{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T14:18:21Z","timestamp":1785421101375,"version":"3.56.0"},"reference-count":20,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2026,7,11]],"date-time":"2026-07-11T00:00:00Z","timestamp":1783728000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100018789","name":"Kajima Foundation","doi-asserted-by":"publisher","award":["2026-08"],"award-info":[{"award-number":["2026-08"]}],"id":[{"id":"10.13039\/501100018789","id-type":"DOI","asserted-by":"publisher"}]},{"award":["2026-08"],"award-info":[{"award-number":["2026-08"]}],"id":[{"id":"https:\/\/ror.org\/043ga8x09","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This report proposes a debris flow detection system based on an optical fiber network. Optical communication devices, including a distributed feedback laser, fiber amplifier, and amplified photodetector are used in the detection system. A tree topology fiber network formed by multiple optical couplers and delay fibers is employed to increase the number of sensor lines in the sensing port. Fiber patch cables or fiber mirrors are used as sensor heads instead of electric cables. The time-division multiplexing technique is used to simultaneously monitor all sensors in the time domain. It is demonstrated that this setup can be used to realize a passive and robust sensor network for debris flow detection by performing simulation experiments at the laboratory level. Results for a five-stage tree-topology are presented, and the extensibility of the proposed approach to a seven-stage network is outlined.<\/jats:p>","DOI":"10.3390\/s26144409","type":"journal-article","created":{"date-parts":[[2026,7,13]],"date-time":"2026-07-13T08:05:31Z","timestamp":1783929931000},"page":"4409","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Debris Flow Detection System Based on Tree-Topology Optical Fiber Network"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6082-1658","authenticated-orcid":false,"given":"Keiji","family":"Kuroda","sequence":"first","affiliation":[{"name":"Department of Physics, School of Science, Kitasato University, Sagamihara 252-0373, Kanagawa, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"905","DOI":"10.5194\/nhess-15-905-2015","article-title":"Monitoring and prediction in early warning systems for rapid mass movements","volume":"15","author":"Stahli","year":"2015","journal-title":"Nat. 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