Synchronization for optical overlapping pulse-position modulation systems

Abstract

In direct-detection optical communication, overlapping pulse-position modulation (OPPM) was shown to exhibit some advantages over pulse-position modulation (PPM). OPPM is a modification of PPM allowing overlapping between adjacent pulse-positions (many pulse-positions per pulsewidth). As such, it has a higher transmission rate than PPM for the same pulsewidth duration, while retaining the same advantages that make PPM desirable for direct-detection optical channels, such as low duty-cycle and ease of decoding. In this dissertation the problems of synchronizability and detectability of OPPM sequences as well as the problems of symbol synchronization and frame synchronization and frame synchronization sequence selection are studied. Maximum-likelihood rules are derived as well as suboptimal, easily implemented approximations to the optimal rules. Performances of these rules are verified through computer simulations. Performance upper bounds which respect to each rule are derived and used as a basis for comparison.