Journal: Scientific Reports
Article Title: A new gas detection technique through cross-correlation with a complex aperiodic FBG
doi: 10.1038/s41598-024-59841-7
Figure Lengend Snippet: ( a ) Transmission spectrum of the complex FBG (red) compared with the absorption spectra of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_2H_2$$\end{document} C 2 H 2 (black), HCN (blue), CO (green). ( b ) Absorption spectrum of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_2H_2$$\end{document} C 2 H 2 (black), compared with the transmission of the complex FBG (red). ( c ) Absorption spectrum of HCN (blue), compared with the transmission of the complex FBG (red).
Article Snippet: A fibre-coupled benchtop Superluminescent Diode (SLD; ThorLabs model S5FC1005P with centre \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda$$\end{document} λ 1550 nm, bandwidth 50 nm, power 22 mW, T: 22.5 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ$$\end{document} ∘ C) was used as the light source for the experiment.
Techniques: Transmission Assay
![( a ) Custom design of the aperiodic FBG as represented by amplitude ( <t>\documentclass[12pt]{minimal}</t> \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\kappa$$\end{document} κ ) and phase ( \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\theta$$\end{document} θ ) along the axis of the fibre. ( b ) Schematic representation of the index modulation and phase variation in the core of a complex aperiodic FBG optical fiber. ( c ) Comparison of the complex FBG transmission response (red) with the p-band absorption features of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_2H_2$$\end{document} C 2 H 2 (black) which it was designed to mimic. ( d ) Reflection spectrum of the complex FBG filter.](https://pub-med-central-images-cdn.bioz.com/pub_med_central_ids_ending_with_6915/pmc11576915/pmc11576915__41598_2024_59841_Fig1_HTML.jpg)
![( a ) Schematic of the experimental setup. Transmitted (red) and reflected (blue) light paths are shown. The fibre is stretched using clamps and a motor to precisely control the strain. ( b ) The wavelength of a single peak from the complex FBG spectrum as a product of applied strain. The observed shift exhibits a direct proportionality to the applied strain, underscoring a consistent correlation between the strain and the wavelength alteration. ( c ) Example trace using a single \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_2H_2$$\end{document} C 2 H 2 gas cell showing the intensity of reflected light (blue) as the tension applied (red) to the FBG is modulated. This shows the total intensity of reflected light as stretching occurs.](https://pub-med-central-images-cdn.bioz.com/pub_med_central_ids_ending_with_6915/pmc11576915/pmc11576915__41598_2024_59841_Fig2_HTML.jpg)
![( a ) Averaged and normalised sweeps for three different gas cell concentrations of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_2H_2$$\end{document} C 2 H 2 . Increasing concentration correlates with lower minima for each gas chamber. ( b ) OCS signals for \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_2H_2$$\end{document} C 2 H 2 compared to mixed gas configurations that also include CO and HCN as ‘contaminants’. The shaded regions in both graphs represent the standard deviation ( \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sigma$$\end{document} σ ) of the averaged sweeps. ( c ) Simulation results for \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_2H_2$$\end{document} C 2 H 2 and contaminating gases, including those in mixed gas environments. The simulations involving HCN and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_2H_2$$\end{document} C 2 H 2 exhibit features in the interline period that closely mirror those observed in the experimental data presented in the previous panel.](https://pub-med-central-images-cdn.bioz.com/pub_med_central_ids_ending_with_6915/pmc11576915/pmc11576915__41598_2024_59841_Fig3_HTML.jpg)
![( a ) Transmission spectrum of the complex FBG (red) compared with the absorption spectra of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_2H_2$$\end{document} C 2 H 2 (black), HCN (blue), CO (green). ( b ) Absorption spectrum of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$C_2H_2$$\end{document} C 2 H 2 (black), compared with the transmission of the complex FBG (red). ( c ) Absorption spectrum of HCN (blue), compared with the transmission of the complex FBG (red).](https://pub-med-central-images-cdn.bioz.com/pub_med_central_ids_ending_with_6915/pmc11576915/pmc11576915__41598_2024_59841_Fig4_HTML.jpg)