Secure Coherence Modulation Telecommunication System

Abstract

Recently, with the rapid development of optical telecommunications, a considerable interest as been shown for secure optical transmission. Coding techniques which are not based on intensity modulation can potentially be adapted for secure transmission. Among the different techniques available, the most popular are probably based on frequency¹, phase², coherent correlation³, and coherence modulation⁴. The coherent schemes employ two interferometers illuminated by a Broadband Source (BBS) with a coherence length shorter than the interferometer’s Optical Path Difference (OPD). Information is encoded by modulating the emitter interferometer’s OPD. The constant optical power transmitted in such systems is attractive for secure communication since, “apparently”, a perfectly matched receiving interferometer is required to decode the signal.