A novel type multimode fiber optic Bragg grating (MM-FBG) sensorfor strain and temperature sensing has been developed for apower-by-light hydraulic valve monitoring system. The Bragg gratingsensor was fabricated by the holographic method in 62/125 μmgraded-index silica multimode fiber. The sensor has reflectivity ofapproximately 35% at 835 nm of peak wavelength. The experiment of strainsensing has been tested by apply axial strains from zero to 1000με and the temperature sensing test has been done fortemperatures from -40° C and 80° C. The strain sensitivity of theMM-FBG is 0.55 pm/με and the average temperature sensitivity isapproximately 6 pm/° C
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