Fiber optic infrastructure is essential in the transmission of data of all kinds, both for the long haul and shorter distances in cities. Optical fibers are also preferred for data infrastructures inside buildings, especially in highly secured organizations and government facilities. This paper focuses on a reference measurement and analysis of optical fiber cables sensitivity to acoustic waves. Measurement was carried out in an anechoic chamber to ensure stable conditions of acoustic pressure in the range from 20 Hz to 20 kHz. The frequency response, the signal-to-noise ratio per frequency, and the Speech Transmission Index are evaluated for various types of optical fiber cables and different ceiling tiles, followed by their comparison. The influence of the means of fixing the cable is also studied. The results prove that optical fiber-based infrastructure in buildings can be exploited as a sensitive microphone.

Department of Telecommunications Brno University of Technology FEEC Technicka 12 616 00 Brno Czech Republic

Institute of Scientific Instruments of the Czech Academy of Sciences Královopolská 147 612 64 Brno Czech Republic

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Distributed Acoustic Sensing of Sounds in Audible Spectrum in Realistic Optical Cable Infrastructure