Large WDM FBG Sensor Network Based on Frequency-Shifted Interferometry

We combine wavelength-division multiplexing (WDM) and frequency shifted interferometry (FSI) to interrogate a large-scale ultra-weak fiber Bragg grating (FBG) array. Based on Sagnac interference, FSI can location resolve sensors without using pulses or fast detection, therefore considerably lowers the system cost. By combining FSI with WDM, higher spatial resolution can be achieved. We demonstrated simultaneous interrogation of 363 FBG sensors, grouped into 121 identical units of 3 FBGs of different central wavelengths and spaced two meters apart. Based on the performance of the 363 grating system, we show the potential for interrogating 3207 sensors with good signal-to-noise ratio. Stability test and temperature sensing were carried out, and the obtained temperature resolution was ± 0.4 ° C. The results indicate the proposed scheme can greatly enhance the multiplexing capacity and meet the requirements of large-scale optical fiber networks.