Spectroscopic real-time monitoring of methane and acetylene using noise-like pulse ultrafast dynamics in supercontinuum generation

The implementation of a spectroscopic system for the detection and real time monitoring of methane (CH₄) and acetylene (C₂H₂) is presented, using an all-fiber supercontinuum source generated by noise-like pulses (NLP) tunable by polarization. The generated spectrum ranges from 1500 nm to 1680 nm and has an output power of ∼3.4 mW. Experimental results show that the registered absorption peaks of C₂H₂ have a maximal depth of approximately 30.8 <i>dB</i>, and 32 intense lines in the R and P branches, whereas the CH₄ peaks have a maximum depth of approximately 14.5 <i>dB</i>, and 18 intense lines. Besides, it is shown that small adjustments in the system polarization state significantly modify the SC spectral profile, affecting the visibility of the absorption signals, and allowing for adjusting the system sensitivity. Finally, the experimental spectra were validated through their comparison with the HITRAN database simulations. To the best of our knowledge, this is the first experimental demonstration of a system for real-time monitoring of two gases based on an SC source generated by NLPs. The proposed configuration represents a robust and simple solution for the practical detection of multiple gaseous species in environmental or industrial environments.