Simplifying the error probability analysis in optical direct detection DPSK systems

This letter describes a rigorous formulation based on an eigenfunction expansion technique to estimate the performance of optical direct detection DSPK systems and discusses appropriate procedures to simplify the process without solving any eigenvalue problem. A great emphasis is put on an approach derived from the wide-band optical filtering assumption. The results show that this simplification is acceptable for ideal receivers with time-bandwidth products far larger than 1, but it is clearly inadequate for more realistic receivers.