An optical, multi-channel, 
Differential Phase Shift 
Keying (DPSK) 
receiver demodulates multiple 
Wavelength Division Multiplexed (WDM) channels using at least one interferometer. This distributes expense of the interferometer(s) over all channels of an optical 
signal, allowing for deployment of cost-effective, scalable, 
wideband, WDM DPSK systems. For example, for an 80 channel WDM link, the 
receiver uses a single interferometer instead of eighty interferometers and associated stabilization hardware, dramatically reducing size, weight, power, and cost. The 
receiver is architecturally compatible with existing interferometer technologies so previous development and qualification efforts can be leveraged. This allows for expedited technology 
insertion into existing optical communications networks, including terrestrial and space-based optical networks.