In-phase and quadrature detection using 90° optical hybrid receiver: experiments and design considerations

140 Mbit/s ASK and DPSK optical hybrid receiver performance measurements are reported and discussed. The sensitivity of this type of receiver to polarisation misalignment is compared with that of a standard coherent (homodyne/heterodyne) receiver. The effects of laser phase noise and offsetting of the intermediate frequency from zero hertz are discussed along with other potential applications for 90° optical hybrid in-phase and quadrature receivers