Multiplexing of Fbg sensor by light source intensity modulation

Abstract

Fiber Bragg grating (FBG) sensors are very useful and attractive in strain or temperature measurement, and they can measure at multiple positions by multiplexing techniques. A novel multiplexing technique with the intensity modulation of a light source was developed to use Bragg gratings of same Bragg wavelengths. A light source was modulated in triangular form at 1 MHz with an electro-optic modulator. Respective sensor signals had different time-delay and power levels due to the sensor positions from the modulated source and their spectrums. A simple signal processing could demodulate the received signals into independent sensor signals. One of the major advantages of this technique is the enhancement of signal-to-noise ratio (SNR) by a high-power source in comparison with the conventional time division multiplexing (TDM) using a pulsed source. A five-sensor system, which was operated in two different Bragg-wavelength ranges, was demonstrated to show the capability of multiplexing operation.