Application of Fiber Bragg grating for determining positions of gas absorption lines

Abstract

Fiber Bragg grating (FBG) is used as a wavelength reference device to calibrate the position of gas absorption peak in the intracavity absorption gas sensor (ICAGS) based on erbium-doped fiberring laser. This system can detect both the reflectance spectrum of FBGs and absorption spectrum of measured gas during a single wavelength sweeping process by linearly varying the driving voltage of optic filter. The voltages corresponding to center wavelength positions of four FBGs in the spectrum are determined through Gaussian peak fitting. Then, the wavelengths of gas absorption lines are deduced from the correspondence between driving voltage and wavelength obtained by quadratic curve fitting. The maximum error of wavelength of acetylene absorption lines between experimental results and those from HITRAN database is 0.106 nm and the resolving accuracy of two adjacent absorption lines is about 93.593%. By using this method, ICAGS can theoretically recognize the measured gas type and monitor multi-gas components.

Keywords

fiber Bragg grating / gas absorption / erbium-doped fiber / Gaussian fitting

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