{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,16]],"date-time":"2026-06-16T21:03:06Z","timestamp":1781643786067,"version":"3.54.5"},"reference-count":85,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2017,11,24]],"date-time":"2017-11-24T00:00:00Z","timestamp":1511481600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The fast and reliable analysis of the natural gas composition requires the simultaneous quantification of numerous gaseous components. To this end, fiber-enhanced Raman spectroscopy is a powerful tool to detect most components in a single measurement using a single laser source. However, practical issues such as detection limit, gas exchange time and background Raman signals from the fiber material still pose obstacles to utilizing the scheme in real-world settings. This paper compares the performance of two types of hollow-core photonic crystal fiber (PCF), namely photonic bandgap PCF and kagom\u00e9-style PCF, and assesses their potential for online determination of the Wobbe index. In contrast to bandgap PCF, kagom\u00e9-PCF allows for reliable detection of Raman-scattered photons even below 1200 cm\u22121, which in turn enables fast and comprehensive assessment of the natural gas quality of arbitrary mixtures.<\/jats:p>","DOI":"10.3390\/s17122714","type":"journal-article","created":{"date-parts":[[2017,11,24]],"date-time":"2017-11-24T06:39:25Z","timestamp":1511505565000},"page":"2714","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":36,"title":["Monitoring the Wobbe Index of Natural Gas Using Fiber-Enhanced Raman Spectroscopy"],"prefix":"10.3390","volume":"17","author":[{"given":"Vincenz","family":"Sandfort","sequence":"first","affiliation":[{"name":"Laboratory for Gas Sensors, Department of Microsystems Engineering\u2013IMTEK, University of Freiburg, Georges-K\u00f6hler-Allee 102, 79110 Freiburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Barbara","family":"Trabold","sequence":"additional","affiliation":[{"name":"Max Planck Institute for the Science of Light, Staudtstra\u00dfe 2, 91058 Erlangen, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amir","family":"Abdolvand","sequence":"additional","affiliation":[{"name":"Max Planck Institute for the Science of Light, Staudtstra\u00dfe 2, 91058 Erlangen, Germany"},{"name":"School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Ave, Singapore 639798, Singapore"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Carsten","family":"Bolwien","sequence":"additional","affiliation":[{"name":"Fraunhofer Institute for Physical Measurement Techniques IPM, Heidenhofstra\u00dfe 8, 79110 Freiburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Philip","family":"Russell","sequence":"additional","affiliation":[{"name":"Max Planck Institute for the Science of Light, Staudtstra\u00dfe 2, 91058 Erlangen, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"J\u00fcrgen","family":"W\u00f6llenstein","sequence":"additional","affiliation":[{"name":"Laboratory for Gas Sensors, Department of Microsystems Engineering\u2013IMTEK, University of Freiburg, Georges-K\u00f6hler-Allee 102, 79110 Freiburg, Germany"},{"name":"Fraunhofer Institute for Physical Measurement Techniques IPM, Heidenhofstra\u00dfe 8, 79110 Freiburg, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2109-1936","authenticated-orcid":false,"given":"Stefan","family":"Palzer","sequence":"additional","affiliation":[{"name":"Department of Computer Science, Universidad Aut\u00f3noma de Madrid, Francisco Tom\u00e1s y Valiente 11, 28049 Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2017,11,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1088\/0022-3735\/22\/2\/009","article-title":"Rapid determination of the Wobbe index of natural gas","volume":"22","author":"Florisson","year":"1989","journal-title":"J. Phys. E"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2535","DOI":"10.1016\/j.fuel.2007.02.024","article-title":"A combustionless determination method for combustion properties of natural gases","volume":"86","author":"Loubar","year":"2007","journal-title":"Fuel"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1235","DOI":"10.1016\/j.ijhydene.2006.07.024","article-title":"From