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- 实验方案
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Bit Error Rate Analysis for Modulating Retro-reflector Free Space Optical Communications with Adaptive Threshold over Correlated Gamma Gamma Fading Channels
摘要： Bit error rate (BER) performance for modulating retro-re?ector (MRR) free space optical communication (FSOC) system with an adaptive threshold over correlated gamma-gamma fading channel is investigated. In order to do this analysis, we ?rst derive two closed form expressions for the probability density function of the correlated MRR channel and our instantaneous BER using the optimal adaptive threshold without channel state information (CSI). Then based on these results, we develop a closed form expression for the average BER in the in?nite series form whose convergence is con?rmed by Cauchy’s ratio test. Simulation results show that we can achieve small SNR penalty of 0.32 dB between our system and the system with CSI by constructing our adaptive threshold using 3 bit pilot data corresponding to a slight throughput reduction.
关键词： Modulating retro-re?ector,Adaptive threshold,Bit error rate performance,Free space optical communication
更新于2025-09-16 10:30:52
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Generalised statistical distribution for turbulence-induced fading in wireless optical communication systems
摘要： The unified M distribution is recently proposed for analysing turbulence-induced fading effects in wireless optical communication (WOC) systems. In developing this model, the large-scale fluctuations have been approximated by gamma distribution, instead of widely accepted log-normal distribution. However, the accuracy of this approximation decreases when the variance of the log-normal distribution is large. As another approach, the inverse-Gaussian (IG) distribution has been proposed in the literature to model the large-scale fluctuation, results in a new accurate, closed-form distribution termed as S model. To generalise the above results, in this study, the authors propose to approximate the large-scale fluctuations by generalised IG distribution. They show that this new approach results in an accurate, closed-form generalised distribution, called here as H model which includes M and S models as its special cases. To show the applicability of the presented model, they consider a WOC system with heterodyne detection scheme and investigate its bit error rate (BER) performance over H-distributed fading channel. They derive closed-form analytical expression for the BER of the considered system and show that in a special case, it coincides with the results presented in the open technical literature.
关键词： bit error rate,M distribution,turbulence-induced fading,wireless optical communication,H model,inverse-Gaussian distribution
更新于2025-09-16 10:30:52
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Fiber Amplifiers and Fiber Lasers Based on Stimulated Raman Scattering: A Review
摘要： Nowadays, in fiber optic communications the growing demand in terms of transmission capacity has been fulfilling the entire spectral band of the erbium‐doped fiber amplifiers (EDFAs). This dramatic increase in bandwidth rules out the use of EDFAs, leaving fiber Raman amplifiers (FRAs) as the key devices for future amplification requirements. On the other hand, in the field of high‐power fiber lasers, a very attractive option is provided by fiber Raman lasers (FRLs), due to their high output power, high efficiency and broad gain bandwidth, covering almost the entire near‐infrared region. This paper reviews the challenges, achievements and perspectives of both fiber Raman amplifier and fiber Raman laser. They are enabling technologies for implementation of high‐capacity optical communication systems and for the realization of high power fiber lasers, respectively.
关键词： stimulated raman scattering,optical communication systems,lasers,fiber optics,amplifiers
更新于2025-09-16 10:30:52
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Ultrahigh Stability 3D TI Bi <sub/>2</sub> Se <sub/>3</sub> /MoO <sub/>3</sub> Thin Film Heterojunction Infrared Photodetector at Optical Communication Waveband
摘要： Infrared (IR) detection at 1300–1650 nm (optical communication waveband) is of great significance due to its wide range of applications in commerce and military. Three dimensional (3D) topological insulator (TI) Bi2Se3 is considered a promising candidate toward high-performance IR applications. Nevertheless, the IR devices based on Bi2Se3 thin films are rarely reported. Here, a 3D TI Bi2Se3/MoO3 thin film heterojunction photodetector is shown that possesses ultrahigh responsivity (Ri), external quantum efficiency (EQE), and detectivity (D*) in the broadband spectrum (405–1550 nm). The highest on–off ratio of the optimized device can reach up to 5.32 × 104. Ri, D*, and the EQE can reach 1.6 × 104 A W?1, 5.79 × 1011 cm2 Hz1/2 W?1, and 4.9 × 104% (@ 405 nm), respectively. Surprisingly, the Ri can achieve 2.61 × 103 A W?1 at an optical communication wavelength (@ 1310 nm) with a fast response time (63 μs), which is two orders of magnitude faster than that of other TIs-based devices. In addition, the device demonstrates brilliant long-term (>100 days) environmental stability under environmental conditions without any protective measures. Excellent device photoelectric properties illustrate that the 3D TI/inorganic heterojunction is an appropriate way for manufacturing high-performance photodetectors in the optical communication, military, and imaging fields.
