Fiber Bragg grating temperature sensor using a silicon waveguide chip

Speckle demodulation technology offers a highly accurate method for measuring minute wavelength shifts in fiber Bragg gratings (FBGs) by analyzing speckle patterns resulting from intermodal interference within scattering media. In this study, a silicon waveguide chip is utilized as a substitute for multimode fibers as the scattering medium, thereby enhancing the robustness of the temperature demodulation system. Furthermore, sparse sampling with a photodiode (PD) array is implemented in place of a CCD camera, significantly improving acquisition speed while reducing the overall system size and cost. A low-complexity lookup table approach is adopted for temperature demodulation, minimizing computational demands and facilitating real-time processing. Experimental results indicate that the proposed system achieves temperature demodulation with an accuracy of less than 1°C for a single FBG, demonstrating its potential for application in multi-FBG demodulation scenarios.