Patent ID: 6650810
Filing Date: 2003-11-18
Classification: G01J,G02B,G02F

Abstract:
An apparatus for matching a known waveband spectrum of a selected substance, the apparatus comprising:an optical waveguide having a core material, a nominal core refractive index, an input end and an output end wherein the optical waveguide transmits light energy from the input to the output end through the core material; a plurality of periodic variations in the refractive index carried in the optical waveguide core between the input and the output ends, said periodic variations being chosen to change the nominal core refractive index to reflect selected wavelengths of light back toward the input end to produce a reference spectrum having characteristic wavelengths matching the known spectrum of the selected substance; and a modulator coupled to the optical waveguide to modulate the periodic variations in the core refractive index to selectively and intermittently shift the reflected wavelengths of the optical waveguide.