[A Methane Detection System Using Distributed Feedback Laser at 1 654 nm]

Area of Science:

• Optical Engineering
• Spectroscopy
• Gas Sensing

Context:

• Methane (CH4) detection is crucial for environmental monitoring and industrial safety.
• Tunable diode laser absorption spectroscopy (TDLAS) offers high sensitivity and selectivity for gas analysis.
• Existing TDLAS systems require optimization for enhanced performance and stability.

Purpose:

• To experimentally demonstrate a methane detection system utilizing the TDLAS technique.
• To develop and test a stable laser temperature control and modulation module.
• To implement an orthogonal lock-in amplifier for precise harmonic signal extraction.

Summary:

• A TDLAS-based methane detection system was developed using a 1654 nm distributed feedback (DFB) laser, an open reflective probe, and InGaAs photodiodes.
• The system features a laser temperature control with fluctuations within ±0.02°C and an orthogonal lock-in amplifier capable of extracting 1f and 2f harmonic signals with minimal error.
• Experiments showed a linear correlation between harmonic signal amplitude and methane concentration (1-5%), confirming the system's functionality and suitability for trace gas detection.

Impact:

• The developed system provides a stable and accurate method for methane detection.
• The linear relationship observed enables precise quantification of methane concentrations.
• The modular design allows for adaptation to detect other trace gases by employing different DFB lasers.