Distributed opto-mechanical analysis of liquids outside standard fibers coated with polyimide

Hilel Hagai Diamandi, Yosef London, Gil Bashan, Avi Zadok

Research output: Contribution to journalArticlepeer-review

51 Scopus citations

Abstract

The analysis of surrounding media has been a long-standing challenge of optical fiber sensors. Measurements are difficult due to the confinement of light to the inner core of standard fibers. Over the last two years, new sensor concepts have enabled the analysis of liquids outside the cladding boundary, where light does not reach. Sensing is based on opto-mechanical, forward stimulated Brillouin scattering (F-SBS) interactions between guided light and sound waves. In most previous studies, however, the protective polymer coating of the fiber had to be removed first. In this work, we report the opto-mechanical analysis of liquids outside commercially available, standard single-mode fibers with polyimide coating. The polyimide layer provides mechanical protection but can also transmit acoustic waves from the fiber cladding toward outside media. The comprehensive analysis of opto-mechanical coupling in coated fibers that are immersed in liquid is provided. The model shows that F-SBS spectra in coated fibers are more complex than those of bare fibers and strongly depend on the exact coating diameter and the choice of acoustic mode. Nevertheless, sensing outside coated fibers is demonstrated experimentally. Integrated measurements over 100 m of fiber clearly distinguish between air, ethanol, and water outside polyimide coating. Measured spectra are in close quantitative agreement with the analytic predictions. Furthermore, distributed opto-mechanical time-domain reflectometry mapping of water and ethanol outside coated fiber is reported, with a spatial resolution of 100 m. The results represent a large step toward practical opto-mechanical fiber sensors.

Original languageEnglish
Article number016105
JournalAPL Photonics
Volume4
Issue number1
DOIs
StatePublished - 1 Jan 2019

Bibliographical note

Publisher Copyright:
© 2019 Author(s).

Funding

The authors acknowledge the financial support of the European Research Council (ERC), Grant No. H2020-ERC-2015-STG 679228 (L-SID) and of the Israeli Ministry of Science and Technology, Grant No. 61047. H. Hagai Diamandi is grateful to the Azrieli Foundation for the award of an Azrieli Fellowship.

FundersFunder number
Horizon 2020 Framework Programme679228
European Commission
Azrieli Foundation
Ministry of science and technology, Israel61047

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