Multi-Parameter Sensing Using a Fiber Bragg Grating Inscribed in Dual-Mode Fiber

We propose a method for simultaneous measurement of strain, temperature, and surrounding refractive index (SRI) using a fiber Bragg grating (FBG) inscribed in dual mode fiber by femtosecond laser. This FBG not only possesses two Bragg resonances corresponding to LP
₀₁
and LP
₁₁
modes, respectively, but also shows many strong cladding mode resonances, which are sensitive to SRI. Due to the different responses, the strain, temperature, and SRI can be discriminated simultaneously by measuring the two Bragg resonance wavelengths and the normalized area of cladding mode resonances. The estimated resolutions of this FBG in measuring strain, temperature, and SRI are ±6.3 με, ±0.8 °C, and ±2.7 × 10
^-5
RIU, respectively.