1 Gb/s Zero-IF DPSK Coherent Optical System Using a Single Photodetector.

We have demonstrated zero-IF DPSK coherent optical detection at 1 Gb/s without the use of multiple receivers and special optical couplers. To achieve this, we have added a 1 GHz sinusoidal phase switching signal to the NRZ phase modulator drive. The measured sensitivity of -37.5 dBm, compared with a theoretical estimate of -54.8 dBm, is impaired mainly by nonideal electronic circuits.