Optical PPM synchronization for photon counting receivers

The performance of two signal synchronization schemes for photon counting receivers used in optical PPM communication systems operating in low-flux conditions, such as proposed deep space optical communication links, are analyzed. The pilot symbol insertion and inter-symbol guard time synchronization schemespsila performance are compared under conditions of equal throughput and equal peak or average power at representative operating points, including frequency offset due to transmit and receiver oscillator instability.