Fast bragg grating inscription in PMMA polymer optical fibres: impact of thermal pre-treatment of preforms

Carlos A.F. Marques*, Andreas Pospori, Gökhan Demirci, Onur Çetinkaya, Barbara Gawdzik, Paulo Antunes, Ole Bang, Pawel Mergo, Paulo André, David J. Webb

*Corresponding author for this work

Research output: Contribution to journalSpecial issuepeer-review

Abstract

In this work, fibre Bragg gratings (FBGs) were inscribed in two different undoped poly- (methyl methacrylate) (PMMA) polymer optical fibres (POFs) using different types of UV lasers and their inscription times, temperature and strain sensitivities are investigated. The POF Bragg gratings (POFBGs) were inscribed using two UV lasers: a continuous UV HeCd @325 nm laser and a pulsed UV KrF @248 nm laser. Two PMMA POFs are used in which the primary and secondary preforms (during the two-step drawing process) have a different thermal treatment. The PMMA POFs drawn in which the primary or secondary preform is not specifically pre-treated need longer inscription time than the fibres drawn where both preforms have been pre-annealed at 80 °C for 2 weeks. Using both UV lasers, for the latter fibre much less inscription time is needed compared to another homemade POF. The properties of a POF fabricated with both preforms thermally well annealed are different from those in which just one preform step process is thermally treated, with the first POFs being much less sensitive to thermal treatment. The influence of annealing on the strain and temperature sensitivities of the fibres prior to FBG inscription is also discussed, where it is observed that the fibre produced from a two-step drawing process with well-defined pre-annealing of both preforms did not produce any significant difference in sensitivity. The results indicate the impact of preform thermal pre-treatment before the PMMA POFs drawing, which can be an essential characteristic in the view of developing POF sensors technology.

Original languageEnglish
Article number891
Number of pages8
JournalSensors
Volume17
Issue number4
DOIs
Publication statusPublished - 18 Apr 2017

Bibliographical note

© 2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Keywords

  • annealing process
  • Bragg gratings
  • POF sensors
  • polymer optical fiber
  • preform treatment

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