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

^*E-mail address: fumy@cc.cafa.edu.tw