Frequency-modulated continuous-wave multiplexed gas sensing based on optical frequency comb calibration

Abstract

Laser absorption spectroscopy has proven to be an effective approach for gas sensing, which plays an important role in the fields of military, industry, medicine and basic research. This paper presents a multiplexed gas sensing system based on optical frequency comb (OFC) calibrated frequency-modulated continuous-wave (FMCW) tuning nonlinearity. The system can be used for multi-parameter synchronous measurement of gas absorption spectrum and multiplexed optical path. Multi-channel parallel detection is realized by combining wavelength division multiplexing (WDM) and frequency division multiplexing (FDM) techniques. By introducing nonlinear optical crystals, broadband spectrum detection is simultaneously achieved over a bandwidth of hundreds of nanometers. An OFC with ultra-high frequency stability is used as the frequency calibration source, which guarantees the measurement accuracy. The test samples involve H¹³C¹⁴N, C₂H₂ and Rb vapor cells of varying densities and 5 parallel measurement experiments are designed. The results show that the measurement accuracies of spectral absorption line and the optical path are 150 MHz and 20 μm, respectively. The scheme offers the advantages of multiplexed, multi-parameter, wide spectrum and high resolution detection, which can realize the identification of multi-gas components and the high-precision inversion of absorption lines under different environments. The proposed sensor demonstrates great potential in the field of high-resolution absorption spectrum measurement for gas sensing applications.