{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,9]],"date-time":"2026-05-09T18:22:02Z","timestamp":1778350922666,"version":"3.51.4"},"reference-count":28,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2017,10,16]],"date-time":"2017-10-16T00:00:00Z","timestamp":1508112000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61735010"],"award-info":[{"award-number":["61735010"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61675147"],"award-info":[{"award-number":["61675147"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61405144"],"award-info":[{"award-number":["61405144"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A relative humidity (RH) sensor based on single-mode\u2013no-core\u2013single-mode fiber (SNCS) structure is proposed and experimentally demonstrated. The agarose gel is coated on the no-core fiber (NCF) as the cladding, and multimode interference (MMI) occurs in the SNCS structure. The transmission spectrum of the sensor is modulated at different ambient relative humidities due to the tunable refractive index property of the agarose gel film. The relative humidity can be measured by the wavelength shift and intensity variation of the dip in the transmission spectra. The humidity response of the sensors, coated with different concentrations and coating numbers of the agarose solution, were experimentally investigated. The wavelength and intensity sensitivity is obtained as \u2212149 pm\/%RH and \u22120.075 dB\/%RH in the range of 30% RH to 75% RH, respectively. The rise and fall time is tested to be 4.8 s and 7.1 s, respectively. The proposed sensor has a great potential in real-time RH monitoring.<\/jats:p>","DOI":"10.3390\/s17102353","type":"journal-article","created":{"date-parts":[[2017,10,16]],"date-time":"2017-10-16T11:11:09Z","timestamp":1508152269000},"page":"2353","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":38,"title":["Relative Humidity Sensor Based on No-Core Fiber Coated by Agarose-Gel Film"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6021-0996","authenticated-orcid":false,"given":"Wei","family":"Xu","sequence":"first","affiliation":[{"name":"Institute of Laser and Optoelectronics, College of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China"},{"name":"Key Laboratory of Optoelectronic Information Science and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China"},{"name":"Tianjin Key Laboratory of Optoelectronic Detection Technology and Systems, Tianjin Polytechnic University, Tianjin 300387, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7563-9982","authenticated-orcid":false,"given":"Jia","family":"Shi","sequence":"additional","affiliation":[{"name":"Institute of Laser and Optoelectronics, College of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China"},{"name":"Key Laboratory of Optoelectronic Information Science and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xianchao","family":"Yang","sequence":"additional","affiliation":[{"name":"Institute of Laser and Optoelectronics, College of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China"},{"name":"Key Laboratory of Optoelectronic Information Science and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Degang","family":"Xu","sequence":"additional","affiliation":[{"name":"Institute of Laser and Optoelectronics, College of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China"},{"name":"Key Laboratory of Optoelectronic Information Science and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Feng","family":"Rong","sequence":"additional","affiliation":[{"name":"Tianjin Key Laboratory of Optoelectronic Detection Technology and Systems, Tianjin Polytechnic University, Tianjin 300387, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Junfa","family":"Zhao","sequence":"additional","affiliation":[{"name":"Tianjin Key Laboratory of Optoelectronic Detection Technology and Systems, Tianjin Polytechnic University, Tianjin 300387, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jianquan","family":"Yao","sequence":"additional","affiliation":[{"name":"Institute of Laser and Optoelectronics, College of Precision Instrument and Optoelectronic Engineering, Tianjin University, Tianjin 300072, China"},{"name":"Key Laboratory of Optoelectronic Information Science and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,10,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"4087","DOI":"10.1109\/JLT.2017.2730484","article-title":"A Humidity Sensor Based on a Singlemode-Side Polished Multimode\u2013Singlemode Optical Fibre Structure Coated with Gelatin","volume":"35","author":"Wang","year":"2017","journal-title":"J. Lightwave Technol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1109\/JSEN.2003.822214","article-title":"High-sensitivity sensor of low relative humidity based on overlay on side-polished fibers","volume":"4","author":"Guerrero","year":"2004","journal-title":"IEEE Sens. J."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"3884","DOI":"10.1364\/AO.52.003884","article-title":"Experimental demonstration of a high-sensitivity humidity sensor based on an Agarose-coated transmission-type photonic crystal fiber interferometer","volume":"52","author":"Mathew","year":"2013","journal-title":"Appl. Opt."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"21216","DOI":"10.1364\/OE.24.021216","article-title":"Agarose coated spherical micro resonator for humidity measurements","volume":"24","author":"Mallik","year":"2016","journal-title":"Opt. Exp."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"3424","DOI":"10.1109\/JSEN.2015.2389519","article-title":"Relative Humidity Sensor Based on S-Taper Fiber Coated with SiO2 Nanoparticles","volume":"15","author":"Liu","year":"2015","journal-title":"IEEE Sens. J."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1945","DOI":"10.1109\/JSEN.2014.2368979","article-title":"A Study of Relative Humidity Fiber-Optic Sensors","volume":"15","author":"Batumalay","year":"2015","journal-title":"IEEE Sens. J."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"5450","DOI":"10.1109\/JSEN.2015.2444100","article-title":"Novel Fiber-Optic Relative Humidity Sensor with Thermal Compensation","volume":"15","author":"Korenko","year":"2015","journal-title":"IEEE Sens. J."