- 标题
- 摘要
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- 实验方案
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Transient and Steady-State Radiation Response of Phosphosilicate Optical Fibers: Influence of H2 Loading
摘要： The radiation response of a phosphorus-doped multimode optical fiber is investigated under both transient (pulsed X-rays) and steady state (γ-rays and X-rays) irradiations. The influence of a H2 pre-loading on the fiber radiation induced attenuation (RIA) in the 300 nm - 2000 nm wavelength range has been characterized. To better understand the impact of this treatment, online behaviors of fiber samples containing different amounts of gas are compared from glass saturation (100%) to less than 1%. In addition to these in situ experiments, additional post-irradiation spectroscopic techniques have been performed such as electron paramagnetic resonance or luminescence measurements to identify the different point defects responsible for the induced losses and their H2 dependence. All our data at room temperature (RT) highlight a strong positive impact of H2, even at very low concentrations, on the RIA. Hydrogen quickly passivates (t<1 s) most of the defects responsible for the visible – near-IR RIA, mainly phosphorus oxygen hole centers (POHC) and P1 defects. However, one year after the H2-loading at RT or when operating at liquid nitrogen temperature, the RIA levels of the not-treated and H2-loaded fiber become comparable. The obtained results provide a better understanding of the potential and limitations of H2-loading treatment to design radiation hardened fiber links.
关键词： temperature,point defects,phosphorus,H2-loading,X-rays,radiation effects,optical fibers,pulsed X-rays
更新于2025-09-19 17:13:59
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Graded‐Index Ytterbium‐Doped Optical Fiber Fabricated through Vapor Phase Chelate Delivery Technique
摘要： Herein, the fabrication of ytterbium-doped graded refractive-index few-mode fiber (GRIN-FMF) is described for the first time following a vapor phase chelate delivery technique. Investigation is carried out to find out the best possible approach to fabricate the preform. The optimization of the process steps along with composition and associated process parameters leads to a parabolic refractive-index profile with a profile parameter of 2 in the developed fiber. A large core of 30 μm diameter and a low numerical aperture (NA) of 0.08 with graded distribution of dopant ions is achieved with a good repeatability. Amplification gain of more than 20 dB with good beam quality for pulses with kW peak power without any distortion in temporal, spectral, and spatial profile proves the potential of the fiber for many promising applications.
关键词： preform fabrication,graded-index fibers,ytterbium,vapor phase chelate delivery,fiber lasers
更新于2025-09-19 17:13:59
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[OSA Optical Fiber Sensors - Lausanne (2018..-..)] 26th International Conference on Optical Fiber Sensors - Label-free distributed hydrogen sensing with stimulated Raman scattering in hollow-core fibers
摘要： We present the first experimental demonstration of distributed hydrogen sensing using stimulated Raman scattering in gas-filled hollow-core photonic crystal fibers. The system performances in terms of sensitivity, selectivity, dynamic range and sensing distance are discussed.
关键词： Fiber optics,Spectroscopy,Fiber optics sensors,Spectroscopy, Raman,Photonic crystal fibers
更新于2025-09-19 17:13:59
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Thermal Poling of Optical Fibers: A Numerical History
摘要： This review gives a perspective of the thermal poling technique throughout its chronological evolution, starting in the early 1990s when the first observation of the permanent creation of a second order non-linearity inside a bulk piece of glass was reported. We then discuss a number of significant developments in this field, focusing particular attention on working principles, numerical analysis and theoretical advances in thermal poling of optical fibers, and conclude with the most recent studies and publications by the authors. Our latest works show how in principle, optical fibers of any geometry (conventional step-index, solid core microstructured, etc) and of any length can be poled, thus creating an advanced technological platform for the realization of all-fiber quadratic non-linear photonics.
