Patent ID: 7538860

Claim:
A system for determining a reflection wavelength of multiple low-reflectivity Bragg gratings in a sensing optical fiber having a broadband reflector and a plurality of the Bragg gratings at different distances from the broadband reflector along a length of the sensing optical fiber, the system comprising: a source laser coupled to the sensing optical fiber; an optical detector coupled to the sensing optical fiber and configured to detect a reflected signal from the sensing optical fiber; a plurality of frequency generators, each frequency generator configured to generate a signal having a frequency corresponding to an interferometer frequency of a different one of the plurality of Bragg gratings; a plurality of demodulation elements, each demodulation element coupled to the optical detector and to a different one of the plurality of frequency generators, each demodulation element configured to combine the signal produced by a different one of the plurality of frequency generators with the detected signal from the sensing optical fiber; a plurality of peak detectors, each peak detector coupled to a different one of the demodulation elements and configured to detect a peak of the combined signal from a different one of the demodulation elements; and a laser wavenumber detection element coupled to the peak detectors and configured to determine a wavenumber of the laser when any of the peak detectors detects a peak.