A Coherent Phase-Diversity Optical Receiver with Double Frequency Conversion.

A "phase diversity" optical receiver uses homodyne detection on two separate branches to provide two orthogonal baseband outputs. Together, these outputs provide a complete characterization of the received optical signal. We present a design for a phase-diversity receiver that combines the advantages of heterodyne and homodyne detection while avoiding the need for the optical quadrature hybrid required by the conventional design. There is a reduction in receiver sensitivity of approximately 6 dB; however, in applications where ultimate sensitivity is not sought, the advantages of this design make it a very interesting alternative.