Multi-component gases are a typical form of practical field measurement environment, and the issue of cross-interference between multi-component gases can significantly impact the precision of detection results. Multi-component gas detection is a promising use of Tunable Diode Laser Absorption Spectroscopy (TDLAS), an optical technology with wavelength tunability, high selectivity, and multi-component detection capabilities. This paper describes the reasons and correction methods for the cross-interference phenomenon of multi-component gases, introduces several multi-component gas detection algorithms based on TDLAS technology, analyzes the advantages and disadvantages of the algorithms as well as their scope of application, and aims to provide a reference for the cross-interference correction technology of multi-component gas detection.
KEYWORDS: Beam path, Signal detection, Light absorption, Signal generators, Thermoelasticity, Sensors, Optical gas detection, Modulation, Gas sensors, Fiber lasers
In recent years, gas sensors are widely used in military and civilian fields. Light-Induced Thermoelastic Spectroscopy (LITES) plays an important role in trace gas sensing. This paper focuses on our recent work to improve the performance of the LITES gas detection system. Firstly, a LITES gas detection system based on a novel QTF-self-difference technique was proposed. The Distributed Feedback Laser Diode (DFB-LD) was internally driven by a low-frequency scanning signal and externally modulated by a high-frequency modulated signal using an Acousto-Optic Modulator (AOM). The output laser was divided into two laser beams by a fiber coupler and irradiated from both sides of the QTF, and the signal was measured using the light-induced thermoelastic properties of the QTF. The results showed that the system can reduce the noise of the LITES system and has a good linear response. Secondly, a long-path LITES gas sensor using a high-power Q-switched fiber laser was reported. The LITES gas detection system signal was enhanced by increasing the laser power and absorption optical path. The sensor achieved a Minimum Detection Limit (MDL) of 6.1 ppb at the integration time of 48 s. Finally, a comprehensive dual-spectroscopy detection technique based on LITES and Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) using a quartz tuning fork was demonstrated. The system utilized a dual-spectrum detection structure to enhance the detection sensitivity. The system was tested for C2H2, and the results showed that the system has superior detection performance compared to conventional detection systems.
A methane leakage monitoring system based on light-induced thermoelastic spectroscopy (LITES) is proposed in this manuscript. We use our methane leakage monitoring system for methane detection at the wavelength of 1650.961 nm. This system has a minimum detection limit of 62.8 ppm·m and a good linear response (R-square = 0.997). We also simulated methane leakage, and the results show that our system has the ability to monitor methane leakage.
Quartz enhanced photoacoustic spectroscopy (QEPAS) is a high performance trace gas detection technique that plays an important role in food safety, pollution monitoring and breath analysis applications. It is well known that the sensitivity of QEPAS gas detection system is proportional to excitation laser power and thus the performance of QEPAS-based sensors can benefit from the high output power levels achieved as a result of technology developments by the high power laser. This paper mainly introduces three kinds of QEPAS gas sensor based on fiber-ring laser.
The laser methane remote sensor based on tunable diode laser absorption spectroscopy (TDLAS) technology uses open optical path instead of traditional absorption chamber to achieve zero-contact long-distance gas detection. It has the advantages of high measurement accuracy, fast response speed and large detection range. It can be applied to gas leakage monitoring places such as stations of urban natural gas pipeline network, transportation pipelines, underground comprehensive pipe corridors and industrial oil and gas drilling and production safety fields. This paper mainly introduces two kinds of laser methane remote sensor based on TDLAS, which are fixed reflection laser methane telemetry and echo reflection laser methane telemetry.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.