Water penetration sensing using wavelength tunable OTDR

A method for sensing penetration of water into optical cable using a wavelength-tunable optical time-domain reflectometer (OTDR) is proposed. The reflectivity at every Fabry-Perot connector gap contained in a monitoring fiber has periodic wavelength dependence. It is confirmed experimentally that water penetration into a connector gap results in a wavelength period change, the ratio of which coincides with the refractive index of water regardless of the size of the gap.<<ETX>>