The WDM receiver includes a wavelength demultiplexer, a detector array and a signal extractor. The wavelength demultiplexer receives an n-channel optical input signal and transmits the n-channel optical input signal to m optical outputs. Each of the optical outputs receives a wavelength band centered at a different wavelength. The wavelength bands have a center-to-center wavelength spacing of . The detector array is composed of m detector elements coupled to the wavelength demultiplexer. Each of the detector elements generates a detection signal in response to light received from one of the optical outputs of the wavelength demultiplexer. The signal extractor receives the detection signals from the detector array and converts the detection signals to an n-channel receiver output signal, each channel of which corresponds to a different one of the n channels of the optical input signal. The WDM receiver is able to detect optical signals that are closely spaced in wavelength, even when the optical signals have off-center of varying wavelengths.