Circuits and methods for photonic wavelength division multiplexers

A method comprising:

• providing a plurality of cyclic optical wavelength filters (COWFs) disposed in series in a plurality of stages;
• wherein
• each COWF in each stage of the plurality of stages except a last stage of the plurality of stages is coupled to a pair of COWFs within a next stage of the plurality of stages;
• the first stage of the plurality of stages coupled to a port for receiving a plurality of wavelength division multiplexed signals on a defined wavelength grid;
• each COWF of the plurality of COWFs within a stage of the plurality of stages has a free spectral range (FSR) equal to a predetermined fraction of the FSR of those COWFs within a succeeding stage of the plurality of stages;
• a subset of the plurality of stages comprising at least the first stage of the plurality of stages comprise phase shift elements (PSEs) for adjusting a characteristic of the COWFs within the subset of the plurality of stages;
• and
• the COWFs of the plurality of COWFs within the subsequent stages of the plurality of stages to the first stage of the plurality of stages are provisioned independent of PSEs for adjusting the characteristic of the COWFs within the subsequent stages of the plurality of stages to the first stage of the plurality of stages.