All-optical signal encoder-decoder for secure communications

Direct sequence spread spectrum (DS/SS) is often employed for non-centralized multiple access, and an added degree of system security in coherent optical communications. With advances in coherent optical processing using Spatial- Spectral Holographic (SSH) Devices, it is possible to implement an all optical encoder/decoder for M-ary phase shift keying DS/SS. We address the issue of code selection of length N code sequences drawn from an alphabet consisting of M unit length phasers and designed for a multiuser environment. The codes are selected using very fast simulated re-annealing based on the criterion of minimizing the periodic auto and cross correlation sidelobes. The all optical implementation is discussed.