关键词： thermal poling,numerical analysis,non-linear photonics,optical fibers
更新于2025-09-19 17:13:59
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[IEEE 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Bengaluru, India (2018.12.17-2018.12.19)] 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Simultaneous generation of laser sources in S, C and L bands through four-wave mixing of electro-optic frequency combs
摘要： Increasing bandwidth demands necessitate the use of several carriers in wavelength division multiplexing. Conventionally, carrier wavelengths were generated by individual lasers which suffer from large area and power requirements with scaling of number of carriers. We demonstrate simultaneous generation of over 316 wavelengths in S, C and L bands from two lasers spaced 4 nm apart in the C-band. Electro-optic modulators initially scale each laser to 9 lines (in 20 dB bandwidth). The electro-optic frequency combs are power scaled to ~800 mW and undergo cascaded four-wave mixing in highly nonlinear fiber to generate wavelengths in the three bands. The number of lines in 20 dB bandwidth in S, C and L bands are 88, 160 and 68 respectively. This system can also be used for RF arbitrary waveform generation.
关键词： four-wave mixing,electro-optic modulators,wavelength division multiplexing,highly nonlinear fibers
更新于2025-09-19 17:13:59
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Structural and mechanical characterization of carbon fibers grown by laser induced chemical vapor deposition at hyperbaric pressures
摘要： Laser induced chemical vapor deposition (LCVD) of freestanding carbon fibers from ethylene at hyperbaric pressures was investigated. Relationships between processing conditions, growth behavior, microstructure, and mechanical properties of the carbon fibers were established. It is found that the fiber growth rates are limited by surface reaction kinetics at low temperatures and limited by gas phase nucleation at high temperatures. At higher pressures and intermediate temperatures, growth becomes mass transport limited whereupon the fibers exhibit drastic changes in morphology and microstructure from a core-shell, smooth appearance to nodular formations. The tensile strengths of the carbon fibers grown by LCVD are generally poor due to the nature of graphitic carbon deposits. However, the Weibull modulus among the LCVD grown carbon fibers was found to be very high. Effects of processing conditions and microstructure on the fiber strengths are observed and discussed.
关键词： Microstructure,Hyperbaric pressures,Laser induced chemical vapor deposition,Carbon fibers,Mechanical properties
更新于2025-09-19 17:13:59
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Structural and spectroscopic studies on the concentration dependent erbium doped lithium bismuth boro tellurite glasses for optical fiber applications
摘要： High gain and better optical properties are the key requirement for the optical fibers and amplifiers to meet the current technological demand. In this regard, in the present investigation, erbium doped lithium bismuth boro tellurite glasses are prepared using melt-quenching technique. The prepared glasses were extensively characterized through, XRD, DSC, UV–Vis-NIR and also Luminescence and Decay techniques to study the concentration dependent structural, optical and luminescence properties. Prepared glasses are amorphous in nature and the corresponding band gap energy decreases with erbium concentration indicates increase of metallicity of the glasses. FTIR studies show different vibration modes majorly borate groups. In addition, Judd-Oflet theory is employed to derive different optical parameters such as intensity parameters, oscillatory strength, branching ratio, stimulated emission cross section and time decay to validate the experimental results of prepared glasses towards optical fiber applications. Estimated values of Stimulated emission, effective band width and gain band width values found higher when compared with other host glasses. Results also show that, 100% branching ratio is obtained for the highest intense peaks corresponds to the transition 4I13/2 → 4I15/2 in NIR luminescence spectra for 1.53 μm broad band. For power dependent 980 nm excitation, up-conversion spectra shows two transitions, namely 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 at 541 and 655 nm corresponds to green and red emission respectively. From the McCumber’s theory, the absorption and emission cross section more comaprable values are obtained for 1 mol% erbium doped glass. About 40% population inversion is obtained with C band from 1500 to 1550 nm. The results suggests that, the prepated glasses are the potential candidates for optical fiber applications.
