Simultaneous Measurement of Temperature and Strain Based on Peak Power Changes and Wavelength Shift Using Only One Uniform Fiber Bragg Grating

Abstract

Many efforts have been devoted to simultaneous measurements of strain and temperature by FBG sensors and several improving techniques have been resulted and implemented on the measurement. Most of them are based on two or more FBGs configurations or a single non-uniform FBG implementation. We propose simultaneous measurement of temperature and strain based on peak power changes and Bragg wavelength shifts using only one uniform fiber Bragg grating (FBG). We placed a ramp with the angle of θ, similar to a tilted cantilever beam, on an assumptive structure and stuck a uniform FBG on it. When a uniform strain applied to a structure, the cantilever beam converts it to a non-uniform strain distribution along with itself and consequently the uniform FBG. By creating this non-uniform strain distribution, the peak power of the reflection spectrum of the FBG will be sensitive to strain changes. In addition, the Bragg wavelength shift will be sensitive to both temperature and strain parameters. According to our simulation, temperature sensitivity of 14.15 pm/℃ is obtained for FBG sensor without any changes in the peak power. The strain sensitivity of 0.7837 pm/µε, and a nonlinear sensitivity according to a quadratic function for peak power variation are also observed.