OPTICAL CDMA SYSTEM

摘要

An optical fiber communications system uses spread spectrum code division multiple access techniques to achieve better bandwidth utilization. A single encoding mask having a first code is used to encode the optical signal. Light, spatially encoded by the mask and temporally modulated with data, is transmitted over a fiber link and received by a decoder. A polarization insensitive separator splits the received light into two equal power components which are provided to two decoding masks used to decode the signal. One of the masks has a second code identical to the first code and the other mask has a third code complementary to the first code. The output light beams filtered by the masks are differentially detected to generate an output signal, which is further processed for data recovery. The electrical signal is low pass filtered and electrically square law detected. The first codes are selected from a set of unipolar codes derived from a set of balanced bipolar orthogonal codes. The codes may be either binary or analog.