A multiple band pass optical filter comprises an interferometer, such as a Michelson interferometer, with de-tuned reflective Bragg gratings 8, 9 that produce multiple, separate, substantially equal reflectivity pass bands for light passing from the interferometer's input port P1 to output port P2....http://www.google.fr/patents/US6141469?utm_source=gb-gplus-shareBrevet US6141469 - Multi-band-pass filter
