[OPTICAL REVIEW Vol. 18, No. 1 (2011) 93-95]
© 2011 The Japan Society of Applied Physics
Fiber-Optic Humidity Sensor Based on an Air-Gap Long Period Fiber Grating
Ming-Yue FU*, Guei-Ru LIN1, Wen-Fung LIU2, and ChengWen WU3
Department of Avionics Engineering, Air Force Academy, Kaohsiung 820, Taiwan, R.O.C.
1Ph. D. Program in Electrical and Communications Engineering, Feng-Chia University, Taichung 40724, Taiwan, R.O.C.
2Department of Electrical Engineering, Feng-Chia University, Taichung 40724, Taiwan, R.O.C.
3Department of Photonics, Feng-Chia University, Taichung 40724, Taiwan, R.O.C.
(Received May 31, 2010; Accepted November 17, 2010)
In this paper, we propose a novel high-sensitivity fiber-optic humidity sensor based on a calcium chloride thin film to be coated on an air-gap long-period grating fabricated (AG-LPG) by combining the fiber side-polishing and fiber etching methods. When the surrounding refractive index of the air-gap long-period grating is changed by a change in humidity, the grating resonant wavelength is considered varied. Experimental results indicate that humidity can be detected by this sensing mechanism and has a high sensitivity of about 1.36 nm/1%RH.
Key words: fiber side polishing, fiber etching, air gap, long period grating
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