{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T10:41:16Z","timestamp":1783593676478,"version":"3.55.0"},"reference-count":29,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2019,4,10]],"date-time":"2019-04-10T00:00:00Z","timestamp":1554854400000},"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":["61735013,61705169"],"award-info":[{"award-number":["61735013,61705169"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003819","name":"Natural Science Foundation of Hubei Province","doi-asserted-by":"publisher","award":["2018CFA056"],"award-info":[{"award-number":["2018CFA056"]}],"id":[{"id":"10.13039\/501100003819","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Crack generation starts at the crack tip, which bears the highest stress concentration. Under further stress, the crack propagates and leads to severe structural damage. To avoid such damage, the identification of the crack tips, and monitoring of the surrounding stress and strain fields, are very important. In this work, the location of, and strain distribution monitoring around, the crack tip are achieved using a dense ultra-short (DUS) fiber Bragg grating (FBG) array together with an improved optical frequency domain reflectometry (OFDR) interrogator. The adjacent grating interference correlation algorithm helps overcome the limitation on the demodulation precision, which is imposed by the inherently broad reflection spectra of individual ultra-short gratings. High spatial resolution measurement of the strain profile around the crack tip is performed at different levels of induced strain. Furthermore, the vertical-crossed layout is adopted to avoid the omission of cracks, which usually occurs in the case of the one direction layout. We achieve 1 mm spatial resolution and 7.5 m detection distance. Location of a single crack, multiple cracks, and an oblique crack was realized experimentally by locating the crack tips. The experimental results are consistent with the theoretical analysis, verifying the feasibility of the DUS-FBG system for high-density distributed crack tip sensing.<\/jats:p>","DOI":"10.3390\/s19071702","type":"journal-article","created":{"date-parts":[[2019,4,10]],"date-time":"2019-04-10T03:47:36Z","timestamp":1554868056000},"page":"1702","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["High-Density Distributed Crack Tip Sensing System Using Dense Ultra-Short FBG Sensors"],"prefix":"10.3390","volume":"19","author":[{"given":"Xin","family":"Gui","sequence":"first","affiliation":[{"name":"School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China"},{"name":"National Engineering Laboratory for Fiber Optic Sensing Technology, Wuhan University of Technology, Wuhan 430070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4600-2795","authenticated-orcid":false,"given":"Zhengying","family":"Li","sequence":"additional","affiliation":[{"name":"School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xuelei","family":"Fu","sequence":"additional","affiliation":[{"name":"School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Changjia","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yiming","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hongli","family":"Li","sequence":"additional","affiliation":[{"name":"School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Honghai","family":"Wang","sequence":"additional","affiliation":[{"name":"National Engineering Laboratory for Fiber Optic Sensing Technology, Wuhan University of Technology, Wuhan 430070, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2019,4,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"903","DOI":"10.1016\/j.compositesa.2004.12.005","article-title":"Delamination monitoring of laminated composites subjected to low-velocity impact using small-diameter FBG sensors","volume":"36","author":"Takeda","year":"2005","journal-title":"Compos. Part A Appl. Sci. Manuf."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"209","DOI":"10.1016\/j.yofte.2006.12.003","article-title":"Investigation of fatigue crack in stainless steel using a mobile fiber Bragg grating ultrasonic sensor","volume":"13","author":"Tsuda","year":"2007","journal-title":"Opt. Fiber Technol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"813","DOI":"10.1016\/j.compstruct.2011.02.020","article-title":"Damage monitoring of CFRP stiffened panels under compressive load using FBG sensors","volume":"94","author":"Takeda","year":"2012","journal-title":"Compos. Struct."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"151","DOI":"10.1016\/j.compstruct.2015.11.037","article-title":"FBG-based real-time evaluation of transverse cracking in cross-ply laminates","volume":"138","author":"Hu","year":"2016","journal-title":"Compos. Struct."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Zhang, W., Zhang, M., Wang, X., Zhao, Y., Jin, B., and Dai, W. (2019). The Analysis of FBG Central Wavelength Variation with Crack Propagation Based on a Self-Adaptive Multi-Peak Detection Algorithm. Sensors, 19.","DOI":"10.3390\/s19051056"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Ding, Z., Wang, C., Liu, K., Jiang, J., Pan, G., Pu, Z., and Liu, T. (2018). Distributed optical fiber sensors based on optical frequency domain reflectometry: A review. Sensors, 18.","DOI":"10.3390\/s18041072"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"763","DOI":"10.1088\/0964-1726\/16\/3\/025","article-title":"Debonding monitoring of composite repair patches using embedded small-diameter FBG sensors","volume":"16","author":"Takeda","year":"2007","journal-title":"Smart Mater. Struct."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"55025","DOI":"10.1088\/0964-1726\/21\/5\/055025","article-title":"Memorizing and detecting an arrested crack in a foam-core sandwich structure using embedded plastic materials and fiber-optic sensors","volume":"21","author":"Minakuchi","year":"2012","journal-title":"Smart Mater. Struct."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2857693","DOI":"10.1155\/2017\/2857693","article-title":"Mechanism of Subordinate Peak Skewing of FBG Sensor during Cracks Propagation Monitoring on Aluminum Alloy Structure","volume":"2017","author":"Jin","year":"2017","journal-title":"J. Sens."