Sensitivity of optically preamplified DPSK receivers with Fabry-Perot filters

The error-rate performance of a DPSK lightwave receiver having an optical amplifier followed by a Fabry-Perot filter and delay-line demodulator is analyzed. Receivers with sampling and with integrate-and-dump threshold comparison are compared to the well-known result for a matched optical filter. The Fabry-Perot filter decreases the sensitivity at 10/sup -9/ error-rate from 20 to 24.5 photons/b with optimum optical filter bandwidth and postdetection integration time.