关键词： photodetectors,Bi2Se3 thin films,infrared optical communication wavebands,heterojunction structures,ultrafast response times
更新于2025-09-16 10:30:52
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166 Gbps data rate for underwater wireless optical transmission with single laser diode achieved with discrete multi-tone and post nonlinear equalization
摘要： In this paper, we experimentally demonstrate a 450-nm laser underwater wireless optical transmission system by using adaptive bit-power loading discrete multi-tone (DMT) and Volterra series based post nonlinear equalization. Post nonlinear equalization mitigates the nonlinear impairment of the UWOC system. By incorporating post nonlinear equalization with a 3rd-order diagonal plane kernel, the received signal-to-noise ratio (SNR) can be improved by ~2 dB compared with a linear equalization method. The measured transmission capacity of the UWOC system is 16.6 Gbps over 5 m, 13.2 Gbps over 35 m, and 6.6 Gbps over 55 m tap water channel, with bit error rates (BERs) below the standard hard-decision forward error correction (HD-FEC) limit of 3.8 × 10?3. The used electrical signal bandwidth is 2.75 GHz, corresponding to electrical spectrum efficiency of ～6 bit/s/Hz. The distance-datarate product reaches 462 Gbps*m at 35 m tap water transmission. To the best of our knowledge, both the data rate and distance-data rate product are the largest reported for single laser diode.
关键词： Volterra series,discrete multi-tone,underwater wireless optical communication,high-speed transmission,post nonlinear equalization
更新于2025-09-16 10:30:52
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Transmit laser selection for two hop decode and forward FSO communication with pointing errors
摘要： In this letter, two systems have been proposed for efficient unidirectional free space optical (FSO) cooperative communication-one with only transmit laser selection (TLS) and the other using optical spatial modulation (OSM) along with TLS. Performance analysis of such systems for Gamma-Gamma (G-G) fading channels both with and without Pointing errors have been carried out in terms of outage probability and average symbol error probability (ASEP). Our proposed TLS system over G-G channel (with pointing error) yields a signal to noise ratio (SNR) gain of at least 10 dBm over the conventional FSO system.
关键词： cooperative communication,Free space optical communication,transmit laser selection,pointing errors,Gamma-Gamma fading,optical spatial modulation
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM) - Hong Kong, China (2019.7.8-2019.7.12)] 2019 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM) - Closed loop controlled optical tracking module for free-space optical communications
摘要： In this paper, a closed loop controlled optical tracking module for free-space optical communication is presented. The motion of the optical tracking module is achieved using a pan-tilt mechanical platform driven by two servomotors. The optical tracking module consists of optical elements including beam splitters and quadrant photodiodes to extract the angular parameters of the incident wave. Optical as well as dynamic modeling is performed to confirm the tracking functionality of the system. Furthermore, to validate the concept, experimentation has been carried out by placing a laser emission module in front of a fixed optical tracking module. The laser was moved in free-space with the help of a mechanical structure and the successful tracking of the optical tracking module has been observed.
关键词： pan-tilt mechanical platform,servomotors,quadrant photodiodes,beam splitters,optical tracking module,free-space optical communication
更新于2025-09-12 10:27:22
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Carrier Frequency Offset Estimation for BPSK Signals in Coherent Optical Communications
摘要： In this paper, a algorithm which is used for carrier frequency offset (CFO) estimation is proposed in coherent optical communications system with binary phase-shift keying (BPSK) modulation. The proposed algorithm utilizes the frequency divider to broaden the range of the estimation algorithm. In a 5-GBaud coherent BPSK system, simulation results show that when 12dB signal-to-noise ratio (SNR) and 512 samples are utilized, a 8 frequency divider can expand the range of the frequency offset estimation from [-0.5GHz, +0.5GHz] to [-4GHz, +4GHz] and the CFO estimation error can be obtained less than 5MHz. The paper presents a novel algorithm that features the large estimation range for carrier frequency offset while estimation error is not enlarged. The experimental results verified the effectiveness of the proposed algorithm.
关键词： costas optical phase-locked loop,BPSK modulation,carrier frequency offset estimation,frequency divider,Coherent optical communication
更新于2025-09-12 10:27:22
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ALL-OPTICAL LOGIC GATES BASED ON SPATIAL-SOLITON INTERACTIONS IN OPTICAL COMMUNICATION SPECTRAL REGION
摘要： New designs of all-optical logic gates based on spatial-soliton interactions in optical communication spectral regions were proposed. The proposed structures are composed of local nonlinear Mach-Zehnder interferometer (MZI) waveguide structures with multi-input ports and two nonlinear output ports. They can be used to design various all-optical logic gates. The nonlinear MZI waveguide structure with local nonlinear waveguides functions like a phase shifter. It employs angular de?ection of spatial solitons controlled by the phase modulation created in the local nonlinear MZI. The light-induced index changes in the local nonlinear MZI waveguide structures break the symmetry of structure and make the output signal beam propagate through di?erent nonlinear output waveguides. By properly choosing the input control power, the spatial solitons will be switched to di?erent output ports. The numerical results show that the proposed local nonlinear MZI waveguide structures could really function as all-optical logic gates in the optical communication spectral region.
关键词： all-optical logic gates,spatial-soliton interactions,nonlinear waveguides,optical communication spectral regions,Mach-Zehnder interferometer
更新于2025-09-12 10:27:22
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Modified downhill simplex method for fast adaption of optical filters in optical communication systems
摘要： The authors propose a control method based on the downhill simplex (Nelder–Mead) method for adaptive optical ?lters used for channel equalisation in optical communication systems. The performance of this method is compared to gradient methods in numerical simulations. The results show that the proposed method can adapt the ?lter to more rapid changes of the transmission channel than the gradient methods.
关键词： adaptive optical filters,channel equalisation,downhill simplex method,optical communication systems,Nelder–Mead method
更新于2025-09-12 10:27:22