基于高灵敏度光电探测器的长距离光通信OFDM系统设计

Design of long-distance optical communication OFDM system based on high sensitivity photodetector

摘要:

长距离光通信存在低信噪比、高衰减特性,使得传输信道的非线性特性会引发相位畸变,会破坏传统正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)系统的子载波正交性,难以补偿从时域转换为频域信道的相位畸变情况,导致长距离光通信信号的解调误码率较高。针对上述瓶颈,构建一种基于高灵敏度光电探测器的长距离光通信OFDM系统。在硬件层面,系统集成高性能正交调制器、分布式拉曼放大器与超高响应度光电探测器,分别实现高质量光信号生成、链路损耗补偿与微弱信号的高精度检测；在软件层面,设计包括抗相位畸变的OFDM信号生成,补偿从时域转换为频域信道的相位畸变,联合时频域均衡实现从信号生成到解调的全流程优化。实验结果表明,所提系统可实现最高65 dB的OFDM信号信噪比、68%的光纤链路损耗补偿率及最低1.5%的解调误码率,显著提升了长距离传输条件下的系统鲁棒性与通信质量。

Abstract:

Long-distance optical communication has the characteristics of low signal-to-noise ratio and high attenuation, which makes the nonlinear characteristics of the transmission channel cause phase distortion and disrupt the subcarrier orthogonality of the traditional Orthogonal Frequency Division Multiplexing (OFDM) system. It is difficult to compensate for the phase distortion when converting from the time domain to the frequency domain channel, resulting in a relatively high demodulation error rate of long-distance optical communication signals. To address the above-mentioned bottlenecks, a long-distance optical communication OFDM system based on high-sensitivity photodetectors is constructed. At the hardware level, the system integrates high-performance orthogonal modulators, distributed Raman amplifiers and ultra-high responsibilance photodetectors, respectively achieving high-quality optical signal generation, link loss compensation and high-precision detection of weak signals. At the software level, the design includes the generation of OFDM signals resistant to phase distortion, compensation for phase distortion when converting from the time domain to the frequency domain channel, and joint time-frequency domain equalization to achieve full-process optimization from signal generation to demodulation. The experimental results show that the proposed system can achieve a maximum signal-to-noise ratio of 65 dB for OFDM signals, a fiber link loss compensation rate of 68%, and a demodulation bit error rate of the lowest 1.5%, significantly improving the system robustness and communication quality under long-distance transmission conditions.