Simultaneous Multi-Component Gas Detection Using Distributed Cavity-Enhanced Raman Spectroscopy with Band-Area Normalized Calibration

A distributed cavity-enhanced Raman spectroscopy system was developed for the simultaneous detection of H2, O2, N2, and CO2 in confined spaces and complex gas environments. The system adopts an external-host/distributed-detection-cavity configuration, in which laser excitation, cavity-enhanced detection, Raman signal collection, and spectral detection are functionally separated to improve deployment flexibility for remote in situ measurements. Multi-peak fitting was used to extract the spectral band areas of different gas components, and band-area normalization was introduced to reduce the influence of laser power fluctuations, fiber coupling variations, and cavity coupling changes on concentration retrieval. The results show that H2, O2, N2, and CO2 exhibit clearly distinguishable Raman peaks and good linear concentration responses. The fitting correlation coefficients for H2, O2, N2, and CO2 are 0.998, 0.997, 0.996, and 0.998, respectively, with RMSE values of 0.03%, 0.21%, 0.35%, and 0.06%. After normalization, the average relative errors are reduced to 1.6%, 1.5%, 1.4%, and 1.3%, while the maximum relative errors are reduced to 3.2%, 3.1%, 2.9%, and 2.7%, respectively. Continuous measurements yield RSD values of 1.5%, 0.90%, 0.56%, and 1.25%, demonstrating good simultaneous detection capability and quantitative stability. The proposed system provides a feasible approach for online multicomponent gas monitoring in confined and complex environments.