Patent ID: 7260292

Claim:
A spectrally selective optical coupler, comprising a first optical fiber having a light guiding core arranged to guide light along a predetermined path, and a cladding surrounding said core; a deflector provided in said core, operative to deflect at least part of any light propagating in the core out from the fiber under an angle that avoids total internal reflection between the cladding and a medium surrounding said cladding; and an external lightguide defined by at least a first reflecting surface and a second reflecting surface, wherein the optical fiber is positioned between said first reflecting surface and said second reflecting surface, wherein the deflector is arranged to deflect light, within a predetermined wavelength range, from said core into a propagating mode of the external lightguide, and wherein the separation between said first reflecting surface and said second reflecting surface of the external lightguide is adjustable, such that the allowed wavelength range of the propagating mode can be tuned.