Patent ID: 7715005

Claim:
An optical sensor comprising: a substrate; at least two planar Bragg gratings defined within one or more optical waveguides in the substrate, each Bragg grating having a wavelength filtering response that varies with an effective modal index experienced by light propagating in the Bragg grating and that has a characteristic Bragg wavelength different from the Bragg wavelengths of the other Bragg gratings; and at least one sample window overlying and associated with at least two of the Bragg gratings and arranged to receive a sample of fluid such that the presence of a sample of fluid affects the effective modal index experienced by light propagating in the associated Bragg gratings and hence modifies the wavelength filtering response of those Bragg gratings; the Bragg gratings being arranged to receive light from a light source, filter the light by reflection, and output the filtered light reflected from the Bragg gratings for detection by a spectrally resolving optical detector or an optical power detector.