{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,27]],"date-time":"2026-02-27T15:32:36Z","timestamp":1772206356786,"version":"3.50.1"},"reference-count":16,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2023,1,5]],"date-time":"2023-01-05T00:00:00Z","timestamp":1672876800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Funds through the Portuguese funding agency, FCT-Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","award":["UIDB\/50014\/2020"],"award-info":[{"award-number":["UIDB\/50014\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this paper, a different Fiber Loop Mirror (FLM) configuration with two circulators is presented. This configuration is demonstrated and characterized for sensing applications. This new design concept was used for strain and torsion discrimination. For strain measurement, the interference fringe displacement has a sensitivity of (0.576 \u00b1 0.009) pm\u2027\u03bc\u03b5\u22121. When the FFT (Fast Fourier Transformer) is calculated and the frequency shift and signal amplitude are monitored, the sensitivities are (\u22122.1 \u00b1 0.3) \u00d7 10\u22124 nm\u22121 \u03bc\u03b5\u22121 and (4.9 \u00b1 0.3) \u00d7 10\u22127 \u03bc\u03b5\u22121, respectively. For the characterization in torsion, an FFT peaks variation of (\u22122.177 \u00b1 0.002) \u00d7 10\u221212 nm\u22121\/\u00b0 and an amplitude variation of (1.02 \u00b1 0.06) \u00d7 10\u22123\/\u00b0 are achieved. This configuration allows the use of a wide range of fiber lengths and with different refractive indices for controlling the free spectral range (FSR) and achieving refractive index differences, i.e., birefringence, higher than 10\u22122, which is essential for the development of high sensitivity physical parameter sensors, such as operating on the Vernier effect. Furthermore, this FLM configuration allows the system to be balanced, which is not possible with traditional FLMs.<\/jats:p>","DOI":"10.3390\/s23020618","type":"journal-article","created":{"date-parts":[[2023,1,5]],"date-time":"2023-01-05T05:29:48Z","timestamp":1672896588000},"page":"618","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Fiber Loop Mirror Based on Optical Fiber Circulator for Sensing Applications"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0384-1924","authenticated-orcid":false,"given":"Paulo","family":"Robalinho","sequence":"first","affiliation":[{"name":"Institute for Systems and Computer Engineering, Technology and Science (INESC TEC), 4169-007 Porto, Portugal"},{"name":"Faculty of Engineering, Porto University, 4200-465 Porto, Portugal"}]},{"given":"Beatriz","family":"Soares","sequence":"additional","affiliation":[{"name":"Institute for Systems and Computer Engineering, Technology and Science (INESC TEC), 4169-007 Porto, Portugal"},{"name":"Faculty of Engineering, Porto University, 4200-465 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2988-1222","authenticated-orcid":false,"given":"Ant\u00f3nio","family":"Lobo Ribeiro","sequence":"additional","affiliation":[{"name":"Faculty of Health Sciences, University Fernando Pessoa, 4200-150 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7555-361X","authenticated-orcid":false,"given":"Susana","family":"Silva","sequence":"additional","affiliation":[{"name":"Institute for Systems and Computer Engineering, Technology and Science (INESC TEC), 4169-007 Porto, Portugal"},{"name":"Faculty of Engineering, Porto University, 4200-465 Porto, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7680-1056","authenticated-orcid":false,"given":"Orlando","family":"Fraz\u00e3o","sequence":"additional","affiliation":[{"name":"Institute for Systems and Computer Engineering, Technology and Science (INESC TEC), 4169-007 Porto, Portugal"},{"name":"Faculty of Engineering, Porto University, 4200-465 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2023,1,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1016\/j.optcom.2007.05.016","article-title":"Reflectivity characteristics of the fiber loop mirror with a polarization controller","volume":"277","author":"Feng","year":"2007","journal-title":"Opt. 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