Intensity-modulated multiplexing of fiber Bragg grating sensors

Abstract

Fiber Bragg grating sensors are very useful and attractive for strain or temperature measurement, and they can measure at multiple positions through the use of multiplexing techniques. This paper presents the development of a novel multiplexing technique using intensity modulation of a light source. 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 with respect to the modulated source and their spectra. A simple signal processing scheme could be used to demodulate the received signals into independent sensor signals. One of the major advantages of this technique is the enhancement of the signal-to-noise ratio by a high-power source in comparison with conventional time division multiplexing using a pulsed source. A five-sensor system, which was operated over two different Bragg wavelength ranges, was demonstrated.