Distributed optical fibre acoustic sensors – future applications in audio and acoustics engineering

Abstract

First successful experiments with optical fibre acoustic sensors were performed in 1970s by Bucaro et al.1 and Cole et al.2. Those and later developments were primarily concerned with point sensors which are equivalent to single microphone or a microphone array with fixed number of microphone. Optical fibre acoustic sensors utilise pressure induced variations in the refractive index of the fibre and its geometrical deformation caused by flexural wave to measure acoustic disturbance3.
Single point optical fibre acoustic sensors are usually more expensive than microphones. However, if a large number of sensors is needed, distributed optical fibre sensors can offer a cost-effective alternative to microphone array due to the possibility of mapping the sound pressure level as a function of distance. Historically the oldest application of distributed optical fibre sensors (DOFS) were to measure the integrity of optical fibres along long telecom optical links. Just recently the focus has shifted towards distributed measurements of sound and vibration4.
This paper briefly reviews the optical fibre distributed acoustic sensor technology. First, we look into distributed sensing principles in more details and compare different methods. In the next section,we will discuss the principle of Phase Optical Time Domain Reflectometry (phi-OTDR) and Rayleigh backscattering, which is used in the system designed and built by Masoudi et al.5. We will discuss the limitations of the system from acoustics point of view. Then, we propose possible applications of such a system in acoustic measurements. In sections 4–6, the results of the preliminary experiment performed in a reverberation chamber are presented and discussed.

More information

Identifiers

ORCID for Ali Masoudi: orcid.org/0000-0003-0001-6080

ORCID for Keith Holland: orcid.org/0000-0001-7439-2375

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