NTEGRATED COHERENT RECEIVER HAVING A SINGLE MMI COUPLER OPTICAL HYBRID, NON-INTERSECTING OPTICAL PATHS AND UNIFORM ELECTRICAL PATHS

A coherent receiver optical sub-assembly photonic integrated circuit has optical input ports, electrical output ports, photodetectors, and a single multi-mode interference (MMI) coupler. The optical input ports receive a phase modulated optical signal (S) and a continuous wave local oscillator (LO) optical signal. The electrical output ports output electrical signals corresponding to mixing products of the S and LO optical signals. The photodetectors are connected to the electrical output ports through electrical lines. The MMI coupler has a main body, input access waveguides, and output access waveguides. The input access waveguides receive the S and LO optical signals from the input ports and launch light to the main body. The output access waveguides are connected to respective ones of the photodetectors through optical waveguides. The output access waveguides collect multi-mode interference signal products from the main body and deliver the mixing products of the S and LO optic signals.