空间激光通信高速多制式光调制技术

Multi-format Optical Modulation Technique with High Bit Rate for Space Laser Communication

摘要:

空间激光通信调制技术以幅度调制和相位调制为主,单一通信终端只能适应特定的调制格式,灵活性较差,存在星间链路组网应用的局限性。文章基于数字处理的光调制技术,采用LiNbO₃晶体正交相位调制器,结合闭环偏压控制算法,实现了光调制格式、调制速率可变的星载光调制器,并针对空间应用对幅度调制和相位调制方式进行了优化,最大化光纤放大器效率。该技术硬件实现了625Mb/s~5Gb/s通信速率分档可调,OOK,BPSK和QPSK调制格式可变,发射EVM优于9%,实际引入灵敏度损耗小于1dB。该调制器已经完成所有空间环境试验,可广泛适用于各种体制的激光通信终端,进行星地、星间激光通信建链。同时,该调制器具备模拟调制的功能,可实现星间微波光子信号的透明转发。

Abstract:

The amplitude modulation and phase modulation are the key techniques in laser communication systems, but there is a limitation in satellite network with inter-satellite links as single laser terminal can only have a specific modulation format. In this paper, an optical modulation technique which is compatible with multi-modulation formats and bit rates based on digital processing was described. A LiNbO₃ quadrature modulator combined with closed-loop bias control algorithm was applied to implement amplitude modulation (OOK modulation) , phase modulation(BPSK modulation) and multilevel phase modulation (QPSK modulation) in a signal modulator. The modulation bit rate can be tuned from 625Mb/s to 5Gb/s according to different modulation formats of OOK, BPSK and QPSK. The transmission EVM is less than 9% with coding and scrambling functions and the inducted loss for the receiving sensitivity is less than 1dB. This modulator has been verified in all environment experiments such as vibration test, thermal vacuum circle test and radiation test and could be used in various laser communication terminals. The modulator realizes the function of analog modulation, so it is expected to be used as a transparent transponder for microwave photonic signal.