A Method for Real-Time Monitoring of Inherent System Loss Designed for FLRDS-Based Gas Sensors

An important factor restricting the development of fiber loop ring-down spectroscopy (FLRDS) is that real-time continuous monitoring of the inherent system loss is inconvenient and time-consuming. However, the inherent system loss will vary across environments. To ensure measurement accuracy, real-time monitoring is essential. This paper proposes a method for real-time monitoring of the inherent system loss to improve the accuracy of FLRDS-based gas sensors. A precise dual-wavelength tuning of the laser diode can be achieved by changing the injection current, in which the emission wavelength outside the absorption region can be used to acquire the inherent system loss value fast and conveniently. The advantage of this method has been verified by testing the acetylene concentration of a calibration gas with 1% acetylene. The average measurement error can be decreased from 1.393% to 0.037% through detection and correction the inherent system loss.