[Signal analysis and spectrum distortion correction for tunable diode laser absorption spectroscopy system]

Area of Science:

• Optical Spectroscopy
• Laser Physics
• Analytical Chemistry

Context:

• Tunable diode laser absorption spectroscopy (TDLAS) is a powerful technique for trace gas sensing.
• Laser intensity modulation can induce spectrum distortion, affecting measurement accuracy.
• Existing TDLAS systems face challenges with wide modulation amplitudes and dynamic range requirements.

Purpose:

• To investigate spectrum distortion in TDLAS caused by laser intensity modulation using Fourier analysis.
• To propose and validate a synchronous amplitude modulation suppression method using a variable optical attenuator.
• To reduce the dynamic range requirements of TDLAS system components.

Summary:

• A Fourier analysis method was used to study spectrum distortion in TDLAS systems with wide modulation amplitudes.
• A novel method employing a variable optical attenuator was developed to suppress laser intensity modulation.
• Experimental validation using CO2 gas demonstrated a 92% improvement in spectrum distortion and reduced residual modulation to -0.1%.

Impact:

• The proposed method effectively corrects spectrum distortion, enhancing the accuracy of TDLAS trace gas analysis.
• Reduced dynamic range requirements lower the cost and complexity of TDLAS systems.
• This technique is suitable for online trace gas monitoring in various industrial process applications.