Demodulation of a fiber Fabry-Perot sensor by a speckle-based silicon chip

Fabry-Perot (FP) interferometric sensors are widely employed for precise measurements of temperature, strain, and pressure. However, conventional demodulation methods face inherent trade-offs among accuracy, dynamic range, and real-time performance. Herein, we propose and experimentally validate a fiber FP sensor system based on a silicon-on-insulator (SOI) chip. The demodulation principle is on the basis of mapping environmentally induced spectral shifts into speckle patterns through multimode interferences. In this study, an Archimedean spiral bidirectional multimode waveguide (MMW) is employed to replace conventional multimode fibers, enabling higher integration, simplified packaging, and improved environmental robustness. The speckle patterns are subsequently converted into eight-channel intensity signals for easier data acquisition. In the demonstration experiments, a temperature measurement accuracy of 0.02°C was achieved while maintaining excellent long-term stability. Further analysis reveals that the employed SOI chip exhibits a wavelength sensitivity of 1 pm, corresponding to a theoretical temperature resolution better than 0.001°C. Overall, the speckle-based SOI chip provides a solution for FP sensor systems that features high precision, excellent stability, and a broad dynamic range.