1 March 2009 Seawater pH sensor based on the long period grating in a single-mode–multimode–single-mode structure
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Abstract
A pH sensor is developed based on the long-period grating (LPG) inscribed into a single-mode–multimode–single-mode (SMS) structure in order to measure the pH in seawater. The LPG is formed by using a focused CO2 laser at LPG's critical period (1 mm). The transmission characteristics are similar to that of a multimode fiber. However, the SMS structure has a higher sensitivity because mode coupling only happens between the fundamental mode and higher-order modes in the SMS structure. The pH-sensitive hydrogel is made by the thermal cross-link of poly vinyl alcohol and poly acrylic acid. This sensor has been utilized in seawater pH sensing in the range of 6–8. Experiments have confirmed that the sensor is sensitive and repeatable.
© (2009) Society of Photo-Optical Instrumentation Engineers (SPIE)
Ke Wang, Denis V. Klimov, Zbigniew Kolber, "Seawater pH sensor based on the long period grating in a single-mode–multimode–single-mode structure," Optical Engineering 48(3), 034401 (1 March 2009). https://doi.org/10.1117/1.3093625 . Submission:
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