured-fiber sensing applications and for transmission-channel switching in liquid-crystal multi-core photonic fibers.
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Feng, Chengcheng, Hao Niu, Hongye Wang, Donghui Wang, Liuxia Wei, Tao Ju, and Libo Yuan. "Probe-Type Multi-Core Fiber Optic Sensor for Simultaneous Measurement of Seawater Salinity, Pressure, and Temperature." Sensors 24, no. 6 (March 8, 2024): 1766. http://dx.doi.org/10.3390/s24061766.
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In this article, we propose and demonstrate a probe-type multi-core fiber (MCF) sensor for the multi-parameter measurement of seawater. The sensor comprises an MCF and two capillary optical fibers (COFs) with distinct inner diameters, in which a 45° symmetric core reflection (SCR) structure and a step-like inner diameter capillary (SIDC) structure filled with polydimethylsiloxane (PDMS) are fabricated at the fiber end. The sensor is equipped with three channels for different measurements. The surface plasmon resonance (SPR) channel (CHSPR) based on the side-polished MCF is utilized for salinity measurement. The fiber end air cavity, forming the Fabry–Pérot interference (FPI) channel (CHFPI), is utilized for pressure and temperature measurement. Additionally, the fiber Bragg grating (FBG) channel (CHFBG), which is inscribed in the central core, serves as temperature compensation for the measurement results. By combining three sensing principles with space division multiplexing (SDM) technology, the sensor overcomes the common challenges faced by multi-parameter sensors, such as channel crosstalk and signal demodulation difficulties. The experimental results indicate that the sensor has sensitivities of 0.36 nm/‰, −10.62 nm/MPa, and −0.19 nm/°C for salinity, pressure, and temperature, respectively. As a highly integrated and easily demodulated probe-type optical fiber sensor, it can serve as a valuable reference for the development of multi-parameter fiber optic sensors.
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Lin, Xiao-Jun, Yu-Xin Gao, Jin-Gan Long, Jia-Wen Wu, Xiang-Yue Li, Wei-Yi Hong, Hu Cui, Zhi-Chao Luo, Wen-Cheng Xu, and Ai-Ping Luo. "Spatial Beam Self-Cleaning in Bi-Tapered Multimode Fibers." Photonics 8, no. 11 (October 27, 2021): 479. http://dx.doi.org/10.3390/photonics8110479.
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We report the spatial beam self-cleaning in bi-tapered conventional multimode fibers (MMFs) with different tapered lengths. Through the introduction of the bi-tapered structure in MMFs, the input beam with poor beam quality from a high-power fiber laser can be converted to a centered, bell-shaped beam in a short length, due to the strengthened nonlinear modes coupling. It is found that the bi-tapered MMF with longer tapered length at the same waist diameter shows better beam self-cleaning effect and larger spectral broadening. The obtained results offer a new method to improve the beam quality of high-power laser at low cost. Furthermore, it may be interesting for manufacturing bi-tapered MMF-based devices to obtain the quasi-fundamental mode beam in spatiotemporal mode-locked fiber lasers.
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Balakin, A. A., S. A. Skobelev, A. V. Andrianov, E. A. Anashkina, and A. G. Litvak. "COHERENT PROPAGATION OF LASER BEAMS IN MCF FIBERS." XXII workshop of the Council of nonlinear dynamics of the Russian Academy of Sciences 47, no. 1 (April 30, 2019): 21–23. http://dx.doi.org/10.29006/1564-2291.jor-2019.47(1).5.
