Frequency division multiplexing and wavelength stabilized 2f/1f wavelength modulation spectroscopy for simultaneous...

Area of Science:

• Environmental Science
• Analytical Chemistry
• Spectroscopy

Background:

• Accurate monitoring of atmospheric trace gases like methane (CH4) and carbon dioxide (CO2) is crucial for climate change research and environmental management.
• Existing sensor technologies often face challenges with sensitivity, precision, and simultaneous detection of multiple gases.

Purpose of the Study:

• To develop a highly sensitive and precise near-infrared (NIR) dual-gas sensor for simultaneous atmospheric detection of CH4 and CO2.
• To demonstrate the long-term stability and effectiveness of the developed sensor system for real-time environmental monitoring.

Main Methods:

• Utilized wavelength modulation spectroscopy with 2f/1f (WMS-2f/1f) detection to eliminate laser light intensity fluctuations.
• Implemented a proportion integration differentiation (PID) algorithm for laser wavelength locking to suppress spectral drift.
• Employed frequency division multiplexing (FDM) with two fiber-coupled DFB diode lasers (1653.7 nm for CH4, 1579.6 nm for CO2) for simultaneous measurement and crosstalk mitigation.

Main Results:

• Achieved a detection sensitivity of 0.1 ppm for CH4 and 2.27 ppm for CO2 with a 1-second average time.
• Optimized integration times yielded improved sensitivities of 18 ppb for CH4 and 0.3 ppm for CO2.
• Demonstrated long-term stability through real-time ambient atmospheric trace gas measurements.

Conclusions:

• The developed NIR dual-gas sensor provides a robust platform for high-precision, simultaneous monitoring of atmospheric CH4 and CO2.
• The combination of WMS-2f/1f, PID algorithm, and FDM techniques effectively addresses sensitivity, stability, and crosstalk challenges.
• This sensor technology holds significant potential for environmental monitoring, climate studies, and greenhouse gas management.