A planar lightwave circuit (PLC) includes a substrate, a tunable filter, a demultiplexer (DEMUX), and an optical processor each disposed on the substrate. The tunable filter is configured to filter at least one of a bandwidth or a wavelength of a Wavelength Division Multiplexed (WDM) optical input signal. The DEMUX is connected to the tunable filter and configured to receive a filtered WDM optical input signal at an input and to supply one of a plurality of channels of the filtered WDM input signal at a respective one of a plurality of outputs. Each of the plurality of channels corresponds to one of a plurality of wavelengths of the filtered WDM input signal. The optical processor includes a bit-delay interferometer communicating with a respective one of the plurality of outputs of the DEMUX. The optical processor is configured to receive one of the plurality of channels from the DEMUX and output a plurality of demodulated optical signal components.