An apparatus includes a tunable optical carrier source configured to generate a tunable optical carrier and a fixed wavelength optical carrier source configured to generate a fixed wavelength optical carrier. The apparatus also includes first and second optical modulators configured to modulate the tunable optical carrier and the fixed wavelength optical carrier based on first and second of multiple input signals. The apparatus further includes a delay element configured to delay the modulated tunable optical carrier, first and second optical detectors coupled to the delay element, and third and fourth optical modulators coupled to the first and second optical detectors. In addition, the apparatus includes a wavelength division demultiplexer optically coupled to the third and fourth optical modulators, a plurality of optical 90-degree hybrid elements optically coupled to the wavelength division demultiplexer, and a plurality of optical detectors optically coupled to corresponding ones of the optical 90-degree hybrid elements.