This paper presents a fiber-optic sensor with intensity demodulation for simultaneous measurement of dynamic transverse force and axial strain. The sensor uses a Sagnac loop filter with a polarization-maintaining photonic crystal fiber (PM-PCF) that is subjected to a dynamic transverse force. The Sagnac loop filter is illuminated by the reflected beam froma uniform fiber-optic Bragg grating (FBG), which is subjected to an axial strain. This way, intensity demodulation is performed in the sensor, enabling it to measure two quantities simultaneously: the dynamic force and the strain. Experimental results show that the sensor achieves a sensitivity to the dynamic transverse force of 38.1 mV/N and a sensitivity to the axial strain of 0.527 mV/με, while the nonlinearity errorsare 4.9% for the dynamic force and 0.9% for the strain. The sensor exhibits low temperature sensitivity due to partial self-compensation of the temperature coefficients of the Sagnac loop filter with the polarization-maintaining photonic crystal fiber and the fiber Bragg grating.

This paper presents a simulation study of the simultaneous reconstruction of the non-smooth strain distribution of an optical fiber Bragg grating and its temperature, which is based on the reflection spectrum of the reflected beam of the grating. The transition matrix method was used to model the reflection spectrum of the grating, and the nonlinear Nelder-Mead optimization method was used to simultaneously reconstruct the strain distribution along the grating and its temperature. The results of simulations of simultaneous reconstruction of the strain profile and temperature indicate good accord with the strain profiles and temperature set. The reconstruction errors of the strain profiles are less than 1.2 percent and the temperature change errors are less than 0.2 percent, with a noise level of 5 percent.