In the downlink, the transmission distance can be greatly enhanced by single-sideband modulation, which, based on an injection-locked semiconductor laser, is a much simpler solution.

• 在下行链路中，使用单边带调制可以提高光传输距离，而基于注入锁模半导体激光器的单模调制(单边带调制)是一种较为简单的方案；