星地激光通信中光学数字相干接收机的研究

光学数字相干接收技术在星地激光通信中具有广泛的应用前景。本文以窄线宽DFB激光器作为光源,采用自动频率控制环路,结合光学混频和数字信号处理技术,实现了最高速率为1.25 Gbps的相干光通信。实验结果表明,自动频率控制环路能够将信号光和本振光之间的频率差实时控制在10 Hz以内,光学混频器输出的I、Q两路信号相位差能够长时间稳定保持90°,基于FPGA的载波相位补偿技术能够有效修正自动频率控制环路的相位残差,在误码率为10-6条件下,该接收机的灵敏度优于每比特54个光子。

Research on digital coherent optical receiver for satellite to ground laser communication

Digital coherent optical receiver has a wide application prospect in the next generation satellite to ground laser communication.Taking the narrow line width DFB laser as local oscillator,combined with 90° optical mixing and automatic frequency control(AFC) loop,a coherent light communication of 1.25 Gbps is realized.The experimental results indicate that the AFC loop can make the frequency difference between signal light and local light keep within 10 Hz,and the phase difference between I branch and Q branch will keep 90° strictly for a long time.The carrier phase compensation technique based on the FPGA can effectively correct the phase residual errors of AFC loop.The sensitivity of the receiver is superior to 54 photons per bit at error rate of 1×10-6 bit.