1 西安邮电大学电子工程学院,陕西 西安 710121
2 西安精密机械研究所,陕西 西安 710077
为了研究粗糙动态海平面对折射偏振光的影响,利用Elfouhaily海浪谱和快速傅里叶变换生成随机动态海面,建立了激光跨粗糙空气-海水界面的偏振光传输模型。研究了不同风速、不同距离、不同光发散角下激光穿过空气-海水信道后的偏振特性和闪烁指数。仿真结果表明,风速越大,接收偏振度越小,相同条件下,圆偏振光偏振度远大于线偏振光;信道距离越长,偏振度越低;风速和链路距离变大时,闪烁指数也变大;当光束发散角减小时,闪烁指数变大;反之闪烁指数减小。验证了所提模型的可行性。本文研究为空气-海水光通信提供了理论依据。
水下无线光通信 Elfouhaily谱 跨介质 偏振光 闪烁指数
Author Affiliations
Abstract
School of Information and Communication Engineering, Dalian University of Technology, Dalian 116024, China
In order to alleviate the impact of turbulence on the performance of underwater wireless optical communication (UWOC) in real time, and achieve high-speed real-time transmission and low cost and miniaturization of equipment, a real-time multiple-input and multiple-output (MIMO) high-speed miniaturized UWOC system based on a field-programmable gate array (FPGA) and a high-power light-emitting diode (LED) array is designed in this Letter. In terms of multiplexing gain, the imaging MIMO spatial multiplexing and high-order modulation for the first time are combined and the real-time high-speed transmission of PAM-4 signal based on the LED array light source in 12 m underwater channel at 100 Mbps rate is implemented, which effectively improves the throughput of the UWOC system with a high-power commercial LED light source. In light of diversity gain, the system employs the diversity of repeated coding scheme to receive two identical non-return-to-zero on-off keying (NRZ-OOK) signals, which can compensate the fading or flickering sublinks in real time under the bubble-like simulated turbulence condition, and has high robustness. To our knowledge, this is the first instance of a high rate and long-distance implementation of a turbulence-resistant real-time MIMO miniaturized UWOC system based on FPGA and high-power LED arrays. With spatial diversity or spatial multiplexing capabilities, its low cost, integrity, and high robustness provide the system with important practical prospects.
underwater wireless optical communication MIMO spatial diversity spatial multiplexing Chinese Optics Letters
2024, 22(2): 020601
大连理工大学信息与通信工程学院,辽宁 大连 116024
针对水下无线通信高速率、远距离、低成本和小型化设备的实用需求,本文设计研制了一种高鲁棒性的基于现场可编程门阵列(FPGA)和大功率LED阵列的小型化水下无线光通信系统。其光发射机的光源采用45 W大功率LED阵列,基于FPGA实现高阶调制与编码,并设计了准直光学发射天线有效减少光束发散角,大幅度延长了传输距离。在光接收端,设计了一种基于3 mm大孔径雪崩光电二极管(APD)的自动增益控制放大和FPGA解调与信号处理的光接收机,降低了光通信系统对准的严苛要求。该系统可实现30 Mbps 开关键控(OOK)信号和正交幅度调制(QAM)信号(16QAM信号)的12 m水下信道实时传输,二者的误码率(BER)分别为2.467×10-4和3.467×10-3。此外,该系统还实现了22 Mbps的非归零(NRZ)-OOK整形信号12 m水下+30 m空气的跨介质传输(总长度为42 m),BER为3.619×10-4。最后,实现了12 m水下信道中接收机偏离主光轴40°之内22 Mbps OOK信号的有效接收,提高了系统的鲁棒性。
