Optical-fiber sensor using tailored porous sol-gel fiber core

• Published in: IEEE sensors journal Vol. 4; no. 3; pp. 322 - 328
• Main Authors: Shiquan Tao, Winstead, C.B., Jindal, R., Singh, J.P.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-06-2004; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Chemical sensors; Chemical transducers; Coatings; Fibers; Humidity; Microstructure; Optical fiber sensors; Optical fiber testing; Optical fibers; Optical sensors; Optical surface waves; Sensors; Silicon compounds; Silicon dioxide; Sol gel process; Transducers
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2004.827274

A new concept in optical-fiber chemical sensors, the active fiber core optical sensor (AFCOS), is presented. In this sensor, the fiber core acts as a transducer. The sensitivity of an AFCOS sensor is compared with that of an active coating [evanescent wave (EW)] based optical-fiber sensor. Requirements for a fiber core to act as a chemical sensor are discussed. Novel techniques for making a porous sol-gel silica fiber, doping chemical reagents into the fiber, and constructing a chemical sensor using the porous fiber as a transducer have been developed. The microstructure of the fabricated sol-gel silica fiber and the effect of the fiber's microstructure on the capability of the porous sol-gel silica fiber for guiding light are discussed. A humidity sensor employing a CoCl/sub 2/-doped porous sol-gel fiber as a transducer has been constructed as an example. The test results for the humidity sensor verified a theoretical analysis indicating that an optical-fiber chemical sensor using an active fiber core as a transducer has a much higher sensitivity than that of an EW-based sensor.