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The successful development of fiber-optic technologies in recent decades has stimulated research on the replacement of components of solid-state laser systems with fiber components, which can drastically change the attractiveness of the corresponding applied developments. Yielding on the energy characteristics of solid-state systems, fiber lasers and nonlinear optical devices have high efficiency of conversion of pump energy to radiation energy associated with waveguide geometry, high quality of the spatial profile of the laser beam, as well as low cost, compactness, lack of alignment in work process. Note that the maximum achievable radiation power in a single fiber is limited primarily by the process of self-focusing, which leads to fiber damage. The use of a multi-core fiber (MCF), consisting of identical equidistant weakly coupled optical fibers, makes it possible to realize initially coherent propagation of laser radiation with a total power noticeably higher than it can be transmitted in a single optical fiber. However, as theoretical and experimental studies have shown, such systems have its own critical power (Balakin et al., 2016) whereby the self-focusing of the quasihomogeneous distribution of the wave field and its separation into a set of incoherent structures occurs. Therefore, we have considered a small-sized optical system of 2N identical weakly coupled optical fibers arranged in a ring (Balakin et. al., 2018). In such systems, it is possible to find stable distributions of intense wave beams, which allow coherent radiation transport over long distances. The total radiation power in the found distributions can significantly (up to 2N times) exceed the critical self-focusing power in continuous media. This manifests itself most clearly for the distribution of un ~ (-1)n with antiphase fields in neighboring waveguides, which is stable at an arbitrary wave beam power. Direct numerical simulation of a nonlinear wave equation confirms the stability of the field distributions found. The research was supported by the RAS Presidium Program «Nonlinear dynamics: fundamental problems and applications».
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Alexeyev, C. N., S. S. Alieva, E. V. Barshak, B. P. Lapin, and M. A. Yavorsky. "Influence of attenuation on the generation of optical vortices in multihelicoidal optical fibers." Journal of Physics: Conference Series 2103, no. 1 (November 1, 2021): 012149. http://dx.doi.org/10.1088/1742-6596/2103/1/012149.
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Abstract In this paper we have studied influence of attenuation on conversion processes of the fundamental mode (FM) in multihelicoidal optical fibers (MHF) in the vicinity of the point of accidental spectrum degeneracy within the framework of the scalar approximation. To this end, we have obtained expressions for modes of the MHF, which consist of the FM and an optical vortex (OV), and shown that conversion of the FM into the OV takes place. The difference in the attenuation coefficients for the partial fields of MHF’s modes leads to deterioration in the conversion process even with an ideal system’s tuning. At sufficiently large values of attenuation coefficients the conversion of the incoming FM into the vortex vanishes. Also we have shown the presence of exceptional point (EP) in the spectra of modes of the MHF and demonstrated enhanced sensitivity of the fiber in the vicinity of the EP to perturbations.
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Fan, Xiaofeng, Shuying Deng, Zhongchao Wei, Faqiang Wang, Chunhua Tan, and Hongyun Meng. "Ammonia Gas Sensor Based on Graphene Oxide-Coated Mach-Zehnder Interferometer with Hybrid Fiber Structure." Sensors 21, no. 11 (June 4, 2021): 3886. http://dx.doi.org/10.3390/s21113886.
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A graphene oxide-coated in-fiber Mach-Zehnder interferometer (MZI) formed with a multimode fiber-thin core fiber-multimode fiber (MMF-TCF-MMF) is proposed and experimentally demonstrated for ammonia gas (NH3) sensing. The MZI structure is composed of two segments of MMF of length 2 mm, with a flame-tapered TCF between them as the sensing arm. The MMFs act as mode couplers to split and recombine light owing to the core diameter mismatch with the other fibers. A tapered TCF is formed by the flame melting taper method, resulting in evanescent wave leakage. A layer of graphene oxide (GO) is applied to the tapered region of the TCF to achieve gas adsorption. The sensor operates on the principle of changing the effective refractive index of the cladding mode of a fiber through changing the conductivity of the GO coating by adsorbed NH3 molecules, which gives rise to a phase shift and shows as the resonant dip shifts in the transmission spectrum. So the concentration of the ammonia gas can be obtained by measuring the dip shift. A wavelength-shift sensitivity of 4.97 pm/ppm with a linear fit coefficient of 98.9% is achieved for ammonia gas concentrations in the range of 0 to 151 ppm. In addition, we performed a repetitive dynamic response test on the sensor by charging/releasing NH3 at concentration of 200 ppm and a relative humidity test in a relative humidity range of 35% to 70%, which demonstrates the reusability and stability of the sensor.
