Simultaneous measurement of temperature and strain or temperature and curvature based on an optical fiber Mach-Zehnder interferometer

A compact optical fiber Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated for simultaneous measurement of temperature and strain or temperature and curvature. This device consists of input single mode fiber (SMF), a fiber Bragg grating (FBG), a short section of multimode fiber (MMF) and output SMF, of which the FBG is offset spliced with upstream input SMF. The high-order cladding modes can be excited at the core offset plane and then be recoupled to the output SMF through the MMF. The interference dip of 1563 nm is selected to demonstrate the interferometer's response to strain and curvature, and the Bragg peak is used to monitor temperature variation. The experimental results demonstrate that the strain and curvature sensitivities of the proposed MZI are −0.12 pm/με and −164 pm/m−1, and the temperature sensitivities of FBG and MZI are 9 pm/°C and 52 pm/°C, respectively. The simultaneous measurement of temperature and strain or temperature and curvature can be realized through the demodulation matrixes.