Tight lower bounds on capacity and cutoff rate of DOPPM in optical direct-detection channel

Differential overlapping pulse position modulation (DOPPM) can achieve higher capacity and cutoff rate than PPM, DPPM and OPPM when the pulsewidth and the average power of the channel are constrained. Previously (Ohtsuki et al., 1994) erasure events of one pulsed chip that can be decoded correctly were defined as an erasure event. This results in loose lower bounds on the performance. This summary analyzes the tighter lower bounds on capacity and cutoff rate of DOPPM in the optical direct-detection channel. Considering what pulsed chips we have to detect to decode the words correctly, we derive the transition probability of DOPPM words and the tighter lower bounds in the optical direct-detection channel.