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Updated: Jul 2, 2026

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Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies
Published on: December 18, 2015
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An ML-Enhanced Laser-Based Methane Slip Sensor Using Wavelength Modulation Spectroscopy.
Mhanna Mhanna1, Jeremy Rochussen1, Patrick Kirchen1
1Department of Mechanical Engineering, University of British Columbia, 2054-6250 Applied Science Lane, Vancouver, British Columbia V6T 1Z4, Canada.
ACS Sensors
|January 15, 2025
Summary
A new laser sensor uses machine learning to accurately measure methane slip from natural gas engines. This innovation enables real-time monitoring for cleaner transport and environmental benefits.
Area of Science:
- Environmental Science
- Engineering
- Sensor Technology
Background:
- Natural gas (NG) is a sustainable transport fuel, but its greenhouse gas benefits depend on controlling methane slip.
- Existing methane slip measurement methods are often costly, require frequent calibration, and struggle with dynamic engine conditions.
- Accurate, real-time monitoring of methane (CH4) emissions is crucial for realizing the environmental advantages of NG vehicles.
Purpose of the Study:
- To develop a novel, machine learning-enhanced laser-based sensor for rapid, accurate, and calibration-free methane slip measurement in engine exhaust.
- To address the limitations of traditional methane slip monitoring techniques, including calibration needs, cost, and suitability for dynamic operations.
- To provide a robust sensor system for real-world application in natural gas engines to support emission reduction strategies.
Main Methods:
- Utilized wavelength modulation spectroscopy (WMS) with a distributed feedback (DFB) laser diode at 1.65 μm.
- Employed a machine learning approach, specifically Gaussian process regression (GPR), to invert WMS signals, reducing computational cost and noise uncertainty.
- Trained the GPR model on both simulated and measured WMS data for enhanced predictive accuracy.
Main Results:
- The machine learning-enhanced sensor achieved a mean absolute percent error (MAPE) of 0.24% during model training.
- Field testing on a natural gas marine vessel showed a mean absolute difference of 3.95% compared to reference Fourier transform infrared spectroscopy (FTIR) measurements.
- The system demonstrated rapid, accurate, and calibration-free methane (CH4) measurement capabilities in dynamic exhaust conditions.
Conclusions:
- The developed ML-enhanced WMS sensor represents a significant advancement for real-time methane slip monitoring in natural gas engines.
- This technology offers reduced computational demands and improved accuracy, facilitating engine optimization and regulatory compliance.
- Accurate methane slip data are essential for validating the environmental benefits of natural gas as a transport fuel and informing sustainable energy policies.

