Periodic arrayed waveguide grating multiplexer/demultiplexer

An optical multiplexer/demultiplexer for multiplexing/demultiplexing a plurality of sub-bands of optical channel frequencies, each sub-band having M adjacent channel frequencies comprising:

• a periodic dispersive optical element having a free spectral range equal to an integer multiple N times a frequency width of a sub-band of M channels, where N is greater than 1, said periodic light dispersive optical element optically coupling a plurality of individually selectable inputs N, equal to the integer multiple, spatially separated to provide selected input sub-band frequencies spectrally separated by substantially M*Δf, for launching light into the periodic dispersive optical element in a demultiplexing mode of operation, or for outputting a multiplexed band of adjacent channels in a multiplexing mode of operation;
• and,
• a plurality of outputs M, separated to provide a spectral frequency interval of Δf, for receiving M demultiplexed channels of a sub-band from the periodic dispersive optical element in a demultiplexing mode of operation, or for launching a plurality of adjacent channels into the periodic dispersive optical element in a multiplexing mode of operation.

A method of demultiplexing a sub-band of M adjacent optical channels from a plurality of optical channels having a channel spacing of Δf comprising the steps of:

• demultiplexing a sub-band of M multiplexed channels from the plurality of optical channels;
• launching the sub-band of M channels into a selected input of a periodic dispersive optical element having a plurality N of inputs spatially separated to provide a spectral separation of substantially M*Δf and a plurality M of outputs, spatially separated to receive output spectral frequencies separated by Δf, and a free spectral range equal to substantially N*M*Δf;
• distributing to the M outputs a periodic order of the dispersive optical element comprising M channel frequencies.