{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T09:29:28Z","timestamp":1785403768803,"version":"3.56.0"},"reference-count":29,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2026,6,12]],"date-time":"2026-06-12T00:00:00Z","timestamp":1781222400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100022965","name":"MINCIENCIAS","doi-asserted-by":"crossref","award":["2021000100130"],"award-info":[{"award-number":["2021000100130"]}],"id":[{"id":"10.13039\/100022965","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/100022965","name":"MINCIENCIAS","doi-asserted-by":"crossref","award":["2019000100055"],"award-info":[{"award-number":["2019000100055"]}],"id":[{"id":"10.13039\/100022965","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/100022965","name":"MINCIENCIAS","doi-asserted-by":"crossref","award":["2019000100010"],"award-info":[{"award-number":["2019000100010"]}],"id":[{"id":"10.13039\/100022965","id-type":"DOI","asserted-by":"crossref"}]},{"award":["2021000100130"],"award-info":[{"award-number":["2021000100130"]}],"id":[{"id":"https:\/\/ror.org\/03fd5ne08","id-type":"ROR","asserted-by":"publisher"}]},{"award":["2019000100055"],"award-info":[{"award-number":["2019000100055"]}],"id":[{"id":"https:\/\/ror.org\/03fd5ne08","id-type":"ROR","asserted-by":"publisher"}]},{"award":["2019000100010"],"award-info":[{"award-number":["2019000100010"]}],"id":[{"id":"https:\/\/ror.org\/03fd5ne08","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Universidad Popular del Cesar"},{"id":[{"id":"https:\/\/ror.org\/05pzmdf74","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>We report an optical configuration to measure the concentration of ethanol (EtOH) using a light-guiding mechanism based on optical fibers in a Mach\u2013Zehnder-type interferometric configuration. The proposed configuration takes advantage of the high sensitivity of fiber optic interferometers, allowing variations in EtOH concentration to be detected from shifts in the interference patterns. The interferometric configuration was implemented using a single-mode optical fiber curved into a balloon shape. During the experiment, some spectral stability and hysteresis tests were performed on the device, obtaining good results. During the characterization stage for measuring EtOH concentration in the 40\u201371% v\/v range, performance parameters were evaluated, achieving EtOH concentration measurements in the 1500\u20131600 nm wavelength range. The sensitivity of the devices was evaluated in terms of the geometric parameters of the interferometric curved optical fibers, obtaining a maximum sensitivity of 0.1174 nm\/% v\/v. In this case, the transmitted optical signal analyzed at the end of the optical fiber allowed the identification of spectral shifts toward longer wavelengths with increasing EtOH concentration. In the study, the behavior of the spectral parameters of the interferometric curved optical fibers was analyzed as a function of the geometric parameters, highlighting their low cost, easy tuning control of minimum intensity peaks and good sensitivity.<\/jats:p>","DOI":"10.3390\/s26123740","type":"journal-article","created":{"date-parts":[[2026,6,12]],"date-time":"2026-06-12T06:53:10Z","timestamp":1781247190000},"page":"3740","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Low-Cost Ethanol Concentration Sensor Based on a Balloon-like Curved Optical Fiber in a Mach\u2013Zehnder Interferometric Configuration"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4510-7779","authenticated-orcid":false,"given":"Luis F.","family":"Espejo-Bayona","sequence":"first","affiliation":[{"name":"Laboratorio de \u00d3ptica e Inform\u00e1tica, Departamento de F\u00edsica, Qu\u00edmica y Afines, Facultad de Ciencias B\u00e1sicas, Universidad Popular del Cesar, Valledupar 200001, Cesar, Colombia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1382-5784","authenticated-orcid":false,"given":"Sindi D.","family":"Horta-Pi\u00f1eres","sequence":"additional","affiliation":[{"name":"Laboratorio de \u00d3ptica e Inform\u00e1tica, Departamento de F\u00edsica, Qu\u00edmica y Afines, Facultad de Ciencias B\u00e1sicas, Universidad Popular del Cesar, Valledupar 200001, Cesar, Colombia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3485-3146","authenticated-orcid":false,"given":"Duber A.","family":"Avila","sequence":"additional","affiliation":[{"name":"Laboratorio de \u00d3ptica e Inform\u00e1tica, Departamento de F\u00edsica, Qu\u00edmica y Afines, Facultad de Ciencias B\u00e1sicas, Universidad Popular del Cesar, Valledupar 200001, Cesar, Colombia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"111782","DOI":"10.1016\/j.sna.2019.111782","article-title":"A review of optical interferometry techniques for VOC detection","volume":"302","author":"Khan","year":"2020","journal-title":"Sens. Actuators A Phys."