12 October 2007 Long period grating-based fiber-optic PH sensor for ocean monitoring
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Proceedings Volume 6770, Fiber Optic Sensors and Applications V; 677019 (2007); doi: 10.1117/12.742088
Event: Optics East, 2007, Boston, MA, United States
Abstract
A fiber-optic PH sensor is developed based-on the long period grating (LPG). The LPG is fabricated by using CO2 laser with a point-by-point technique. Then the grating portion is coated with PH sensitive hydrogel. The hydrogel, made of PVA/PAA, swells its volume in response to the PH change in the surrounding environment and results in a change in the refractive index. As a result, the LPG can response to the refractive index change in the coating by shifting its wavelength. Therefore, change in refractive index can be measured by tracking the wavelength shift using an optical spectrum analyzer (OSA). In this research, the LPG is dip-coated by the hydrogel. A chemostat is designed to simulate the marine environment. The PH in the chemostat is varied by controlling the CO2 concentration in the sea water. A PH resolution 0.046/nm using the OSA has been obtained. This sensor is designed to monitor the sea water PH change in a long term basis.
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Ke Wang, Denis Klimov, Zbigniew Kolber, "Long period grating-based fiber-optic PH sensor for ocean monitoring", Proc. SPIE 6770, Fiber Optic Sensors and Applications V, 677019 (12 October 2007); doi: 10.1117/12.742088; http://dx.doi.org/10.1117/12.742088
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KEYWORDS
Carbon monoxide

Fiber optics sensors

Refractive index

Sensors

Water

Gas lasers

Coating

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