Performance of wireless optical communication systems Using DPSK modulation

A coherent differential phase-shift keying (DPSK) transmission system is presented to improve the receiver sensitivity for wireless optical communications. The error probability expression over atmospheric channels is derived under the assumption of log-normal distributed scintillation, and then the performance of DPSK system is compared with that of a most commonly used on-off keying (OOK) system under the same channel conditions. Theory analysis and numerical results illustrate that with the same bandwidth, DPSK system has a higher sensitivity than OOK, and to a certain extent DPSK format can reduce the impairment from turbulence-induced scintillation for its threshold being signal intensity insensitive, and hence, DPSK format is very suitable for atmosphere channels and has a broad prospect in wireless optical communications.