A WDM receiver that includes a single, delay interferometer coupled to an N-channel wavelength-demultiplexing filter provides for the simultaneous conversion of a multiplex of N differential-phase-shift-keyed modulated optical signals of different wavelengths into N intensity-modulated optical signal channels. The Nintensity-modulated optical signals may be individually detected by a bank of N photodiode circuits to recover the modulated data stream or used for optical amplification, regeneration, processing, control, or modulation.