关键词： Band gap energy,Judd-Oflet,NIR emission,Optical fibers,Boro-tellurite glasses
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE International Conference on Space Optical Systems and Applications (ICSOS) - Portland, OR, USA (2019.10.14-2019.10.16)] 2019 IEEE International Conference on Space Optical Systems and Applications (ICSOS) - Real Time Photon-Counting Receiver for High Photon Efficiency Optical Communications
摘要： We present a scalable design for a photon-counting ground receiver based on superconducting nanowire single photon detectors (SNSPDs) and field programmable gate array (FPGA) real-time processing for applications to space-to-ground photon starved links, such as the Orion EM-2 Optical Communication Demonstration (O2O) [1], and future deep space or low transmitter power missions. The receiver is designed to receive a serially concatenated pulse position modulation (SCPPM) waveform [2], which follows the Consultative Committee for Space Data Systems (CCSDS) Optical Communications Coding and Synchronization Red Book standard [3]. The receiver design uses multiple individually fiber coupled, 80% detection efficiency commercial SNSPDs in parallel to scale to a required data rate, and is capable of achieving data rates up to 528 Mbps. For efficient fiber coupling from the telescope to the array of parallel detectors that can be scaled both to telescope aperture size and the number of detectors, we use either a single mode fiber (SMF) photonic lantern or a few-mode fiber (FMF) photonic lantern [4]. In this paper we give an overview of the receiver system design, the characteristics of the photonic lanterns, the performance of the SNSPDs, and system level tests. We show that 40 Mbps can be received using a single SNSPD, and discuss aspects for scaling to higher data rates.
关键词： few-mode fibers,superconducting nanowire,optical communications,single photon detectors
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Resonance Energy Leakage in Hollow Core Fiber for Sensitive Liquid Level Measurement
摘要： A sensitive liquid-level sensor based on energy leakage of anti-resonant reflecting guidance in a hollow core fiber is proposed and experimentally demonstrated. It is constructed by splicing a 15mm-long hollow core fiber with a cladding thickness of 40 μm to single mode fibers. Since the leakage of resonance energy is sensitive to surrounding liquids, liquid level is measured by pushing the sensor transversely against the liquid surface to efficiently change the proportion of fiber circumference in liquid. Based on the variation of transmission power at resonant wavelengths, liquid-level measurement was achieved with sensitivity up to 7.64 dB/mm, which is several times higher than that of normal sensors immersed vertically into the liquid.
关键词： Hollow core fibers,Anti-resonant reflecting guidance,Liquid level sensors
更新于2025-09-16 10:30:52
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Multicore-fiber solitons and laser-pulse self-compression at light-bullet excitation in the central core of multicore fibers
摘要： The propagation of laser pulses in multicore fibers (MCFs) made of a central core and an even number of cores located in a ring around it is studied. Approximate quasisoliton homogeneous solutions of the wave field in the MCF considered are found. The stability of the in-phase soliton distribution is shown analytically and numerically. At low energies, its wave field is distributed over all MCF cores and has a duration that exceeds the duration of the nonlinear Schr?dinger equation (NSE) soliton with the same energy by many (i.e., five to six) times. In contrast, almost all of the radiation at high energies is concentrated in the central core with a duration similar to the NSE soliton. The transition between the two types of distributions is very sharp and occurs at a critical energy, which is weakly dependent on the number of cores and on the coupling coefficient with the central core. The self-compression mechanism of laser pulses was proposed. It consists in injecting such MCFs with a wave packet being similar to the found soliton and having an energy larger than the critical value. It is shown that the compression ratio depends weakly on the energy and the number of cores and is approximately equal to six times with an energy efficiency of almost 100%. The use of longer laser pulses allows one to increase the compression ratio up to 30–40 times with an energy efficiency of more than 50%. The obtained analytical estimates of the compression ratio and its efficiency are in good agreement with the results of a numerical simulation.
关键词： light-bullet excitation,laser-pulse self-compression,nonlinear Schr?dinger equation,multicore fibers,solitons
更新于2025-09-16 10:30:52