Abstract

In free space laser communication systems, the rejection of the optical background radiation is a serious problem. We have designed a direct detection building-to-building optical communication system that uses a Faraday Anomalous Dispersion Optical Filter (FADOF) in the receiver. The system block diagram is shown in Fig. 1. The FADOF is an narrow bandpass optical filter, which can provide a background rejection of 10⁵ while transmitting the signal with up to 80% efficiency. The FADOF also has a signal bandwidth that is variable between 0.5 GHz and 5 GHz, a field-of view that is flat over ±20°, and excellent imaging qualities. So it promises to offer new capabilities to free space laser communication and effectively reduces the solar background radiation that reaches the photodetector by three orders of magnitude compared with an interference filter.

© 1993 Optical Society of America