natural gas to hydrogen via the Wobbe index: The role of standardized gateways in sustainable infrastructure transitions","volume":"32","author":"Egyedi","year":"2007","journal-title":"Int. J. Hydrogen Energy"},{"key":"ref_4","first-page":"962","article-title":"Interchangeability of Gaseous Fuels\u2014The Importance of the Wobbe-Index","volume":"95","author":"Klimstra","year":"1986","journal-title":"Exp. Fluids"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Griffiths, P.R., and de Haseth, J.A. (2007). Fourier Transform Infrared Spectrometry, John Wiley & Sons, Inc.","DOI":"10.1002\/047010631X"},{"key":"ref_6","unstructured":"Gremlich, H.-U. (2008). Infrared and Raman Spectroscopy. Handbook of Analytical Techniques, Wiley-VCH Verlag GmbH."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"58","DOI":"10.1016\/0165-9936(87)87024-3","article-title":"Gas chromatography\u2014Fourier transform infrared spectroscopy\u2014Mass spectrometry. A powerful tool for component identification in complex organic mixtures","volume":"6","author":"Demirgian","year":"1987","journal-title":"TrAC Trends Anal. Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1153","DOI":"10.5194\/amt-6-1153-2013","article-title":"Assessment of a multi-species in situ FTIR for precise atmospheric greenhouse gas observations","volume":"6","author":"Hammer","year":"2013","journal-title":"Atmos. Meas. Tech."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Grob, R.L., and Barry, E.F. (2004). Modern Practice of Gas Chromatography, John Wiley & Sons, Inc.. [4th ed.].","DOI":"10.1002\/0471651141"},{"key":"ref_10","unstructured":"Eiceman, G.A. (2006). Instrumentation of Gas Chromatography. Encyclopedia of Analytical Chemistry, John Wiley & Sons, Ltd."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Sparkman, O.D., Penton, Z., and Kitson, F.G. (2011). Gas Chromatography and Mass Spectrometry: A Practical Guide, Academic Press.","DOI":"10.1016\/B978-0-12-373628-4.00002-2"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1287","DOI":"10.1002\/jms.388","article-title":"Analyses of gas composition in vacuum systems by mass spectrometry","volume":"37","author":"Repa","year":"2002","journal-title":"J. Mass Spectrom."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1465","DOI":"10.1021\/ac50033a022","article-title":"Isotope-ratio-monitoring gas chromatography-mass spectrometry","volume":"50","author":"Matthews","year":"1978","journal-title":"Anal. Chem."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2088","DOI":"10.3390\/s100302088","article-title":"Metal oxide gas sensors: Sensitivity and influencing factors","volume":"10","author":"Wang","year":"2010","journal-title":"Sensors"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1016\/S0021-9673(98)00706-7","article-title":"Aspects of the mechanism of the flame ionization detector","volume":"842","author":"Holm","year":"1999","journal-title":"J. Chromatogr. A"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"012004","DOI":"10.1088\/0957-0233\/24\/1\/012004","article-title":"Optical gas sensing: A review","volume":"24","author":"Hodgkinson","year":"2013","journal-title":"Meas. Sci. Technol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"142","DOI":"10.1364\/OL.6.000142","article-title":"Detection of atomic oxygen by intracavity spectroscopy","volume":"6","author":"Harris","year":"1981","journal-title":"Opt. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Wartewig, S., Schorn, C., and Bigler, P. (2003). IR and Raman Spectroscopy, Wiley-VCH Verlag GmbH & Co., KGaA.","DOI":"10.1002\/3527601635"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2889","DOI":"10.1109\/JSEN.2017.2682638","article-title":"Miniature low-cost carbon dioxide sensor for mobile devices","volume":"17","author":"Scholz","year":"2017","journal-title":"IEEE Sens. J."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"885","DOI":"10.1016\/j.snb.2016.03.022","article-title":"Low-cost gas sensing system for the reliable and precise measurement of methane, carbon dioxide and hydrogen sulfide in natural gas and biomethane","volume":"236","author":"Knobelspies","year":"2016","journal-title":"Sens. Actuators B Chem."