Performance analysis of multi-pulse pulse position modulation using avalanche photodiode in optical intersatellite links

The bit error rate (BER) performance of multipulse pulse position modulation (MPPM) using an avalanche photodiode (APD) is evaluated in optical intersatellite links (ISL's). We derive theoretical expression of BER of MPPM consisting of M slots and P pulses, referred to as (M, P) MPPM with output statistics of the APD which is approximated by Gaussian distribution. The BER performance of (7,2) MPPM and (9,2) MPPM is compared with that of 4-ary PPM under the conditions that bit rate is constant (200 Mbits/s) and that bandwidth is limited (slot time period is 2.5 ns). It is shown that (9,2) MPPM using the APD can achieve better BER performance than 4-ary PPM using the APD with broadening slot time period by about 10% under the condition that bit rate is constant or with improving bit rate by about 10% under the condition that bandwidth is constant when average photons/nat is somewhat large in achieving BER of 10^-9.