Automatic Bias Control for PPM-Based Free Space Optical Communication Systems

Pulse position modulation (PPM) is widely adopted by free space laser communication system due to high energy efficiency. The performance of PPM-based system is greatly affected by the extinction ratio (ER) of optical transmitter due to the fact that ER contributes to a non-negligible proportion of background noise. In this paper, we present a practical automatic bias control (ABC) algorithm to maximize ER of optical PPM signal and build a experimental demonstration system. The experiments show that the proposed ABC algorithm can retain ER at 24 dB during a long continuing operation.