Patent ID: 7580184

Claim:
A Gires-Tournois etalon comprising: an optical waveguide including a grating section in which a primary chirped Bragg grating, of a first reflectivity, a first central wavelength, and a first spectral bandwidth, is provided; and apparatus for inducing a low frequency periodic refractive index modulation within the grating section, wherein the addition of the low frequency periodic refractive index modulation to the primary chirped Bragg grating causes a secondary chirped Bragg grating, of a second reflectivity, a second central wavelength, and a second spectral bandwidth, to be excited, the first and second spectral bandwidths being substantially the same, the second reflectivity being lower that the first reflectivity, and being determined by the amplitude of the low frequency periodic refractive index modulation, and the second central wavelength being shifted from the first central wavelength by an amount determined by the frequency of the low frequency periodic refractive index modulation.