Stress applying TPMF based sensor for simultaneous temperature and strain measurement

Abstract

As the stress applying regions and the surrounding cladding of a thin polarization maintaining fiber (TPMF) have different thermal expansion coefficients and Poisson’s ratios, multi-mode interference in the TPMF has promising prospects in simultaneous temperature and strain measurement. We propose an in-fiber Mach-Zehnder sensor utilizing TPMF for simultaneous temperature and strain measurement. A section of TPMF is fusion spliced between two single mode fibers (SMFs) with an offset at one end to effectively excite cladding modes. Stress applying regions of the TPMF are sensitive to temperature and strain, which induces the effective refractive index (RI) variation of the cladding modes and the shift of the corresponding dip wavelength. The transmission spectra of the sensor under different temperatures and strains are monitored. Experimental results show that the temperature and strain sensitivities reach up to 91.84 pm/ºC and -2.37 pm/με. Simultaneous measurement is validated and the resolutions reach 0.41 ºC and 0.07 με. The maximum measurable strain is as large as 8000 με. The proposed sensor has the advantages of compactness, high sensitivity, low cost and ease of fabrication, making it a promising candidate in engineering applications.