Comparison of theoretical calculation and experimental testing of the sensitivity of a fiber Bragg grating strain sensor

A Distributed Fiber Optic Sensing (DFOS) system has been successfully developed by RC Integrated Systems LLC (RISL). The DFOS system is capable of providing simultaneous measurement of multiple parameters such as temperature, strain, and pressure for harsh environment applications. DFOS sensors are based on fiber Bragg gratings (FBGs) and coating of a unique high-temperature-resistant (HTR) material on the surface of silica optical fibers. DFOS sensors have been tested to withstand temperatures up to 1,100 degrees C and have great potential for high temperature environment applications. In this work, we were focused on the application of DFOS FBG sensor for strain measurement. A numerical model was established to simulate the FBG response to the applied strain. To verify the modeling result, a simple experimental setup was assembled to measure the sensor's sensitivity for strain measurement at room temperature. Experimental testing shows that the FBG sensitivity for strain measurement is 1.1957 pm/mu epsilon which is consistent with the numerical modeling results. The difference between the measured sensor sensitivity and the modeling result is only about 0.33%.