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"4424","DOI":"10.1364\/AO.48.004424","article-title":"Improved sensitivity gas detection by spontaneous Raman scattering","volume":"48","author":"Buric","year":"2009","journal-title":"Appl. Opt."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"5278","DOI":"10.1021\/ac404162w","article-title":"Fiber-Enhanced Raman Multigas Spectroscopy: A Versatile Tool for Environmental Gas Sensing and Breath Analysis","volume":"86","author":"Hanf","year":"2014","journal-title":"Anal. Chem."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1007\/BF01618368","article-title":"Can the Raman scattering analyzer compete with mass spectrometers: An affirmative reply","volume":"5","author":"Westenskow","year":"1989","journal-title":"J. Clin. Monit."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1007\/BF02851168","article-title":"Dedicated monitoring of anesthetic and respiratory gases By Raman scattering","volume":"2","author":"Wagenen","year":"1986","journal-title":"J. Clin. Monit."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"501","DOI":"10.1038\/121501c0","article-title":"A New Type of Secondary Radiation","volume":"121","author":"Raman","year":"1928","journal-title":"Nature"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Zoubir, A. (2012). Raman Imaging, Springer.","DOI":"10.1007\/978-3-642-28252-2"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"253","DOI":"10.1016\/0360-1285(79)90011-X","article-title":"Combustion diagnostics by laser Raman and fluorescence techniques","volume":"5","author":"Eckbreth","year":"1979","journal-title":"Prog. Energy Combust. Sci."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/0360-1285(77)90007-7","article-title":"The use of laser Raman diagnostics in flow fields and combustion","volume":"3","author":"Lederman","year":"1977","journal-title":"Prog. Energy Combust. Sci."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1372","DOI":"10.1364\/AO.39.001372","article-title":"Atmospheric temperature profiling in the presence of clouds with a pure rotational Raman lidar by use of an interference-filter-based polychromator","volume":"39","author":"Behrendt","year":"2000","journal-title":"Appl. Opt."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"602","DOI":"10.1364\/AO.15.000602","article-title":"Laser radar measurements of atmospheric temperature profiles by use of Raman rotational backscatter","volume":"15","author":"Cooney","year":"1976","journal-title":"Appl. Opt."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1126\/science.169.3940.20","article-title":"Laser Raman Spectroscopy","volume":"169","author":"Mooradian","year":"1970","journal-title":"Science"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Demtro\u0308der, W. (2013). Laserspektroskopie 2. Experimentelle Techniken, Springer Spektrum. [6th ed.].","DOI":"10.1007\/978-3-642-21447-9"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Larkin, P. (2011). Infrared and Raman Spectroscopy: Principles and Spectral Interpretation, Elsevier.","DOI":"10.1016\/B978-0-12-386984-5.10002-3"},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Long, D.A. (2002). The Raman Effect: A Unified Treatment of the Theory of Raman Scattering by Molecules, John Wiley & Sons Ltd.","DOI":"10.1002\/0470845767"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"826","DOI":"10.2514\/3.49358","article-title":"Gas Concentration Measurement by Coherent Raman Anti-Stokes Scattering","volume":"12","author":"Regnier","year":"1974","journal-title":"AIAA J."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"253","DOI":"10.1366\/000370277774463625","article-title":"A Review of the Theory and Application of Coherent Anti-Stokes Raman Spectroscopy (CARS)","volume":"31","author":"Tolles","year":"1977","journal-title":"Appl. Spectrosc."},{"key":"ref_37","unstructured":"Schrader, B. (2008). Infrared and Raman Spectroscopy: Methods and Applications, Wiley-VCH Verlag GmbH."