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Long tapered fiber with array of FBG
摘要： A tapered optical fiber with an adiabatic transition from single-mode to a few-mode part has been fabricated with an array of fiber Bragg gratings being inscribed during the drawing process. We demonstrate that the propagating optical signal remains single-mode along the tapered fiber FBG array even in a multimode part of it. The spectral width of the reflected signal from the tapered optical fiber is 4 nm. The level of the reflected signal is up to 5% at some wavelengths.
关键词： Tapered optical fibers,Fiber optics sensors,Fiber Bragg gratings
更新于2025-11-28 14:23:57
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Optical Characterization of Doped Thermoplastic and Thermosetting Polymer-Optical-Fibers
摘要： The emission properties of a graded-index thermoplastic polymer optical fiber and a step-index thermosetting one, both doped with rhodamine 6G, have been studied. The work includes a detailed analysis of the amplified spontaneous emission together with a study of the optical gains and losses of the fibers. The photostability of the emission of both types of fibers has also been investigated. Comparisons between the results of both doped polymer optical fibers are presented and discussed.
关键词： polymer optical fibers,thermoplastic fibers,rhodamine 6G,light-emitting polymers,optical gain,amplified spontaneous emission,thermosetting fibers
更新于2025-11-14 15:30:11
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Approaching Terabits per Carrier Metro-Regional Transmission Using Beyond-100GBd Coherent Optics with Propabilistically Shaped DP-64QAM Modulation
摘要： This research work proposed and experimentally demonstrated beyond-100GBd probabilistically-shaped coherent optics that support transmission of ~1.2 Tbps coded line rate and ~0.9 Tbps net bit rate per optical carrier over metro-regional distances. Pursuing next-generation transmission systems having both high capacity approaching Terabits per wavelength and high spectral efficiency requires engineering efforts from different aspects, which may includes the enhancement of analog-to-digital or digital-to-analog (AD/DA) interfaces, the improvement of channel characteristics, and also the realization of better receiver sensitivities, preferably through DSP techniques such as probabilistic shaping (PS). By doing so, this work achieved single-channel and 112.5GHz-WDM transmission of 900G wavelengths over 800 km and 400 km, respectively, which employed PS DP-64QAM modulation format at 105 GBd, yielding a net spectral efficiency of 8.05 bits/s/Hz. Such a high symbol rate was demonstrated using a commercially available DAC unit without band-interleaving. The enhanced optical channel consists of ITU-T G.654 compliant Terawave SLA+ fiber spans with backward-pumped Raman amplifiers. In addition, with the same PS DP-64QAM modulation format and the same enhanced channel, this research work also demonstrated that 400G wavelengths can be delivered over 2,800 km supporting long-haul applications.
关键词： quadrature amplitude modulation,probabilistic shaping,optical fibers,Coherent optical communications
更新于2025-09-23 15:23:52
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Contrast of optical activity and rogue wave propagation in chiral materials
摘要： We report the contrast of optical activity and properties of nonparaxial optical rogue waves for the higher-order nonparaxial chiral nonlinear Schr?dinger (NLS) equation. The latter describes the propagation of ultrashort optical pulses in chiral optical fibers. Both first- and second-order rogue wave solutions are investigated analytically by the modified Darboux transformation (MDT) and numerically by one pseudo-spectral method. The interplay of chiral materials on rogue wave propagation is elucidated, and the results can be applied on optical communication and in others physical systems.
关键词： Chirality and optical activity,Chiral optical fibers,Rogue wave propagation,Chiral materials
更新于2025-09-23 15:23:52
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FPGA-Based Implementation of an Artificial Neural Network for Measurement Acceleration in BOTDA Sensors
摘要： In recent years, using distributed fiber-optic sensors based on Brillouin scattering, for monitoring pipelines, tunnels, and other constructional structures have gained huge popularity. However, these sensors have a low signal-to-noise ratio (SNR), which usually increases their measurement error. To alleviate this issue, ensemble averaging is used which improves the SNR but in return increases the measurement time. Reducing the noise by averaging requires hundreds or thousands of scans of the optical fiber; hence averaging is usually responsible for a large percent of the entire system latency. In this paper, we propose a novel method based on artificial neural network for SNR enhancement and measurement acceleration in distributed fiber-optic sensors based on the Brillouin scattering. Our method takes the noisy Brillouin spectrums and improves their SNR by 20 dB, which reduces the measurement time significantly. It also improves the accuracy of the Brillouin frequency shift estimation process and its latency by more than 50% in comparison with the state-of-the-art software and hardware solutions.
