Crosstalk Suppression in the OFDR System Using a Dual-Wavelength wFBG Array

In this article, a dual-wavelength weak reflectivity fiber Bragg grating (wFBG) array was developed to suppress crosstalk in a wFBG-based distributed optical frequency-domain reflectometer system. In the newly developed array, two kinds of wFBG fabricated with different Bragg central wavelengths were arranged in an alternating pattern to replace the traditional identical wFBG. Crosstalk in the dual-wavelength array was theoretically simulated and experimentally measured and taken for comparative analysis with the identical array. Simulation and experiments indicate that the dual-wavelength array exhibits reduced crosstalk peak number and intensity, both of which facilitates demodulation and analysis of wFBG sensing. The signal-to-noise ratio (SNR) of the dual-wavelength array stands at 28.98 dB, which is 6.52 dB increased compared with the identical array. Lateral pressure sensing tests further prove the advantage of crosstalk suppression of the dual wFBG array. Lateral pressure sensitivity of the dual-wavelength array was measured to be 7.714 nm/ $\varepsilon $ with a pressure accuracy of $\pm 6.09~\mu \varepsilon $ , both of which exceed the performance of the identical array (7.438 nm/ $\varepsilon $ of lateral pressure sensitivity and $\pm 33.5~\mu \varepsilon $ of pressure test accuracy). Due to its simple structure, obvious crosstalk suppression, as well as SNR enhancement, the proposed dual-wavelength wFBG array would have extensive application prospects in distributed optical sensing fields.