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"272","DOI":"10.1088\/1464-4266\/5\/3\/312","article-title":"On cavity modification of stimulated Raman scattering","volume":"5","author":"Matsko","year":"2003","journal-title":"J. Opt. B Quantum Semiclass. Opt."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"989","DOI":"10.1119\/1.1973774","article-title":"The Stimulated Raman Effect","volume":"35","author":"Bloembergen","year":"1967","journal-title":"Am. J. Phys."},{"key":"ref_40","unstructured":"(2017, October 26). Kaiser Optical Systems AirHeadTM Gas-Phase Raman Probe. Available online: http:\/\/www.kosi.com\/na_en\/products\/raman-spectroscopy\/raman-probes-sampling\/airhead-probe-head.php."},{"key":"ref_41","unstructured":"(2017, October 26). Kaiser Optical Systems RamanRxn4TM Gas-Phase Analyzer. Available online: http:\/\/www.kosi.com\/na_en\/products\/raman-spectroscopy\/raman-analyzers\/raman-rxn4-gas-phase-analyzer.php."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"9521","DOI":"10.1364\/AO.55.009521","article-title":"Multipass optical system for a Raman gas spectrometer","volume":"55","author":"Petrov","year":"2016","journal-title":"Appl. Opt."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"2004","DOI":"10.1364\/AO.16.002004","article-title":"Retroreflecting multipass cell for Raman scattering","volume":"16","author":"Hill","year":"1977","journal-title":"Appl. Opt."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"289","DOI":"10.1515\/teme-2015-0055","article-title":"Atemzyklusgenaues An\u00e4sthesiegas-Monitoring mit einer laserbasierten Raman-Sonde unter klinischen Bedingungen","volume":"83","author":"Seeger","year":"2016","journal-title":"TM Tech. Mess."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"546","DOI":"10.1515\/teme-2014-1050","article-title":"Laserbasierte On-line-Analyse von Biogasen mit einer Raman-Sonde","volume":"81","author":"Seeger","year":"2014","journal-title":"TM Tech. Mess."},{"key":"ref_46","first-page":"976","article-title":"Potentials of Raman based sensor system for an online analysis of human inhale and exhale","volume":"16","author":"Seeger","year":"2015","journal-title":"Sci. Tech. J. Inf. Technol. Mech. Opt."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"708","DOI":"10.1002\/jrs.4711","article-title":"Demonstration of a signal enhanced fast Raman sensor for multi-species gas analyses at a low pressure range for anesthesia monitoring","volume":"46","author":"Krischke","year":"2015","journal-title":"J. Raman Spectrosc."},{"key":"ref_48","first-page":"731608-1","article-title":"Raman Sensing of Fuel Gases Using a Reflective Coating Capillary Optical Fiber","volume":"7316","author":"Buric","year":"2009","journal-title":"Fiber Opt. Sens. Appl. VI"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"163","DOI":"10.1063\/1.88100","article-title":"cw Raman fiber amplifier","volume":"26","author":"Stone","year":"1975","journal-title":"Appl. Phys. Lett."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"553","DOI":"10.1366\/000370272774351813","article-title":"Modification of a Commercial Argon Ion Laser for Enhancement of Gas Phase Raman Scattering","volume":"26","author":"Neely","year":"1972","journal-title":"Appl. Spectrosc."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"7803","DOI":"10.1021\/acs.analchem.5b01462","article-title":"Cavity-Enhanced Raman Spectroscopy of Natural Gas with Optical Feedback cw-Diode Lasers","volume":"87","author":"Hippler","year":"2015","journal-title":"Anal. Chem."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"982","DOI":"10.1021\/ac503450y","article-title":"Fast and Highly Sensitive Fiber-Enhanced Raman Spectroscopic Monitoring of Molecular H 2 and CH 4 for Point-of-Care Diagnosis of Malabsorption Disorders in Exhaled Human Breath","volume":"87","author":"Hanf","year":"2015","journal-title":"Anal. Chem."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"2023","DOI":"10.1039\/C5AN02120K","article-title":"All-in-one: A versatile gas sensor based on fiber enhanced Raman spectroscopy for monitoring postharvest fruit conservation and ripening","volume":"141","author":"Jochum","year":"2016","journal-title":"Analyst"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"746","DOI":"10.1002\/cite.201500113","article-title":"Neue Methoden der laserbasierten Gasanalytik","volume":"88","author":"Lambrecht","year":"2016","journal-title":"Chem. Ing. Tech."