In order to solve the problem of cross sensitivity of temperature and strain in Fiber Bragg Grating (FBG) sensing, the response characteristics of temperature and strain in each mode of Few Mode Fiber (FMF)-FBG were studied in this paper. A four-mode FBG temperature and strain dual parameter sensor was also proposed.

The basic mode and a few higher modes can be transmitted simultaneously in the low-mode fiber, taking into account the advantages of low mode dispersion of Single Mode Fiber (SMF) and low nonlinearity of multi-mode fiber, which can be used for sensing multiple physical quantities at the same time. By analyzing the different optical power sensitivity of the LP₀₁ mode in the FMF-FBG at different temperatures, and considering the good linearity of wavelength, temperature and strain under this mode. Thus, the temperature and strain dual parameter sensing of FMF-FBG is realized.

The results show that the sensor can better solve the problem of cross sensitivity of temperature and strain.

Compared with SMF-FBG, the FMF-FBG has several reflection peaks of different modes at the same time, which can not only solve the cross-sensitivity problem of temperature and strain, but also greatly improve the accuracy and stability of sensing, which may have a good application prospect in the field of new type of sensing.