Investigation of gas detection based on fiber laser intracavity absorption spectroscopy

Fiber laser intracavity gas sensor has advantages of high sensitivity and wide wavelength coverage. We present our recent research progress on intracavity gas sensor including the modular structure design and the general procedure of signal processing. The methods of wavelength-sweep-based multiline averaging and attenuator-based cavity loss increment are used to enhance the gas sensor's stability and sensitivity respectively. The standard deviation of acetylene concentration measurement is reduced by half using the proposed enhancement method and the improved intracavity concentration sensitivity is about 60 times larger than the single-pass external-cavity sensitivity.

I. Introduction

Fiber gas sensors have various applications in industrial process control and environmental monitoring [1]. They have characteristics of immunity to electromagnetic interference, low cost, high selectivity and flexible multiplexing ability [2]. Several detection techniques have been developed for fiber gas sensors in recent decades, including differential absorption, tunable diode laser spectroscopy, photoacoustic spectroscopy and cavity enhanced techniques [3]–[6]. Each technique has its own superiority in some specific aspects such as simple system configuration, narrow laser linewidth, high sensitivity or wide wavelength coverage.