A wavelength division multiplex/demultiplexer (WDM) has a plurality of narrow-band zeroth order resonant grating filters (10a-10e) to multiplex or demultiplex multiple wavelengths that have very close channel spacing. In one embodiment, a plurality of these filters (10a14 10e) are assembled in a block...http://www.google.ca/patents/US6212312?utm_source=gb-gplus-sharePatent US6212312 - Optical multiplexer/demultiplexer using resonant grating filters
