Simultaneous Temperature and Strain Sensing Based on M-Shaped Single Mode Fiber

Abstract

We propose a novel M-shaped single mode fiber (M-SMF) sensor based on stimulated Brillouin scattering of higher-order acoustic modes for simultaneous temperature and strain measurement. Numerical investigation of longitudinal acoustic modes in the M-SMF shows that multi-peak Brillouin spectrum in M-SMF is contributed by the couplings between the LP01 optical mode and multiple acoustic modes. The Brillouin characteristics in the M-SMF are compared with those of standard single mode fiber. Utilizing the multi-peak feature of Brillouin gain spectrum, sensing characteristics of the M-SMF under different temperature and strain conditions were studied. Thanks to the widely spaced $L_{01}$ and $L_{02}$ acoustic mode peaks in the Brillouin spectrum of M-SMF, the proposed fiber enables discriminative sensing of temperature and strain at an accuracy of 0.47 °C and $12.3~{\mu \varepsilon }$ , respectively.