The speech information leakage through the fiber-optic technical channels of the office: noise control (noise reduction)

Cover Page

Cite item

Full Text

Open Access Open Access
Restricted Access Access granted
Restricted Access Subscription or Fee Access

Abstract

The efficiency of functioning and neutralization of speech information leakage channels through the fiber-optic utilities is largely determined by the noise pollution of the optical channel in the structured cabling systems of the facility. Adaptation of the well-known noise control methods in the fiber-optic speech information leakage channels allows to significantly increase the signal-to-noise ratio and, consequently, the interception efficiency. In particular, the fiber-optic subsystem of structured cabling systems at the facility with the distributed measuring properties can be represented as a phased acoustic fiber-optic array. While using the integration method for multichannel measurement, an informative signal can be isolated against the noise background. Another noise control method represents the comparison of two optical channels with asymmetric acoustic sensitivity (the differential method) that is possible due to the placement of optic fiber duplex cables in the cable ducts. The differential noise reduction method was tested on an experimental unit for investigating the speech information leakage channel that demonstrated a significant increase in the signal-to-noise ratio even at the short cable lengths. The differential method implementation is possible due to the correlation of low-frequency noise in the optical channel over a long period of time (0.1 ms) and a significant light path in the optical fiber (20 km). The given theoretical and practical studies show a high level of danger of acoustic fiber-optic speech information leakage channels and possible countermeasures.

Full Text

Restricted Access

About the authors

Vladimir V. Grishachev

Russian State University of the Humanities

Author for correspondence.
Email: grishachev@mail.ru
ORCID iD: 0000-0002-7585-7282

Cand. of Sc.(Phys.&Math.), associate professor, Institute for Information Sciences and Security Technologies (IISST)

Russian Federation, Moscow

References

  1. Buzov G. A. Zashchita informacii ogranichennogo dostupa ot utechki po tekhnicheskim kanalam. – M.: Goryachaya liniya – Telekom, 2024. 586 s. ISBN 978-5-9912-0424-8.
  2. Katorin YU.F., Razumovskij A. V., Spivak A. I. Zashchita informacii tekhnicheskimi sredstvami. – SPb: NIU ITMO, 2012. 416 s.
  3. Zajcev A.P., Shelupanov A. A., Meshcheryakov R. V. et al. Tekhnicheskie sredstva i metody zashchity informacii. – M.: OOO «Izdatel’stvo MashinostroeniE», 2009. 508 s. ISBN 978-5-94275-454-9.
  4. Khorev A. A. Tekhnicheskaya zashchita informacii. Tom 1. Tekhnicheskie kanaly utechki informacii. – M.: NPC «AnalitikA», 2008. 436 s.
  5. Khalyapin D. B. Zashchita informacii. Vas podslushivayut? Zashchishchajtes’! – M.: NOU SHO «BayarD», 2004. 432 s.
  6. Kharkevich A. A. Bor’ba s pomekhami. – M.: Librokom. Lenand.2018–280 s. – ISBN 978-5-9710-5339-2, 978-5-397-03458-6
  7. Bendat Dh., Pirsol A. Prikladnoj analiz sluchajnykh dannykh. – M.: Mir, 1989. 540 s.
  8. Kul’chin YU.N. Raspredelennye volokonno-opticheskie izmeritel’nye sistemy. – M.: FIZMATLIT. 2001. 272 s. – ISBN 978-5-9221-0072-4.
  9. Listvin A.V., Listvin V. N. Reflektometriya opticheskikh volokon. – LESARart, 2005. 208 s. ISBN 5-902367-03-4.
  10. Grishachev V.V., Kazarin O. V., Kalinina YU.D. Fizicheskaya model’ ugrozy utechki akusticheskoj (rechevoj) informacii cherez volokonno-opticheskie kommunikacii. Voprosy zashchity informacii. 2018; 3: 35–51.
  11. Grishachev V.V., Zabolockaya A. D. Problema informacionnoj bezopasnosti volokonno-opticheskikh tekhnologij. Photonics Russia. 2022; 16(6): 484–500. doi: 10.22184/1993-7296.FRos.2022.16.6.484.500.
  12. Grishachev V.V., Kalinina YU.D., Tarasov A. A. Ocenka glubiny parazitnoj modulyacii sveta v opticheskoj kabel’noj sisteme s neodnorodnostyami. Voprosy zashchity informacii. 2016; 1: 62–73.
  13. Grishachev V.V., Kazarin O. V., Kalinina YU.D. Parazitnye akusticheskie modulyacii svetovykh potokov v raz’emnykh soedineniyakh opticheskoj seti ob’ekta informatizacii. Voprosy zashchity informacii. 2018; 4: 47–56.

Supplementary files

Supplementary Files
Action
1. JATS XML
Download
2. Fig. 1. Generalized structure of an acoustic fiber-optic speech information leakage channel. An office (I) with a dedicated room (II) in a building (III) with a threat from an external intruder (IV): 1 – premises with a speech information source, 2 – fiber-optic communications, 3 – optical inhomogeneities in the cable system under direct (a) and structural (b) influences generating the parasitic modulations of light flows, 4 – optical splitter of a standard SCS (a) and the intruder’s methods (b), 5 – the intruder’s TI means [10]

Download (119KB)
Indexing metadata
3. Fig. 2. Physical noise control principles based on autocorrelation of low-frequency noise. 1 – optical fiber, 2 – probing optical pulse, 3 – noise source, 4 – optical inhomogeneity generating an optical noise signal, 5 – optical noise signal over time t and at a distance L at the speed of light c and refractive index in the fiber n

Download (48KB)
Indexing metadata
4. Fig. 3. Generalized scheme of differential probing: 1 – optical fiber, 2 – probing optical pulse, 3 – sound source, 4 – test point of the optical fiber having optical inhomogeneity with the increased acoustic sensitivity, 5 – control point of optical fiber

Download (31KB)
Indexing metadata
5. Fig. 4. Differential probing structure by the optical reflectometry methods: A – reflectometer with a system for real-time reflectogram analysis and an acoustic output, B – optical fiber with the points for an information signal generation (1) and a noise signal generation (2), C – reflectogram of an optical fiber, D – time chart of the optical pulse propagation

Download (66KB)
Indexing metadata
6. Fig. 5. Differential probing structure in the transmitted light of a duplex cable with an asymmetric optical inhomogeneity: 1 – optical transceivers, 2 – duplex fiber-optic cable, 3 – optical inhomogeneity (insert), 4 – sound source, 5 – background noise of the environment

Download (50KB)
Indexing metadata
7. Fig. 6. Experimental setup for differential probing of a fiber-optic insert in the transmitted light flux: 1 – computer with a spectrum analyzer and an audio signal source, 2 – laser, 3 – speaker and microphone in a small-sized soundproof chamber, 4 – optical feed-through adapter SC-SC, 5 – optical splitter 50/50, 6, 7 – photodetectors (photodiodes), 8 – differential amplifier, 9 – selective nanovoltmeter (amplifier) of UNIPAN type, 10 – headphones, 11 – digital oscilloscope, 12 – computer with a spectrum analyzer

Download (65KB)
Indexing metadata
8. Fig. 7. Speech information confidentiality threat model based on the TILC with a differential noise suppression method in the optical circuit on the opposite passage of standard optical flows through a duplex fiber-optic cable: 1 – speech information source, 2 – fiber-optic insert, 3 – workstation with a media converter, 4 – duplex cable, 5 – transmission direction, 6 – intruder with the TI means

Download (71KB)
Indexing metadata

Copyright (c) 2025 Grishachev V.V.