Fiber Optic Sensors and Interrogation Systems
Publishing Time:2016-12-26

2. Time-division Multiplexing (TDM) Demodulation System

In recent years, Fiber Bragg grating sensor technology has become a new development orientation in the sensor field. It has some performances such as light weight, electromagnetic immunity, corrosion resistant, easy to access into fiber optic sensor networks etc., it’s widely used in aerospace, oil and electric power, civil engineering, biochemistry and medicine. The multiplexing of FBG is very important for fiber optic sensing system, the widely used multiplexing technology are WDM and TDM. In WDM system, each sensor occupies a spectral range and the number of sensors is limited by the bandwidth of light source. In TDM system, the light source is work in pulse mode, an optical switch is driven by a pulse generator, when the period of pulse signal is equal to the round trip time between optical switch and FBG, the sensor signal could pass through the optical switch, each sensor can be addressed by tuning the period of pulse signal. Our group focuses on:

(a) A novel fiber Bragg grating (FBG) sensor system for measurement of strain and temperature is proposed.

(b) A semiconductor optical amplifier (SOA), connected in a ring cavity, is used to serve as a gain medium and switch.

(c) A large capacity multiplexing technology with mixed TDM+WDM is proposed.

(d) Based on TDM+WDM technology, a two dimensional FBG sensing network with 5×5 sensor array is build up, the stress/temperature distribution of an aluminum plate is measured under different loading/heating by using this FBG network.

Fig.1 Schematic of temperature distribution