Patent ID: 6175670
Filing Date: 2001-01-16
Classification: G02B

Abstract:
A planar lightguide circuit comprising:a substrate;on said substrate a first planar lightguide having a first effective index of refraction and transmitting a plurality of wavelength division multiplexed signals;on said substrate a second planar lightguide having a second effective index of refraction different from said first effective index of refraction and in close proximity and parallel said first planar lightguide in a first region; anda first planar grating in coupling proximity to said first and second planar lightguides to backward couple a first signal of a selected wavelength from said first planar lightguide to said second planar lightguide;said first and second planar lightguides extending to ports at a first edge of the planar lightguide circuit,on said substrate a third planar lightguide in close proximity and parallel in a third region to said first planar lightguide and having a third effective index of refraction different from said first effective index of refraction; anda second planar grating in coupling proximity in said third region to said third planar lightguide and said first planar lightguide to backward couple a second signal of a selected wavelength to said third planar lightguide from said first planar lightguide, wherein the first, second, and third planar lightguides are arranged to extend to ports only at said first edge.