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"1770","DOI":"10.1177\/0003702816644611","article-title":"Raman Gas Analyzer (RGA): Natural Gas Measurements","volume":"70","author":"Petrov","year":"2016","journal-title":"Appl. Spectrosc."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1016\/j.snb.2012.09.004","article-title":"High sensitivity gas sensing by Raman spectroscopy in photonic crystal fiber","volume":"176","author":"Yang","year":"2013","journal-title":"Sens. Actuators B Chem."},{"key":"ref_57","doi-asserted-by":"crossref","first-page":"2762","DOI":"10.1016\/j.enpol.2005.04.018","article-title":"Examining market power in the European natural gas market","volume":"34","author":"Egging","year":"2006","journal-title":"Energy Policy"},{"key":"ref_58","doi-asserted-by":"crossref","first-page":"869","DOI":"10.1016\/j.enpol.2006.01.013","article-title":"Prospects of the European gas market","volume":"35","author":"Johnsson","year":"2007","journal-title":"Energy Policy"},{"key":"ref_59","doi-asserted-by":"crossref","first-page":"480","DOI":"10.1016\/j.enpol.2015.12.016","article-title":"Market fundamentals, competition and natural-gas prices","volume":"94","author":"Hulshof","year":"2016","journal-title":"Energy Policy"},{"key":"ref_60","first-page":"544","article-title":"Development of natural gas qualities in Europe","volume":"152","author":"Altfeld","year":"2011","journal-title":"Gas Qual."},{"key":"ref_61","unstructured":"Abbott, D.J., Bowers, J.P., and James, S.R. (2012, January 17\u201318). The Impact of Natural Gas Composition Variations on the Operation of Gas Turbines for Power Generation. Proceedings of the 6th International Conference on the Future of Gas Turbine Technology, Brussels, Belgium."},{"key":"ref_62","doi-asserted-by":"crossref","first-page":"8731","DOI":"10.1364\/OE.15.008731","article-title":"Micro-channels machined in microstructured optical fibers by femtosecond laser","volume":"15","author":"Grivas","year":"2007","journal-title":"Opt. Express"},{"key":"ref_63","doi-asserted-by":"crossref","first-page":"6690","DOI":"10.1364\/OE.15.006690","article-title":"Photonic band-gap fiber gas cell fabricated using femtosecond micromachining","volume":"15","author":"Hensley","year":"2007","journal-title":"Opt. Express"},{"key":"ref_64","doi-asserted-by":"crossref","first-page":"4371","DOI":"10.1364\/OL.37.004371","article-title":"Kagome hollow-core photonic crystal fiber probe for Raman spectroscopy","volume":"37","author":"Ghenuche","year":"2012","journal-title":"Opt. Lett."},{"key":"ref_65","doi-asserted-by":"crossref","first-page":"12680","DOI":"10.1364\/OE.15.012680","article-title":"Models for guidance in kagome-structured hollow-core photonic crystal fibres","volume":"15","author":"Pearce","year":"2007","journal-title":"Opt. Express"},{"key":"ref_66","doi-asserted-by":"crossref","unstructured":"Kneer, J., Eberhardt, A., Walden, P., Ortiz P\u00e9rez, A., W\u00f6llenstein, J., and Palzer, S. (2014). Apparatus to characterize gas sensor response under real-world conditions in the lab. Rev. Sci. Instrum., 85.","DOI":"10.1063\/1.4878717"},{"key":"ref_67","unstructured":"ISO\/TC 193\/SC 1 Analysis of Natural Gas (2016). ISO 6976:2016: Natural Gas\u2014Calculation of Calorific Values, Density, Relative Density and Wobbe Index from Composition, ISO. [3rd ed.]."},{"key":"ref_68","doi-asserted-by":"crossref","unstructured":"Grote, K.-H., and Feldhusen, J. (2011). Dubbel: Taschenbuch fu\u0308r den Maschinenbau, Springer. [23rd ed.].","DOI":"10.1007\/978-3-642-17306-6"},{"key":"ref_69","doi-asserted-by":"crossref","unstructured":"Hahne, E. (2010). Technische Thermodynamik: Einfu\u0308hrung und Anwendung, Oldenbourg.","DOI":"10.1524\/9783486710908"},{"key":"ref_70","doi-asserted-by":"crossref","unstructured":"Cerbe, G., Lendt, B., Bru\u0308ggemann, K., Dehli, M., and Gro\u0308schl, F. (2017). Grundlagen der Gastechnik Gasbeschaffung\u2014Gasverteilung\u2014Gasverwendung, Hanser.","DOI":"10.1007\/978-3-446-44966-4"},{"key":"ref_71","doi-asserted-by":"crossref","first-page":"415","DOI":"10.1016\/0022-3697(70)90081-8","article-title":"Raman spectra of vitreous silica, germania and sodium silicate glasses","volume":"31","author":"Hass","year":"1970","journal-title":"J. Phys. Chem. Solids"},{"key":"ref_72","first-page":"772","article-title":"Hydroxyl sites in SiO2 glass: A note on infrared and Raman spectra","volume":"71","author":"McMillan","year":"1986","journal-title":"Am. Mineral."