A tunable optical demultiplexer includes a control circuit and one or more heaters thermally coupled to waveguides of an optical demux. The control circuit is in signal communication with the one or more heaters and includes a processor coupled to a memory. The control circuit is configured to receive an optical channel group (OCG) identification signal and adjust the power delivered to the heaters in response to the OCG identification signal and based on parameter values stored in the memory. The optical demux outputs a plurality of optical signals at a corresponding one of a plurality of outputs. The transmission characteristics of the optical demux are varied depending on the amount of power delivered to the heaters. The varying of the transmission characteristics of the optical demux adjusts the spectral shifting of the plurality of wavelengths output by the optical demux.