PASSIVE, TEMPERATURE COMPENSATED TECHNIQUES FOR TUNABLE FILTER CALIBRATION IN BRAGG-GRATING INTERROGATION SYSTEMS

摘要

A passive, temperature compensated tunable filter calibration device for a Bragg grating interrogation system comprising a dual substrate Bragg grating interrogation system (21) in which the temperature of an array of gratins (12) is estimated using the array of gratings (12) bonded to a common host substrate (16) and a single grating (18) bonded to a material (22) with a different coefficient of thermal expansion. Changes in the common temperature of the substrates (16.22) is measured by monitoring the difference between shifts of grating wavelength. As a filter voltage is scanned from its lowest to its highest voltage, the voltages are recorded. The second lowest wavelength corresponds to the grating (18) attached to the differing substrate (22). The voltages are used to calculate a voltage to wavelength function for the scanning range of the filter (28). To compensate for variations in a calibration curve and temperature variations of the calibration array (12), the temperature is estimated and function re-calculated at every pass of the scanning filter (28).