Development and Integration of a CO Detection System Based on Wavelength Modulation Spectroscopy Using Near-Infrared DFB Laser

Abstract

A wavelength modulation spectroscopy-(WMS-) based gas sensing system was established to measure concentration of carbon monoxide (CO) in the range 0-100%. The CO absorption line at 1563.06 nm was scanned with a tunable distributed feedback (DFB) laser, and two InGaAs photodiodes were applied to perform optic-electric conversion. Without using commercial instruments, essential electrical circuits were self-developed and integrated, including laser temperature controller, laser current driver, signal generator, and digital lock-in amplifier. The gas cell deployed in the system was fiber coupled with a total effective optical path length of 50 cm. The second-order harmonic signal was extracted, and experiments of gas detection were carried out to investigate the performance of the sensor, including detection repeatability, detection accuracy, response time, and limit of detection (LoD). Experiment results show that the sensor is reliable and has acceptable probing performance. The maximum relative detection error is less than 3.8%, suggesting good detection stability. Benefiting from the self-developed sensor, the whole CO detection system has small size, affordable expense, and application potential.

A Near-Infrared Trace CO2 Detection System Based on an 1,580 nm Tunable Diode Laser Using a Cascaded Integrator Comb (CIC) Filter-Assisted Wavelength Modulation Technique and a Digital Lock-in Amplifier

“…In the WMS scheme, a hybrid signal is applied to the DFB laser driver, which is composed of a low frequency sawtooth wave scanning signal and a high frequency sinusoidal modulation signal. In order to obtain the optimized WMS signals, we performed a theoretical simulation according to principle of WMS and carried out the experimental test in the laboratory to obtain the optimized parameters of frequency, amplification factor, phase, and baseline of the modulated signal [13][14][15]. A scanning frequency (5 Hz) of the sawtooth wave tuning signal was used in this system and the modulation frequency of sinusoidal modulation signal was 7.8 kHz.…”

A simulation process of tunable open path diode laser spectrometer to detect a carbon monoxide gas in NIR region

“…which are more than four orders of magnitude and two orders of magnitude weaker than the fundamental band, respectively Near-infrared CO sensors are inappropriate for most short path-length combustion systems due to low absorption strength and spectrum interference from carbon dioxide and water. J. Sebastian et al, [16] describe the use of a tunable diode laser-based sensor to detect carbon monoxide (CO) concentration under conditions comparable to those used in laboratory-scale studies to characterize the behavior of heavy crude oil during in situ burning (ISC).…”