{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:03:32Z","timestamp":1760238212904,"version":"build-2065373602"},"reference-count":30,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2020,7,13]],"date-time":"2020-07-13T00:00:00Z","timestamp":1594598400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["SFRH\/BD\/110035\/2015"],"award-info":[{"award-number":["SFRH\/BD\/110035\/2015"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100010661","name":"Horizon 2020 Framework Programme","doi-asserted-by":"publisher","award":["688735"],"award-info":[{"award-number":["688735"]}],"id":[{"id":"10.13039\/100010661","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Long period fiber gratings (LPFGs) were fabricated in a standard single mode fiber (SMF-28e) through femtosecond (fs) laser direct writing. LPFGs with longer and shorter periods were fabricated, which allows coupling from the fundamental core mode to lower and higher order asymmetric cladding modes (LP1,6 and LP1,12, respectively). For the grating periods of 182.7 and 192.5 \u00b5m, it was verified that the LP1,12 mode exhibits a TAP at approximately 1380 and 1448 nm in air and water, respectively. Characterization of the LPFGs subjected to high-temperature thermal treatment was accomplished. Fine-tuning of the resonance band\u2019s position and thermal stability up to 600 \u00b0C was shown. The temperature sensitivity was characterized for the gratings with different periods and for different temperature ranges. A maximum sensitivity of \u2212180.73, and 179.29 pm\/\u00b0C was obtained for the two resonances of the 182.7 \u00b5m TAP LPFG, in the range between 250 and 600 \u00b0C.<\/jats:p>","DOI":"10.3390\/s20143898","type":"journal-article","created":{"date-parts":[[2020,7,14]],"date-time":"2020-07-14T09:30:49Z","timestamp":1594719049000},"page":"3898","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Temperature Stability and Spectral Tuning of Long Period Fiber Gratings Fabricated by Femtosecond Laser Direct Writing"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0674-9963","authenticated-orcid":false,"given":"Duarte","family":"Viveiros","sequence":"first","affiliation":[{"name":"Center for Applied Photonics, INESC TEC, 4200-465 Porto, Portugal"},{"name":"Department of Physics and Astronomy, Faculty of Science, University of Porto, 4169-007 Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3810-5943","authenticated-orcid":false,"given":"Jos\u00e9 M. M. M.","family":"de Almeida","sequence":"additional","affiliation":[{"name":"Center for Applied Photonics, INESC TEC, 4200-465 Porto, Portugal"},{"name":"Department of Physics, University of Tr\u00e1s-os-Montes e Alto Douro, 5001-801 Vila Real, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6205-9479","authenticated-orcid":false,"given":"Lu\u00eds","family":"Coelho","sequence":"additional","affiliation":[{"name":"Center for Applied Photonics, INESC TEC, 4200-465 Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Helena","family":"Vasconcelos","sequence":"additional","affiliation":[{"name":"Center for Applied Photonics, INESC TEC, 4200-465 Porto, Portugal"},{"name":"Department of Physics, University of Tr\u00e1s-os-Montes e Alto Douro, 5001-801 Vila Real, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jo\u00e3o M.","family":"Maia","sequence":"additional","affiliation":[{"name":"Center for Applied Photonics, INESC TEC, 4200-465 Porto, Portugal"},{"name":"Department of Physics and Astronomy, Faculty of Science, University of Porto, 4169-007 Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"V\u00edtor A.","family":"Amorim","sequence":"additional","affiliation":[{"name":"Center for Applied Photonics, INESC TEC, 4200-465 Porto, Portugal"},{"name":"Department of Physics and Astronomy, Faculty of Science, University of Porto, 4169-007 Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1484-2068","authenticated-orcid":false,"given":"Pedro A. S.","family":"Jorge","sequence":"additional","affiliation":[{"name":"Center for Applied Photonics, INESC TEC, 4200-465 Porto, Portugal"},{"name":"Department of Physics and Astronomy, Faculty of Science, University of Porto, 4169-007 Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Paulo V. S.","family":"Marques","sequence":"additional","affiliation":[{"name":"Center for Applied Photonics, INESC TEC, 4200-465 Porto, Portugal"},{"name":"Department of Physics and Astronomy, Faculty of Science, University of Porto, 4169-007 Porto, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,7,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"R49","DOI":"10.1088\/0957-0233\/14\/5\/201","article-title":"Optical fibre long\u2013period grating sensors: Characteristics and application","volume":"14","author":"James","year":"2003","journal-title":"Meas. Sci. 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