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.

The paper presents the properties of a strain sensor, which was made using the micro hole collapse method and operates in the configuration of a Mach-Zehnder modal interferometer with a PM-1550-01 polarization maintaining photonic crystal fibre. The sensor’s transfer curve was determined analytically. Its strain sensitivity, determined from measurements, decreases slightly with increasing wavelength and is in a range from −2.01 to −2.23 pm/µε in the wavelength range 1520–1580 nm. Based on the Fourier analysis of the wavelength spectrum of the constructed sensor, the difference of the group refractive indices of the core and the cladding of the photonic crystal fibre was determined, which are in a range from 7.45·10−3 to 1.01·10−2. The temperature sensitivity of the sensor, determined on the basis of measurements performed in a range from 23 to 60◦C, is positive and equals 5.9 pm/K.