An investigation into the wavelength stability of polymer optical fibre Bragg gratings

Wei Zhang, Ada Abang, David J. Webb, Gang-Ding Peng

Research output: Chapter in Book/Published conference outputConference publication


The inscription of Bragg gratings has been demonstrated in PMMA-based polymer optical fibre. The water affinity of PMMA can introduce significant wavelength change in a polymer optical fibre Bragg grating (POFBG). In polymer optical fibre losses are much higher than with silica fibre. Very strong absorption bands related to higher harmonics of vibrations of the C-H bond dominate throughout the visible and near infrared. Molecular vibration in substances generates heat, which is referred to as the thermal effect of molecular vibration. This means that a large part of the absorption of optical energy in those spectral bands will convert into thermal energy, which eventually drives water content out of the polymer fibre and reduces the wavelength of POFBG. In this work we have investigated the wavelength stability of POFBGs in different circumstances. The experiment has shown that the characteristic wavelength of a POFBG starts decreasing after a light source is applied to it. This decrease continues until equilibrium inside the fibre is established, depending on the initial water content inside the fibre, the surrounding humidity, the optical power applied, and the fibre size. Our investigation has shown that POFBGs operating at around 850 nm show much smaller wavelength reduction than those operating at around 1550 nm in the same fibre; POFBGs with different diameters show different changes; POFBGs powered by a low level light source, or operating in a very dry environment are least affected by this thermal effect.
Original languageEnglish
Title of host publicationMicro-structured and specialty optical fibres
EditorsKyriacos Kalli, Alexis Mendez
Number of pages8
Publication statusPublished - 2012
EventMicrostructured and specialty optical fibres - Brussels, Belgium
Duration: 17 Apr 201219 Apr 2012

Publication series

NameSPIE proceedings
ISSN (Print)0277-786X


ConferenceMicrostructured and specialty optical fibres

Bibliographical note

Zhang, Wei; Abang, Ada; Webb, David J.; Peng, Gang-Ding, "An investigation into the wavelength stability of polymer optical fibre Bragg gratings" In: Micro-structured and specialty optical fibres. ed. Kyriacos Kalli; Alexis Mendez. Vol. 8426 SPIE, 2012.

Copyright 2012 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.


  • polymer optical fibre
  • PMMA
  • fibre Bragg grating
  • humidity
  • optical absorption
  • molecular vibration
  • thermal effect
  • polymer swelling


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