Abstract

We describe a fiber-optic sensor capable of detecting high humidity. The device is constructed from standard telecommunications single-mode fiber and is compatible with deployment in a serial array, permitting interrogation by optical time-domain reflectometry for network monitoring. The sensors exhibit a reversible change in insertion loss between their dry (lossy) and humid (transmissive) states. The loss can be tailored to take any value; the current devices were designed to change by $\approx 2.5$ dB at a wavelength of 1.31 $\mathit{\mu }\mathrm{m}$. The sensors are simple to construct and are compatible with installation in an existing passive optical network. The transduction mechanism is based on the humidity-induced change in refractive index in a polymer overlay on a polished half-block single-mode fiber device.

© 1997 Optical Society of America

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