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9 November 2005 Fiber Bragg grating multi-functional chemical sensor
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A promising new fiber optic sensor is under development that combines fiber Bragg gratings coated with polymer materials for sensitive and rapid detection and identification of chemical and/or biological agents. Volumetric expansion of the polymer coating transfers characteristic strain to the Bragg grating, modifying directly its grating period rather than sensing through a change of effective guide index of refraction. The optical interrogation of the sensor element utilizes a sensitive transmission spectroscopy technique with a balanced receiver that minimizes polarization and laser intensity noise problems. A compact, rugged, all-solid-state laser at 1550 nm is being adapted for rapid tuning between discrete preset locked wavelengths. To accompany use of this laser at these few discrete wavelengths, a sampled (superstructure) fiber Bragg grating is being designed using coupled mode theory. Hence, the need for a continuously tunable laser, often with moving mechanical optical elements, and its attendant reference etalon will be avoided entirely. This process exploits a novel vernier effect between the discrete laser wavelengths and the sampled grating responses to create 'signatures' for an artificial neural network. Therefore, the total spectral response pattern of strain can constitute a unique fingerprint used to identify and quantify chemical agents or biomarkers. The sensor is intended for applications requiring multi-functionality, sensitivity, speed, mobility and remote operability in vibrational, electromagnetic, and explosive environments.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Gregory B. Tait, Gary C. Tepper, Dmitry Pestov, and Patrick M. Boland "Fiber Bragg grating multi-functional chemical sensor", Proc. SPIE 5994, Chemical and Biological Sensors for Industrial and Environmental Security, 599407 (9 November 2005);

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