A micro MMF layer embedded in LPFG for simultaneous measurement of curvature and temperature

A micro multimode fiber (MMF) layer embedded in long period fiber grating (ME-LPFG) has been developed and experimentally investigated for the simultaneous measurement of curvature and temperature. The LPFG is written by using high-frequency CO2 laser pulses. The transmission spectrum of the novel LPFG can show the wavelength shift and splitting characteristics relative to the original LPFG. The wavelengths of the two resonant peak changes are used to monitor the variations of the curvature and temperature due to different responses. The experimental results show that the curvature sensitivities of the two peaks are -7.056 nm/m(-1) and -21.080 nm/m(-1), respectively. The curvature sensitivity is bigger than that of the common LPFG. And the temperature sensitivities of the two peaks reach 60 pm/degrees C and 58 pm/degrees C, respectively. Therefore the ME-LPFG has the potential to measure the curvature and temperature simultaneously with the resolutions of 4.7x10(-5) m(-1) and 0.3 degrees C.