Patent ID: 6917735
Filing Date: 2005-07-12
Classification: G01J,G02B,H01S

Abstract:
1. Apparatus for interrogating an optical signal propagating in an optical waveguide, the apparatus comprising: an optical waveguide having a grating portion along which the refractive index of the waveguide vanes periodically, the said variation giving the grating portion a spectral profile having a first region across which the transmitted optical power is substantially constant as a function of wavelength and a second region across which the transmitted optical power changes as a function of wavelength, the said variation of refractive index causing at least part of the optical signal to be coupled out of the grating portion of the waveguide, wherein when said optical signal is of a wavelength falling within said second region the optical power of said outcoupled optical signal changes as a function of said wavelength, and first optical means operable to measure the optical power of an outcoupled optical signal, from which the wavelength of said optical signal having a wavelength falling within said second region can be determined.