Crosstalk tolerance of direct detection differential phase-shift keying optical systems in the presence of receiver imperfections

An analytical method based on the knowledge of the moment generating function of the decision variable, which permits to assess the in-band crosstalk tolerance of direct detection differential phase-shift keying (DPSK) optical systems with receiver imperfections relatively to conventional on-off keying systems, is presented. It is shown that the crosstalk tolerance of DPSK systems can be greatly reduced or even disappear when the receiver imperfections are taken into account.