Overlapping multi-pulse pulse position modulation in optical direct detection channel

Overlapping multi-pulse pulse position modulation (OMPPM) is proposed in an optical direct-detection channel to improve the information rate and efficiency over pulse position modulation (PPM) or multi-pulse PPM (MPPM). The error probability of an uncoded OMPPM system is investigated in an optical direct-detection channel in the quantum limited case. Both capacity and cutoff rate are evaluated in this channel. Reed-Solomon (RS) codes are employed for OMPPM to achieve high energy information efficiency in the high throughput range. It is shown that OMPPM outperforms on-off keying (OOK), PPM, and MPPM in terms of both capacity and cutoff rate for the same bandwidth and the same probability of pulse occurrence. It is also shown that RS-coded OMPPM achieves high energy information efficiency, even in the range of high throughput