Inunda detec sensor and inunda detec method

摘要

PROBLEM TO BE SOLVED: To detect water entry into an optical fiber with distinction from merely flexure.SOLUTION: A water entry detection sensor 10 comprises at least a hydrogen generation part 11 which is disposed in the vicinity of a water entry detection object optical fiber F, and is formed of a metal whose ionization tendency is higher than that of hydrogen, or a hydrogenated metal. The water entry detection sensor is configured to, using two reference wavelengths which generate no hydrogen absorption loss, and a detection wavelength which generates hydrogen absorption loss, measure optical loss of the optical fiber F at least twice with time interval, then measure a difference between them as a measured value of loss increment, then determine coefficients A, B of an estimation formula ΔL(λ)=Aexp(B/λ) of loss increment ΔL(λ) due to flexure to the wavelength λ, then substitute the detection wavelength as the wavelength λ to the estimation formula including the coefficients A, B to calculate an estimated value of loss increment in the detection wavelength, then compare the measured value of loss increment in the detection wavelength and the estimated value, and then determine occurrence of water entry into the optical fiber F when the measured value is larger than the estimated value.SELECTED DRAWING: Figure 1