High-speed Identical Weak Fiber Bragg Grating Interrogation System Using DFB Laser

A high-speed fiber Bragg grating(FBG) interrogation system is realized by using the high-speed sweep characteristic of Distributed feedback(DFB) laser to constitute a high-speed wavelength-swept laser. To solve the problem of narrow scanning width of the DFB laser and low reuse capacity of the system, the method of building a time division multiplexing(TDM) sensor network with identical weak fiber Bragg grating is proposed. By using the transmission delay of light between the gratings to separate the grating reflection spectrum in time-domain and demodulating the reflection scanning spectrum of each grating to realize the wavelength demodulation. Experimental results show that, under a constant interrogation frequency on 100kHz of the system, 10 identical weak FBGs with the center wavelength of 1553.7nm and reflectivity of 1% have achieved demodulation in a single fiber. And within the temperature range from 25 degrees C to 79 degrees C, the linearity of each FBG's center wavelength varying with the temperature reaches 0.99.