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Synchronous Reflectivity Measurement of a Weak Fiber Bragg Grating Array Using Frequency-Shifted Interferometry

We demonstrate a method of reflectivity measurement for a weak fiber Bragg grating (FBG) sensor array based on frequency shifted interferometry. In the scheme, the measured weak FBG sensor array was connected after a referenced weak FBG, by using frequency shifted interferometry, the reflectivity of the referenced FBG and the reflection amplitude spectrum of each FBG from the sensor array were obtained, respectively, and then each grating reflectivity was iteratively calculated by using the spectral shadowing removal method. A sensor array of 60-weak FBGs with an average peak reflectivity around −25 dB was experimentally investigated. The obtained peak reflectivity ranged from −37.7 to −21.7 dB with an average value of −26.0 dB. Error analysis indicates the average reflectivity measurement stability for all FBGs was ±1.93 dB. The results reveal that this paper presents a feasible, simple, and low-cost method of reflectivity measurement for large-scale weak FBG sensor arrays.