Patent ID: 8620121

Claim:
A fiber retroreflector comprising: a fiber having a diameter; and a tapered section located at an end of the fiber, having a core having a refractive index n 0 ; a first cladding means surrounding the core, the first cladding means having a refractive index n 1 ; a second cladding means surrounding the first cladding means, the second cladding means having a refractive index n 2 , wherein n 0 , n 1 , and n 2 are such that n 0 >n 1 >n 2 ; a beginning having a beginning diameter; an end having an end diameter; and a length therebetween, wherein the diameter of the tapered section gradually decreases over the length thereof, from the beginning diameter to the end diameter thereof, such that a substantially singlemode core-confined light, traveling from the beginning to the end of the tapered section, ceases to be substantially confined to the core, expands into the first cladding means, and becomes guided, while remaining substantially singlemode, by a waveguide formed by the first cladding means and the second cladding means; and wherein said tapered section has a reflective surface at the end thereof for reflecting a light back through said tapered section, so that the reflected light is coupled back into a core mode of the fiber.