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 ≈2.5 dB at a wavelength of 1.31 μm. 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
David C. Bownass, James S. Barton, and Julian D. C. Jones, "Serially multiplexed point sensor for the detection of high humidity in passive optical networks," Opt. Lett. 22, 346-348 (1997)