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"11109","DOI":"10.1364\/OE.20.011109","article-title":"All-fiber Mach Zehnder interferometers for sensing applications","volume":"20","author":"Li","year":"2012","journal-title":"Opt. Express"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"110316","DOI":"10.1016\/j.apacoust.2024.110316","article-title":"Applying Michelson-interferometer based optical fiber sensors for active control of road noise in a car","volume":"228","author":"Wang","year":"2025","journal-title":"Appl. Acoust."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"13071","DOI":"10.1021\/acsami.3c18702","article-title":"Miniature optical fiber Fabry-Perot interferometer based on a single-crystal metal-organic framework for the detection and quantification of benzene and ethanol at low concentrations in nitrogen gas","volume":"16","author":"Mumtaz","year":"2024","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"10643","DOI":"10.1364\/OE.23.010643","article-title":"Morphology dependent polymeric capillary optical resonator hydrostatic pressure sensor","volume":"23","author":"Gouveia","year":"2015","journal-title":"Opt. Express"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Taha, B.A., Ali, N., Sapiee, N.M., Fadhel, M.M., Yeh, R.M., Bachok, N.N., Mashhadany, Y.A., and Arsad, N. (2021). Comprehensive Review Tapered Optical Fiber Configurations for Sensing Application: Trend and Challenges. Biosensors, 11.","DOI":"10.3390\/bios11080253"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Lopez-Torres, D., Elosua, C., and Arregui, F.J. (2020). Optical fiber sensors based on microstructured optical fibers to detect gases and volatile organic compounds a review. Sensors, 20.","DOI":"10.3390\/s20092555"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"012010","DOI":"10.1088\/1742-6596\/1219\/1\/012010","article-title":"Capillary resonator as optical sensor for the measurement of the hydrostatic pressure. A theoretical study of its sensitivity","volume":"1219","author":"Avila","year":"2019","journal-title":"J. Phys. Conf. Ser."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"449","DOI":"10.1002\/lpor.200810034","article-title":"Optical sensing with photonic crystal fibers","volume":"2","author":"Frazao","year":"2008","journal-title":"Laser Photonics Rev."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"8861","DOI":"10.3390\/s120708861","article-title":"Microfiber-based Bragg Gratings for Sensing Applications: A review","volume":"12","author":"Kou","year":"2012","journal-title":"Sensors"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1224","DOI":"10.1364\/OL.26.001224","article-title":"Fiber optic liquid level sensor using a long period grating","volume":"26","author":"Khaliq","year":"2001","journal-title":"Opt. Lett."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"490","DOI":"10.1007\/s00339-024-07631-3","article-title":"Performance parameters of a Ag coated evanescent field optical fiber sensor for temperature measurement via surface plasmon resonance","volume":"130","author":"Horta","year":"2024","journal-title":"Appl. Phys. A"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Miliou, A. (2021). In fiber interferometric based sensors: Overview and recent advances. Photonics, 8.","DOI":"10.3390\/photonics8070265"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1548","DOI":"10.1364\/AO.50.001548","article-title":"Refractive index sensing based on Mach Zehnder interferometer formed by three cascaded single mode fiber tapers","volume":"50","author":"Wu","year":"2011","journal-title":"Appl. Opt."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"100469","DOI":"10.1016\/j.sbsr.2021.100469","article-title":"Performance analysis of alcohols Sensing with optical sensor procedure using circular photonic cristal fiber (C-PCF) in the terahertz regime","volume":"35","author":"Hossain","year":"2022","journal-title":"Sens. Bio-Sens. Res."