Liquid level sensor utilising a long period fiber grating

Steven Grice*, Wei Zhang, Kate Sugden, Ian Bennion

*Corresponding author for this work

Research output: Chapter in Book/Published conference outputConference publication


We propose here a liquid level sensor using a long period fiber grating (LPFG) in which direct liquid level measurement is carried out by utilising an LPFG, 100mm in length and a periodicity of 1mm. The LPFG was exposed to liquids with varying levels and the wavelength shift of a selected loss band of the transmission spectra was monitored using a broadband light source and an optical spectrum analyzer. The mechanism of this LPFG sensor is based on the fact that the effective Refractive Index (RI) of a cladding mode is directly dependant on the RI of the surrounding medium, be it air, or in this case water and petrol. As the surrounding RI changes, so does the phase matching condition of the LPFG. The result for the level change of the liquid with a specific RI is both a shift in wavelength and a change in the attenuation level of the selected loss band. For the selected loss band, continuous wavelength shifts of 9.5 nm and 25 nm for 100 mm of water and petrol level change have been observed respectively, with sub-millimetre accuracy.

Original languageEnglish
Title of host publicationOptical Components and Materials VI
EditorsShibin Jiang, Michel J.F. Digonnet, John W. Glesener, J. Christopher Dries
Place of PublicationBellingham, WA (US)
Number of pages8
ISBN (Print)978-0-8194-7458-2
Publication statusPublished - 6 Feb 2009
EventOptical Components and Materials VI - San Jose, CA, United States
Duration: 26 Jan 200928 Jan 2009

Publication series

NameSPIE Proceedings
ISSN (Print)0277-786X
ISSN (Electronic)2410-9045


ConferenceOptical Components and Materials VI
Country/TerritoryUnited States
CitySan Jose, CA

Bibliographical note

S. Grice ; W. Zhang ; K. Sugden and I. Bennion; "Liquid level sensor utilising a long period fiber grating", Proc. SPIE 7212, Optical Components and Materials VI, 72120C (February 06, 2009).

Copyright 2009 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print 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.



  • Broad Band Source
  • liquid level sensing
  • long period Fiber grating
  • optical spectrum analyzer
  • refractive index
  • LPFG
  • BBS


Dive into the research topics of 'Liquid level sensor utilising a long period fiber grating'. Together they form a unique fingerprint.

Cite this