Multi-component gas sensing and signal reception principles using a Raman spectroscopy fiber-optic sensor based on free-space optical coupling

Raman spectroscopy has demonstrated widespread applicability across diverse medical, environmental, and industrial sectors. This paper introduces a Raman spectroscopy fiber-optic sensor based on free-space optical coupling. Its simplified structure and high tolerance to alignment render it highly adaptable to various complex environments, thereby significantly expanding the on-site utility of Raman spectroscopy technology. Through a detailed analysis of Raman signal reception system principles, we have discovered the relationship between signal intensity and the diameter of the optical fiber responsible for signal reception. Leveraging this insight, we have implemented a fiber bundle to boost the system’s signal intensity by a factor of 2.5. This enhancement has enabled us to achieve a methane detection limit of 18 ppm with an exposure time of 60 s. These findings validate the enhanced performance of our Raman spectroscopy fiber-optic sensor probe and highlight its potential for various practical applications.