Compensation of temperature-induced fluctuation in fiber-Bragg-grating vibration sensor by using feedback control of source wavelength

The operation of a fiber Bragg grating (FBG) vibration sensor, which is based on the intensity-modulation method, is stabilized by compensating the fluctuation of the sensitivity induced by the environmental temperature change. The compensation is realized by controlling the oscillation wavelength of the source laser with a feedback circuit so that the operation point on the FBG transmittance spectrum curve should remain the same regardless of the temperature change. The variation of the sensitivity is reduced to as small as 1 dB over the temperature range from -15 to 50 degrees Celsius, although it is more than 60 dB without the stabilization.