Optical fiber Bragg grating based chemical sensor

In this paper the feasibility study of an optical fiber Bragg grating (FBG) based chemical sensor is presented. A previously developed FBG pressure sensor was modified by enveloping the grating regions with polymer sleeves. When in contact with different chemical solvents, the polymers react with different degrees of swelling which change the force exerted on the underlying FBG, modulating the grating period and subsequently shifting the Bragg wavelength. The characteristic rates of change of the Bragg wavelength can then be examined to identify the chemical being measured. Preliminary experimental results of measuring different chemicals with the FBG sensor are presented and discussed.