Numerical and Experimental Investigation of a Fiber-Optic Sensor Consisting of a Fiber Bragg Grating in a Two-Mode Fiber for Simultaneous Sensing of Temperature and Strain

摘要

We investigate a fiber-optic sensor for the simultaneous measurement of temperature and strain. It consists of a fiber Bragg grating (FBG) inscribed into a short piece of two-mode fiber (TMF) that is spliced in-between a standard single mode fiber (SMF). By monitoring the spectral shift of the Bragg wavelength and the mode interference (MI) pattern, both physical quantities can be determined simultaneously. The sensor response to temperature and strain was investigated theoretically using a numerical sensor model and the results were verified experimentally. The measured temperature and strain sensitivities of the MI are found to be 175,3 pm/K and 3,24 pm/με, which is large compared to the FBG having sensitivities of 9,6 pm/K and 1,04 pm/με. The simultaneous measurement of temperature and strain was tested experimentally yielding promising results with maximum errors of measurement of 1,5 K and 82 με respectively.