Research on the Influence of Substrate Surface Roughness on the Sensing Performance of Fiber Bragg Gratings

The packaging process of fiber Bragg gratings (FBGs) directly determines the strain transfer efficiency, chirp occurrence, and sensing performance of the sensors. At present, relevant theoretical and experimental studies on the surface roughness of packaging substrates remain scarce. In this paper, combined with the theoretical model of interfacial debonding driving force and the sensing mechanism of FBGs, the FBG sensing performance under different substrate surface roughness conditions was investigated. Experimental results show that an excessively high substrate surface roughness will induce FBG chirp when the external strain reaches 1.143 × 10^-3, leading to the failure of strain transfer. In contrast, an excessively low surface roughness will weaken the interfacial coupling, thus reducing the strain response capability and cyclic stability of the sensor. The substrate surface treated by sandblasting with 150# abrasive exhibits the optimal comprehensive performance: The strain response capability of the FBG reaches 6.99994 × 10^-6 pm/ε with a linear fitting coefficient of 0.99994, presenting excellent linear response and cyclic stability. This study clarifies the optimal range of substrate surface roughness for FBG packaging and can provide theoretical and technical references for the packaging design and optimization of high-performance FBG sensors.