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Memon, S.F., Wang, R., Strunz, B., Chowdhry, B.S., Pembroke, J.T., and Lewis, E. (2022). A review of optical fiber ethanol sensors: Current state and future prospects. Sensors, 22.","DOI":"10.3390\/s22030950"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"171854","DOI":"10.1016\/j.ijleo.2024.171854","article-title":"Simultaneous measurement of refractive index and temperature using a balloon-type optical fiber sensor","volume":"309","author":"Freitas","year":"2024","journal-title":"Optik"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"2","DOI":"10.3390\/photonics13010002","article-title":"Balloon-shaped optical fiber humidity sensor base on PVA coating for respiratory monitoring","volume":"13","author":"Shi","year":"2026","journal-title":"Photonics"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1008","DOI":"10.1007\/s12596-022-00916-x","article-title":"Asymmetric Mach Zehnder interferometer based optical sensor with characteristics of both wavelength and temperature independence","volume":"52","author":"Luo","year":"2023","journal-title":"J. Opt."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"00028","DOI":"10.1051\/epjconf\/202430500028","article-title":"Desing and fabrication of asymmetric Mach-Zehnder interferometers based on EpoClad and EpoCore strip waveguides","volume":"305","author":"Magalhaes","year":"2024","journal-title":"EPJ Web Conf."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1016\/j.optlastec.2018.01.008","article-title":"Highly Sensitive force sensor based on balloon-like interferometer","volume":"103","author":"Wu","year":"2018","journal-title":"Opt. Laser Technol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"114097","DOI":"10.1016\/j.measurement.2023.114097","article-title":"Measurement of refractive index and temperature using a balloon-like interferometer with an inner embedded waist-enlarged structure","volume":"226","author":"Liu","year":"2024","journal-title":"Measurement"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"09038","DOI":"10.1051\/epjconf\/202328709038","article-title":"Refractive index measurements of ethanol water binary liquid solutions using a graded index fiber tip sensor","volume":"287","author":"Soares","year":"2023","journal-title":"EPJ Web Conf."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1140\/epje\/i2009-10496-4","article-title":"Concentration and temperature dependence of the refractive index of ethanol water mixtures: Influence of intermolecular interactions","volume":"30","author":"Rioboo","year":"2009","journal-title":"Eur. Phys. J. E. Soft. Matter"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Ding, X., Lin, Q., Liu, S., Zhang, L., Chen, N., Zhang, Y., and Wang, Y. (2024). Highly Sensitive Balloon-like fiber interferometer base on ethanol coated for temperature measurement. Sensors, 24.","DOI":"10.3390\/s24113684"},{"key":"ref_26","unstructured":"Snyder, A.W., and Love, J.D. (1983). Optical Waveguide Theory, Springer."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"125","DOI":"10.1016\/j.molliq.2006.07.001","article-title":"Correlation of density and refraction index for liquid binary mixtures containing polyglycols. Use of the group contributions in the Lorentz\u2013Lorenz, Gladstone\u2013Dale and Vogel equations to evaluate the density of mixtures","volume":"133","author":"Francesconi","year":"2007","journal-title":"J. Mol. Liq."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"47","DOI":"10.1016\/j.combustflame.2019.12.023","article-title":"Implications of real-gas behavior on refractive index calculations for optical diagnostics of fuel\u2013air mixing at high pressures","volume":"214","author":"Wanstall","year":"2020","journal-title":"Combust. Flame"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"102277","DOI":"10.1016\/j.yofte.2020.102277","article-title":"Simultaneous measurement of displacement and temperature based on two cascaded ballon-like bent fibre structures","volume":"58","author":"Tian","year":"2020","journal-title":"Opt. Fiber Technol."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/12\/3740\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,14]],"date-time":"2026-06-14T04:12:00Z","timestamp":1781410320000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/12\/3740"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,6,12]]},"references-count":29,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2026,6]]}},"alternative-id":["s26123740"],"URL":"https:\/\/doi.org\/10.3390\/s26123740","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,6,12]]}}}