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"441","DOI":"10.1109\/LPT.2009.2013185","article-title":"Relative Humidity Sensor Based on Tilted Fiber Bragg Grating with Polyvinyl Alcohol Coating","volume":"21","author":"Miao","year":"2009","journal-title":"IEEE Photonics Tehnol. Lett."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1206","DOI":"10.1364\/OE.24.001206","article-title":"Temperature insensitive hysteresis free highly sensitive polymer optical fiber Bragg grating humidity sensor","volume":"24","author":"Woyessa","year":"2016","journal-title":"Opt. Exp."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"880","DOI":"10.1109\/LPT.2007.897551","article-title":"Long-Period Grating Relative Humidity Sensor with Hydrogel Coating","volume":"19","author":"Liu","year":"2007","journal-title":"IEEE Photonics Tehnol. Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.sna.2012.10.041","article-title":"Novel optical fiber humidity sensor based on a no-core fiber structure","volume":"190","author":"Xia","year":"2013","journal-title":"Sens. Actuators A Phys."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"414","DOI":"10.1016\/j.snb.2010.02.029","article-title":"Tunable humidity sensor based on ITO-coated optical fiber","volume":"146","author":"Hernaez","year":"2010","journal-title":"Sens. Actuators B Chem."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"618","DOI":"10.1016\/j.snb.2015.08.108","article-title":"Humidity sensor based on power leakage at resonance wavelengths of a hollow core fiber coated with reduced graphene oxide","volume":"222","author":"Gao","year":"2016","journal-title":"Sens. Actuators B Chem."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1752","DOI":"10.1364\/OL.36.001752","article-title":"Humidity sensor based on a single-mode hetero-core fiber structure","volume":"36","author":"Wu","year":"2011","journal-title":"Opt. Lett."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"385","DOI":"10.1016\/j.snb.2010.03.049","article-title":"A humidity sensor based on a hetero-core optical fiber","volume":"147","author":"Akita","year":"2010","journal-title":"Sens. Actuators B Chem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2127","DOI":"10.1109\/LPT.2015.2454271","article-title":"Optical Fiber Fabry-Perot Humidity Sensor Based on Porous Al2O3 Film","volume":"27","author":"Huang","year":"2015","journal-title":"IEEE Photonics Tehnol. Lett."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2027","DOI":"10.1109\/LPT.2016.2581990","article-title":"Agarose Filled Fabry-Perot Cavity for Temperature Self-Calibration Humidity Sensing","volume":"28","author":"Wang","year":"2016","journal-title":"IEEE Photonics Tehnol. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"696","DOI":"10.1016\/j.snb.2016.03.102","article-title":"High-birefringence microfiber Sagnac interferometer based humidity sensor","volume":"231","author":"Sun","year":"2016","journal-title":"Sens. Actuators B Chem."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3460","DOI":"10.1109\/JLT.2013.2283943","article-title":"Optimization of Sensors Based on Multimode Interference in Single-Mode-Multimode-Single-Mode Structure","volume":"31","author":"Villar","year":"2013","journal-title":"J. Lightwave Technol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"17817","DOI":"10.3390\/s140917817","article-title":"Gasohol Quality Control for Real Time Applications by Means of a Multimode Interference Fiber Sensor","volume":"14","author":"Rodriguez","year":"2014","journal-title":"Sensors"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"314","DOI":"10.1109\/JSTQE.2016.2633819","article-title":"Fiber-Optic Immunosensor Based on an Etched SMS Structure","volume":"23","author":"Socorro","year":"2017","journal-title":"IEEE J. Sel. Top. Quantum Electron."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1998","DOI":"10.1364\/OL.37.001998","article-title":"Fiber ring laser interrogated zeolite-coated singlemode-multimode-singlemode structure for trace chemical detection","volume":"37","author":"Lan","year":"2012","journal-title":"Opt. Lett."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1463","DOI":"10.1109\/JLT.2012.2186433","article-title":"Sensitivity enhancement of RI sensor based on SMS fiber structure with high refractive index overlay","volume":"30","author":"Xue","year":"2012","journal-title":"J. Lightwave Technol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"363","DOI":"10.1016\/j.snb.2013.08.090","article-title":"Sensitivity enhancement in a multimode interference-based SMS fibre structure coated with a thin-film: Theoretical and experimental study","volume":"190","author":"Socorro","year":"2014","journal-title":"Sens. Actuators B Chem."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"3913","DOI":"10.1364\/AO.53.003913","article-title":"Refractometric sensors based on multimode interference in a thin-film coated single-mode-multimode-single-mode structure with reflection configuration","volume":"53","author":"Villar","year":"2014","journal-title":"Appl. Opt."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"127","DOI":"10.1016\/S0925-4005(00)00524-4","article-title":"Optical fiber humidity sensor based on a tapered fiber coated with agarose gel","volume":"69","author":"Bariain","year":"2000","journal-title":"Sens. Actuators B Chem."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"6313","DOI":"10.1364\/OE.21.006313","article-title":"Effect of coating thickness on the sensitivity of a humidity sensor based on an Agarose coated photonic crystal fiber interferometer","volume":"21","author":"Mathew","year":"2013","journal-title":"Opt. Exp."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"313","DOI":"10.1016\/j.snb.2014.01.061","article-title":"Agarose gel filled temperature-insensitive photonic crystal fibers humidity sensor based on the tunable coupling ratio","volume":"195","author":"Gao","year":"2014","journal-title":"Sens. Actuators B Chem."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/10\/2353\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:47:25Z","timestamp":1760208445000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/10\/2353"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,10,16]]},"references-count":28,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2017,10]]}},"alternative-id":["s17102353"],"URL":"https:\/\/doi.org\/10.3390\/s17102353","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2017,10,16]]}}}