Development of an intra-cavity gas detection system based on L-band erbium-doped fiber ring laser

In this study, a gas detection system based on intra-cavity absorption spectroscopy technique and L-band erbium-doped fiber ring laser is constructed. With a fiber Fabry–Perot tunable filter used for spectral scanning, the system can acquire multiple absorption lines of the detected gas. In order to improve the detection accuracy, reference wavelengths are introduced to calibrate the nonlinearity of the filter, and polynomial fitting is proposed to compensate the impact of temperature variation on gas absorption. When the system is applied to detect the concentration of CO2, the absolute error is less than 400 ppm, corresponding to a relative error under 0.52%. The monitoring error of absorption wavelength is no more than 30 pm. The system also has the ability to detect other gas species which have absorption lines in L-band.