水下无线光通信 现场可编程门阵列 LED阵列 高阶调制 小型化光端机
红外与激光工程
2023, 52(9): 20220814
中国海洋大学物理与光电工程学院,山东 青岛 266100
通过涡旋光束的轨道角动量的叠加态的识别研究,提出了一种在水下无线光通信中运用涡旋光束进行高维信息调制与解调的方法。给出了两种涡旋光束的叠加态的识别方法和流程,并对水信道传输后的叠加态的光强分布图进行了识别,得出叠加态中的拓扑荷数,以此通过实验论证了轨道角动量叠加态可在低拓扑荷数情况下实现16维信息的调制与解调,为涡旋光束在水下无线光通信中的应用提供了一种可行方案。
大气光学与海洋光学 水下无线光通信 涡旋光束 轨道角动量 空间光调制器 图像识别 激光与光电子学进展
2023, 60(9): 0901001
Author Affiliations
Abstract
1 Optical Communications Laboratory, Ocean College, Zhejiang University, Zhoushan 316021, China
2 Hainan Institute of Zhejiang University, Sanya 572025, China
3 Key Laboratory of Ocean Observation-Imaging Testbed of Zhejiang Province, Ocean College, Zhejiang University, Zhoushan 316021, China
In this paper, an optical pulse amplitude modulation with 4 levels (PAM-4) using a fiber combiner is proposed to enhance the data rate of a field-programmable gate-array-based long-distance real-time underwater wireless optical communication system. Two on–off keying signals with different amplitudes are used to modulate two pigtailed laser diodes, respectively, and the generated optical signals are superimposed into optical PAM-4 signals by a fiber combiner. The optical PAM-4 scheme can effectively alleviate the nonlinearity, although it reduces the peak-to-peak value of the emitting optical power by 25%. A real-time data rate of 187.5 Mbit/s is achieved by using the optical PAM-4 with a transmission distance of 50 m. The data rate is increased by about 25% compared with the conventional electrical PAM-4 in the same condition.
underwater wireless optical communication FPGA PAM-4 Chinese Optics Letters
2023, 21(2): 020601
西安邮电大学 电子工程学院,陕西 西安 710121
海水信道对光的吸收和散射造成信号衰减,海水湍流造成信号幅度起伏变化,两者都会降低水下无线光通信(UWOC)系统误码率(BER)性能。将两个信道特性对信号性能的影响综合考虑,提出了一种将传输距离和湍流概率密度函数等效为系统信噪比(SNR)和湍流噪声的方法,然后将信号衰减和湍流噪声同时作用在信号波形中,建立水下复合信道信号传输模型。依据实验系统参数,模拟复合信道下高斯最小频移键控(GMSK)调制的信号传输波形,采用一比特差分解调算法,对比解调波形与原始波形,分析复合信道对系统误码率性能的影响关系。模拟实验结果显示,与开关键控调制(OOK)、脉冲位置调制(PPM)相比,仅在海水衰减系数为
${\text{0}}{\text{.151}}\;{{\text{m}}^{-1}}$![]()
![]()
的衰减信道下,GMSK系统分别可获得
${\text{4}}{\text{.8}}$![]()
![]()
、
$ 3.3{\text{ dB}} $![]()
![]()
的信噪比增益。在复合信道下,GMSK调制性能明显优于OOK调制和PPM调制,当海水衰减系数为
${\text{0}}{\text{.151}}\;{{\text{m}}^{-1}}$![]()
![]()
、湍流对数强度方差小于0.16时,GMSK调制系统无误码率极限,系统误码率由信道的衰减、湍流特性和高斯噪声共同决定,GMSK调制相比于PPM调制获得
$4.35{\text{ dB}}$![]()
![]()
的信噪比增益;当湍流对数强度方差大于0.16时,系统存在误码率极限,极限值由湍流对数强度方差决定,且随着湍流对数强度方差的增加,系统极限误码率非线性递增。
水下无线光通信 复合信道 GMSK调制 湍流对数强度方差 误码率 underwater wireless optical communication composite channel GMSK modulation turbulence logarithmic intensity variance bit error rate 红外与激光工程
2022, 51(6): 20210622
光子学报
2022, 51(10): 1006006