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Jin, B., Zhang, W., Zhang, M., Ren, F., Dai, W., and Wang, Y. (2017). Investigation on characteristic variation of the FBG spectrum with crack propagation in aluminum plate structures. Materials, 10.","DOI":"10.3390\/ma10060588"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"178","DOI":"10.1016\/j.measurement.2018.03.023","article-title":"Evaluation of delamination crack tip in woven fibre glass reinforced polymer composite using FBG sensor spectra and thermo-elastic response","volume":"122","author":"Kakei","year":"2018","journal-title":"Measurement"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1423","DOI":"10.1088\/0964-1726\/16\/4\/057","article-title":"An experimental numerical study of the response of a long fibre Bragg grating sensor near a crack tip","volume":"16","author":"Colpo","year":"2007","journal-title":"Smart Mater. Struct."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"105011","DOI":"10.1088\/0964-1726\/23\/10\/105011","article-title":"Dynamic strain distribution measurement and crack detection of an adhesive-bonded single-lap joint under cyclic loading using embedded FBG","volume":"23","author":"Ning","year":"2014","journal-title":"Smart Mater. Struct."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2879","DOI":"10.1016\/j.compstruct.2012.03.032","article-title":"Crack tip identification with long FBG sensors in mixed-mode delamination","volume":"94","author":"Sans","year":"2012","journal-title":"Comopos. Struct."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1016\/j.msea.2009.07.013","article-title":"Mechanical behavior and crack tip plasticity of a strain aging sensitive steel","volume":"526","author":"Belotteau","year":"2009","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2","DOI":"10.1002\/mop.10653","article-title":"Intrinsic crosstalk analysis of a serial TDM FGB sensor array by using a tunable laser","volume":"36","author":"Chan","year":"2003","journal-title":"Microw. Opt. Technol. Lett."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"666","DOI":"10.1364\/OPEX.13.000666","article-title":"High resolution optical frequency domain reflectometry for characterization of components and assemblies","volume":"13","author":"Soller","year":"2005","journal-title":"Opt. Express"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"31484","DOI":"10.1364\/OE.23.031484","article-title":"Large-capacity multiplexing of near-identical weak fiber Bragg gratings using frequency-shifted interferometry","volume":"23","author":"Ou","year":"2015","journal-title":"Opt. Express"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2430","DOI":"10.1364\/OL.43.002430","article-title":"High-speed demodulation of weak fiber Bragg gratings based on microwave photonics and chromatic dispersion","volume":"43","author":"Zhou","year":"2018","journal-title":"Opt. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1249","DOI":"10.1109\/LPT.2017.2712182","article-title":"A High-Speed Distributed Ultra-Weak FBG Sensing System with High Resolution","volume":"29","author":"Han","year":"2017","journal-title":"IEEE Photonics Technol. Lett."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"2751","DOI":"10.1109\/JLT.2012.2205897","article-title":"A large serial time-division multiplexed fiber bragg grating sensor network","volume":"30","author":"Wang","year":"2012","journal-title":"J. Lightwave Technol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"22799","DOI":"10.1364\/OE.21.022799","article-title":"A time- and wavelength-division multiplexing sensor network with ultra-weak fiber Bragg gratings","volume":"21","author":"Luo","year":"2013","journal-title":"Opt. Express"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"5259","DOI":"10.1364\/OL.43.005259","article-title":"Large-scale multiplexing of a FBG array with randomly varied characteristic parameters for distributed sensing","volume":"43","author":"Xin","year":"2018","journal-title":"Opt. Lett."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"17437","DOI":"10.1364\/OE.26.017437","article-title":"Simultaneous distributed static and dynamic sensing based on ultra-short fiber Bragg gratings","volume":"26","author":"Li","year":"2018","journal-title":"Opt Express"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"2466","DOI":"10.1364\/OE.24.002466","article-title":"Ultra-short FBG based distributed sensing using shifted optical Gaussian filters and microwave-network analysis","volume":"24","author":"Cheng","year":"2016","journal-title":"Opt. Express"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"5254","DOI":"10.1364\/OL.41.005254","article-title":"Interrogation of weak bragg grating sensors based on dual-wavelength differential detection","volume":"41","author":"Rui","year":"2016","journal-title":"Opt. Lett."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1109\/JPHOT.2014.2320742","article-title":"Long-Range High Spatial Resolution Distributed Temperature and Strain Sensing Based on Optical Frequency-Domain Reflectometry","volume":"6","author":"Song","year":"2014","journal-title":"IEEE Photonics Technol. Lett."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"28112","DOI":"10.1364\/OE.25.028112","article-title":"Distributed sensing technology of high-spatial resolution based on dense ultra-short FBG array with large multiplexing capacity","volume":"25","author":"Gui","year":"2017","journal-title":"Opt. Express"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"035201","DOI":"10.1088\/1361-6501\/aaa2ef","article-title":"Research on a high-precision calibration method for tunable lasers","volume":"29","author":"Xiang","year":"2018","journal-title":"Meas. Sci. Technol."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/7\/1702\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T12:44:09Z","timestamp":1760186649000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/7\/1702"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,4,10]]},"references-count":29,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2019,4]]}},"alternative-id":["s19071702"],"URL":"https:\/\/doi.org\/10.3390\/s19071702","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,4,10]]}}}