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Bremer, Kort, Lourdes Shanika Malindi Alwis, Yulong Zheng, and Bernhard Wilhelm Roth. "Towards Mode-Multiplexed Fiber Sensors: An Investigation on the Spectral Response of Etched Graded Index OM4 Multi-Mode Fiber with Bragg grating for Refractive Index and Temperature Measurement." Applied Sciences 10, no. 1 (January 2, 2020): 337. http://dx.doi.org/10.3390/app10010337.
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An investigation on the feasibility of utilizing Mode Division Multiplexing (MDM) for simultaneous measurement of Surrounding Refractive Index (SRI) and temperature using a single sensor element based on an etched OM4 Graded Index Multi Mode Fiber (GI-MMF) with an integrated fiber Bragg Grating (BG), is presented. The proposed work is focused on the concept of principle mode groups (PMGs) generated by the OM4 GI-MMF whose response to SRI and temperature would be different and thus discrimination of the said two parameters can be achieved simultaneously via a single sensor element. Results indicate that the response of all PMGs to temperature to be equal, i.e., 11.4 pm/°C, while the response to SRI depends on each PMG. Thus, it is evident that temperature “de-coupled” SRI measurement can be achieved by deducing the temperature effects experienced by the sensor element. Sensitivity of the PMGs to applied SRI varied from 3.04 nm/RIU to of 0.22 nm/RIU from the highest to lowest PMG, respectively. The results verify that it is feasible to obtain dual measurement of SRI and temperature simultaneously using the same, i.e., single, sensing element.
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Zhao, Zhiyong, Yunli Dang, and Ming Tang. "Advances in Multicore Fiber Grating Sensors." Photonics 9, no. 6 (May 26, 2022): 381. http://dx.doi.org/10.3390/photonics9060381.
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In recent years, multicore fiber (MCF) has attracted increasing interest for sensing applications, due to its unique fiber structure of multiple parallel cores in a single fiber cladding, which offers a flexible configurable platform to establish diverse functional fiber devices for sensing applications. So far, a variety of discrete fiber sensors using MCF have been developed, among which one of the major categories is the MCF grating sensors. The most distinct characteristic of MCF that differs from the normal single mode fibers is that the off-center cores of a MCF are sensitive to bending, which is caused by the bending induced tangential strain in off-center waveguides through either compression or stretching. The bending sensitivity has been widely developed for bending/curvature sensing or measuring physical parameters that are associated with bending. In this paper, we review the research progress on MCF-based fiber grating sensors. MCF-based diverse fiber grating sensors will be introduced, whose working principles will be discussed, and various types of applications of the MCF grating sensors will be summarized. Finally, the challenges and prospects of MCF grating for sensing applications will be presented.
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Dong, Xinran, Li Zeng, Dongkai Chu, and Xiaoyan Sun. "Highly Sensitive Dual Parameter Sensor Based on a Hybrid Structure with Multimode Interferometer and Fiber Bragg Grating Fabricated by Femtosecond Laser." Sensors 21, no. 17 (September 3, 2021): 5938. http://dx.doi.org/10.3390/s21175938.
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A hybrid sensing configuration for simultaneous measurement of strain and temperature based on fiber Bragg grating (FBG) written in an offset multimode fiber (MMF) interferometer using femtosecond laser pulse is proposed and demonstrated. A Mach–Zehnder interferometer is formed by splicing a section of MMF between two single-mode fibers (SMFs) and a high interference fringe of up to 15 dB is achieved. The sensing experimental results show a strain sensitivity of −1.17 pm/με and 0.6498 pm/με for the dip of MZI and Bragg peak, while a temperature sensitivity of 42.84 pm/°C and 19.96 pm/°C is measured. Furthermore, the matrix analysis has found that the strain and temperature resolution of the sensor are as high as ±12.36 με and ±0.35 °C, respectively. In addition, the sensor has merits of simple fabrication, good spectral quality, and high resolution, which shows attractive potential applications in dual-parameter sensing.