Bandwidth Requirements for Optical DPSK Communication.

The effect of restricted electronic banwidth on the signal- to-noise ratio of a lightwave DPSK system in the shot-noise limited regime is studied via simulated time-domain responses. Bandwidth requirements at the transmitter are found to be rather severe for this non-linear system. A transmitter with a cut- off frequency placed at the bit rate (1/T) results in a 3 dB penalty, due mostly to signal (eye pattern) distortion. The receiver, however, requires only a third of this bandwidth for the same penalty. A low-pass intermediate frequency stage with a cut-off frequency set at 80% of (f sub(IF) + 1/T) also results in about 3 dB of penalty.