},{"key":"ref_73","doi-asserted-by":"crossref","first-page":"6383","DOI":"10.1103\/PhysRevB.60.6383","article-title":"Calculation of Raman spectra and vibrational properties of silicate glasses: Comparison between Na2Si4O9 and SiO2 glasses","volume":"60","author":"Zotov","year":"1999","journal-title":"Phys. Rev. B"},{"key":"ref_74","doi-asserted-by":"crossref","first-page":"1118","DOI":"10.1126\/science.1149091","article-title":"Generation and photonic guidance of multi-octave optical-frequency combs","volume":"318","author":"Couny","year":"2007","journal-title":"Science"},{"key":"ref_75","doi-asserted-by":"crossref","first-page":"85408","DOI":"10.1088\/0957-0233\/19\/8\/085408","article-title":"Design and characterization of a Raman-scattering-based sensor system for temporally resolved gas analysis and its application in a gas turbine power plant","volume":"19","author":"Kiefer","year":"2008","journal-title":"Meas. Sci. Technol."},{"key":"ref_76","doi-asserted-by":"crossref","first-page":"125104","DOI":"10.1063\/1.3521397","article-title":"Characterization of a fast gas analyzer based on Raman scattering for the analysis of synthesis gas","volume":"81","author":"Eichmann","year":"2010","journal-title":"Rev. Sci. Instrum."},{"key":"ref_77","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1364\/JOSA.63.000073","article-title":"Raman cross-section of some simple gases","volume":"63","author":"Fenner","year":"1973","journal-title":"J. Opt. Soc. Am."},{"key":"ref_78","unstructured":"Perry, R.H., Green, D.W., and Maloney, J.O. (2008). Perry\u2019s Chemical Engineer Handbook, McGraw-Hill. [8th ed.]."},{"key":"ref_79","unstructured":"Bruus, H. (2008). Theoretical Microfluidics, Oxford University Press."},{"key":"ref_80","doi-asserted-by":"crossref","first-page":"2790","DOI":"10.1364\/AO.47.002790","article-title":"Dynamics of gas flow in hollow core photonic bandgap fibers","volume":"47","author":"Henningsen","year":"2008","journal-title":"Appl. Opt."},{"key":"ref_81","doi-asserted-by":"crossref","first-page":"4604","DOI":"10.1364\/AO.49.004604","article-title":"Analytical modeling of the gas-filling dynamics in photonic crystal fibers","volume":"49","author":"Dicaire","year":"2010","journal-title":"Appl. Opt."},{"key":"ref_82","doi-asserted-by":"crossref","first-page":"2005","DOI":"10.1063\/1.2738185","article-title":"Liquid core photonic crystal fiber sensor based on surface enhanced Raman scattering","volume":"90","author":"Zhang","year":"2007","journal-title":"Appl. Phys. Lett."},{"key":"ref_83","doi-asserted-by":"crossref","first-page":"3736","DOI":"10.1364\/OL.39.003736","article-title":"Selective excitation of higher order modes in hollow-core PCF via prism-coupling","volume":"39","author":"Trabold","year":"2014","journal-title":"Opt. Lett."},{"key":"ref_84","first-page":"712A","article-title":"Limit of Detection A Closer Look at the IUPAC Definition","volume":"55","author":"Long","year":"1983","journal-title":"Anal. Chem."},{"key":"ref_85","doi-asserted-by":"crossref","unstructured":"McCreery, R.L. (2000). Raman Spectroscopy for Chemical Analysis, John Wiley & Sons.","DOI":"10.1002\/0471721646"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/12\/2714\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:51:06Z","timestamp":1760208666000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/12\/2714"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,11,24]]},"references-count":85,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2017,12]]}},"alternative-id":["s17122714"],"URL":"https:\/\/doi.org\/10.3390\/s17122714","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2017,11,24]]}}}