Thermally Stabilized Fiber-Bragg-Grating Vibration Sensor Using Servo Motor Control

A fiber-Bragg-grating (FBG) vibration sensor, in which an FBG acts as an intensity-modulator for incident narrow spectrum light such as a laser, is thermally stabilized. Sensitivity of the sensor is kept constant over a wide range of temperature by feeding back a fraction of the output signal into the laser source in such a way that by shifting the oscillation wavelength of the laser the dc component of the detected photocurrent remains unchanged regardless of change in the environmental temperature. Variation in the sensor sensitivity is reduced to as small as 3 dB after the stabilization, although it is more than 55 dB without the stabilization.