激光频率波动对内差相干通信载波恢复性能的影响分析

Analysis of influence of laser frequency fluctuations on carrier recovery performance in intradyne coherent laser communication

摘要:

搭建内差相干激光通信系统频率波动模型，对比分析BPSK和QPSK两种信号在不同频率波动条件下和Viterbi-Viterbi滤波器长度时的载波恢复性能。结果表明，当系统的工作状态稳定后，在激光频率波动幅度和波动频率较小时，两种信号的光信噪比损失平均值均小于0.5dB；随着波动幅度和波动频率的逐渐增大，Viterbi-Viterbi滤波器的长度越大，光信噪比损失就越严重。当Viterbi-Viterbi滤波器长度分别为7和11时，两种信号载波恢复性能良好。此时，BPSK信号由波动幅度引起的光信噪比损失平均值分别为0.11dB和0.16dB，由波动频率引起的光信噪比损失平均值均为0.15dB。而QPSK信号由波动幅度引起的光信噪比损失平均值分别为1.7dB和2.9dB，由波动频率引起的光信噪比损失平均值均为0.8dB。因此，对于相同的Viterbi-Viterbi滤波器长度、波动幅度和波动频率，BPSK信号的抑制激光频率波动能力优于QPSK信号。

Abstract:

The intradyne coherent laser communication system with laser frequency fluctuations model is built, and the carrier recovery performance of BPSK and QPSK signals with different laser frequency fluctuation and Viterbi-Viterbi filter lengths are compared and analyzed. It shows that when system is stable, the optical signal-to-noise ratio(OSNR) penalty of two signals is less than 0.5dB at the slight fluctuation amplitude and fluctuation frequency. As the fluctuation amplitude and frequency increase gradually, the OSNR penalty is increasing as the Viterbi-Viterbi filter length values increase. When Viterbi-Viterbi filter lengths are 7 and 11, the two kinds of signals show high performance. For BPSK signals, the average of OSNR penalties caused by fluctuation amplitude are 0.11dB and 0.16dB respectively, and the average of OSNR penalties are both 0.15dB caused by fluctuation frequency. At the same time, for QPSK signal, the average of OSNR penalties caused by fluctuation amplitude are 1.7dB and 2.9dB respectively, and the average of OSNR penalties are both 0.8dB caused by fluctuation frequency. Therefore, for the same Viterbi-Viterbi filter length and fluctuation, the ability of BPSK signal to suppress laser frequency fluctuations is better than that of QPSK signal.