Multi-Pulse Pulse-Position-Modulation Signaling for Optical Communication with Direct Detection

A modification of the traditional pulse-position modulation (PPM) scheme typically employed on the optical direct-detection channel is proposed that allows for significantly improved information throughput and bandwidth advantage. The scheme sends a multitude (K) of pulses per symbol interval and as such provides a signal constellation whose size, for a given number of pulse slots (M), varies as M (for large M) rather than linearly with M , as is the case for conventional PPM. Maximum performance improvement is obtained for deep-space optical communications applications, where narrow high-peak-power transmitted pulses offer significant advantages in terms of detection probabilities and background suppression capabilities at the receiver.