A WDM transmitter and/or receiver optoelectronic integrated circuit includes a plurality of microresonators and corresponding waveguides and couplers that are integrally formed on a substrate. For the WDM transmitter, the microresonators and waveguides are configured to generate a plurality of optical signals at different wavelengths. Each coupler includes a resonant cavity waveguide that is configured to transmit one optical signal from one waveguide to the output waveguide such that the plurality of optical signals are multiplexed on the output waveguide. For the WDM receiver, an input waveguide is configured to provide for propagation of a plurality of optical signals at different wavelengths. Each coupler includes a resonant cavity waveguide that is configured to transmit at least one optical signal from the input waveguide to one waveguide. The waveguides and microresonators are configured to perform optical-to-electrical conversion of the plurality of optical signals at different wavelengths that propagate in the waveguides.