Patent ID: 6573489
Filing Date: 2003-06-03
Classification: G01K,G02B,H04B

Abstract:
A passive, temperature compensated tunable filter calibration device in a Bragg-grating interrogation system comprised of:a first array comprised of a plurality of Bragg gratings bonded to a first host substrate and a single Bragg grating bonded to a second host substrate having a different coefficient of linear thermal expansion; said first array forming a calibration and reference device; said grating comprising the first array being place on a single optical fiber strand; a second array having a plurality of Bragg gratings bonded to a single optical fiber comprising a sensing array for monitoring strain, temperature, and other measurands capable of being measured with fiber Bragg gratings; a broadband light source producing a broadband optical light; a scanning filter for filtering the optical light so that at any point in time only a narrow band of light is present in the first and second arrays; means for applying a drive voltage to the filter so that the passband of the filter scans the wavelength of the wavelength in a region of interest; a first and second photodetector for receiving reflected optical light signals from the first and second arrays for converting these optical signals to electrical signals; a first and second amplifier associated with said first and second photodetectors for conditioning the signals for further processing; means for sampling the drive voltage when the passband of the filter coincides with the Bragg wavelength of one of the gratings in either array; processing electronics for detecting peaks in a voltage waveform and triggering a sampling device; and said processing electronics calculating the temperature of the reference device and voltage-to-wavelength function for the scanning range of the filter.