Measuring sensitivity of optical frequency transfers to acoustic vibrations in photonic networks

0568225 - ÚPT 2023 PL eng A - Abstract
Čížek, Martin - Pravdová, Lenka - Hrabina, Jan - Rajmic, P. - Horváth, T. - Schimmel, J. - Dejdar, P. - Mokrý, O. - Číp, Ondřej - Münster, P.
Measuring sensitivity of optical frequency transfers to acoustic vibrations in photonic networks.
Book of Abstracts. 22nd Polish-Slovak-Czech Optical Conference on Wave and Quantum Aspects of Contemporary Optics, September 5-9, 2022, Wojanów, Poland. Wrocław: Wroclaw University of Science and Technology, 2022 - (Sztylińska, K.). s. 151
[Polish-Slovak-Czech Optical Conference on Wave and Quantum Aspects of Contemporary Optics /22./. 05.09.2022-09.09.2022, Wojanow]
R&D Projects: GA MV(CZ) VJ01010035; GA MŠMT(CZ) EF16_026/0008460
Institutional support: RVO:68081731
Keywords : optical fibre * vibrations * speech * eavesdropping * transfer characteristics * speech transmission index * interferometer
OECD category: Optics (including laser optics and quantum optics)
https://psc2022.pwr.edu.pl/docs/pscoc2022_book_of_abstracts.pdf

In metrology, optical fibre links have been used for disseminating precise optical frequencies for the past two decades. Mainly for the purpose of remote optical atomic clock comparisons. The precise optical frequency is subject to shifting due to Doppler effect induced by mechanical vibrations and thermal expansion of the fibre. These shifts can be compensated using various developed servo-loop techniques. As a side effect of these efforts, the use of optical fibres in seismological sensing has been reported by several teams. With the knowledge of these phenomena, the existing optical fibre infrastructure in buildings can be misused for eavesdropping and thus pose a new security risk. In our contribution we are investigating the transfer of mechanical vibrations to the fibre in the audible frequency band. An experimental installation of optical fibre imitating typical conditions in buildings was placed into an anechoic chamber
and exposed to acoustic vibrations of defined levels and frequencies. Using a heterodyne interferometric system, the phase changes of C-band laser radiation transmitted through the fibre were detected and converted to an audio signal. The transfer characteristics of the fibre for the audible frequencies was measured. Using a special normalized test signal the Speech Transmission Index was estimated.
Permanent Link: https://hdl.handle.net/11104/0339555