关键词： Artificial neural network (ANN),digital signal processing,optical fibers,curve fitting,field-programmable gate arrays (FPGAs)
更新于2025-09-23 15:23:52
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Tapered Fibers Combined With a Multi-Electrode Array for Optogenetics in Mouse Medial Prefrontal Cortex
摘要： Optogenetics offers many advantages in terms of cell-type specificity, allowing to investigate functional connectivity between different brain areas at high spatial and neural population selectivity. In order to obtain simultaneous optical control and electrical readout of neural activity, devices called “optrodes” are employed. They are typically composed of a linear array of microelectrodes integrated on a slender probe shafts combined with flat-cleaved optical fibers (FF) placed above the recording sites. However, due to tissue absorption and scattering, light delivered by the FF unevenly illuminates the region of interest. This issue is of particular relevance when cellular populations are disposed along the dorso-ventral axis, such as in medial prefrontal cortex (mPFC) where cortical layers are aligned vertically. The study presented here aims at using tapered optical fibers (TFs) in combination with a 16-electrode neural probe to better access neural populations distributed along the dorso-ventral axis in the mPFC of newborn mice, restricting light delivery over a specific portion of the cortical layer of interest. Half of the TF surface is coated with a reflecting metal blocking the light to enable light delivery from one side of the probe’s shaft only, with the probe base being designed to host the fiber without interfering with the wire-bonds that connect the recording sites to a printed circuit board. Monte-Carlo simulations have been implemented to define the relative TF-probe position and to identify the light intensity distribution above the recording sites. In vivo recordings indicate that simultaneous optical stimulation and electrical readout of neural activity in the mPFC benefit from the use of the engineered TF-based optrode in terms of a more uniform light distribution along the dorso-ventral axis and the possibility of restricting light delivery to a subset of electrical recording sites of interest.
关键词： optogenetics,medial prefrontal cortex,tapered fibers,optrode,optical fibers
更新于2025-09-23 15:22:29
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Single-mode large-mode-area Er–Yb fibers with core based on phosphorosilicate glass highly doped with fluorine
摘要： Single-mode Er–Yb fibers with the core based on a phosphorosilicate glass matrix (up to 6.5 mol.% P2O5) highly doped with fluorine (up to 0.9 wt.%) were fabricated using an all-gas-phase modified chemical vapor deposition method. The core numerical aperture was in the range of 0.07–0.08 relative to the pure silica, which allowed us to increase the single-mode core diameter up to 20 μm. The slope efficiency in lasers based on the fabricated fibers reached 34% relative to the launched pump power.
关键词： fiber lasers,optical fibers,erbium–ytterbium fibers,erbium-doped fiber amplifiers
更新于2025-09-23 15:22:29
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Bidirectional SMF and PF-POF transmission of 400 Gbps Nyquist shaped on DP-QPSK systems
摘要： This work experimentally shows a transmission path based on standard single-mode optical fiber and perfluorinated graded-index plastic optical fiber with the connections between distinct optical fibers being made by fiber collimators using free-space optical transmission. The data stream consists of a bidirectional 400 Gbps optical transmission using four wavelength channels with quadrature phase-shift keying modulation format, combined with dual-polarization and Nyquist pulse-shaped. The results obtained seeks to study the use of short-distance cables in plastic optical fiber as a flexible means of interconnection, when inserted between single-mode optical fibers or as a coupling medium between devices with single-mode optical inputs/outputs located in data centers/video headends.
关键词： bidirectional transmission,optical network convergence,free-space optical connection,Perfluorinated polymer optical fibers
更新于2025-09-23 15:21:21
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Distributed Measurement of Polarization Mode Coupling in Polarization Maintaining Fibers Using Microwave Photonic Filter Technique
摘要： Polarization mode coupling (PMC) is a detrimental effect that limits the polarization maintaining performance of polarization maintaining fibers (PMF). In this paper, we propose and demonstrate a novel method based on a principle similar to that of a microwave photonic filter (MPF) for the PMC distribution measurement. By regarding the PMF with PMC taking place as an MPF and measuring its transfer function in frequency domain, we are able to identify the intensities and locations of PMC events along PMFs. After detailed theoretical analysis and numerical simulations, validation experiments have been conducted on four PMF segments with rotational splicing between each other to manually generate PMCs. The measurement results of PMC positions and strengths are in accordance with the preset values. With a frequency scanning step of 16 MHz and a range of 14.4 GHz, such method can achieve a spatial resolution of 30 m and a measurement range of 27 km. The proposed method is suitable for the measurement of PMCs along PMFs up to tens of kilometers.
关键词： microwave filters,optical fibers,microwave photonics,Optical fiber polarization
更新于2025-09-23 15:21:21
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Optical Gaussons for nonlinear logarithmic Schr?dinger equations via the variational iteration method
摘要： In this work, we study the logarithmic Schr?dinger equation, with and without a detuning term. We derive optical Gaussons, named for their Gaussian shape, for these logarithmic models via using the variational iteration method. The obtained Gaussons are characterized by no soliton radiation, and propagate through dispersion-managed optical fibers. The physical structures of the derived Gaussons, namely, its amplitude and width will be examined for a variety numerical values of the parameters.
关键词： Schr?dinger equation,Logarithmic nonlinearity,Optical fibers,Gaussons
更新于2025-09-23 15:21:21