Distributed acoustic systems (DAS)

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Fiber optic system comprises such main components as transmitter-receiver unit, called analyzer, fiber optic sensing cable (customized due to a specific application) and a dedicated software. Distributed acoustic system has been developed to analyze acoustic signal along the entire length of fiber, identify and localize the signal emitted by external exposure to a sensing cable. Thus DAS solution involves a numerous quantity of acoustic receivers that register acoustic signal just in one shot. The system is based on standard single-mode fibers so that the equipment could be deployed either to existing cables or connected during the installation of new fiber optic lines. A variety of specialty sensors developed by the company offers a vast range of applications in different industries.

Technical specification

Types of sensing cables

Distance range: up to 50 km

Sensor type: distributed (totally dielectric)

Frequency range: up to 100 kHz (depending on the length)

Distance resolution: from 1 m

Operating temperature : -40 °C to +60 °С

(up to 700 °C for specialty sensor)

Sensor lifetime: more than 25 years

Standard telecommunication

Specialty high-precision

Geophysical logging

Deepwater logging

Installation methods

Installed on the surface (concrete, metal, plastic)

Embedded in the soil

Embedded in concrete

Integrated in composite materials

Operating principle

When a powerful light pulse of wavelength propagates through an optical fiber, a small amount of the incident energy is backscattered in several directions due to local inhomogeneities. Scaterring process originates from material impurity that interacts with a light pulse, known as Rayleigh Scattering. The energy that is scattered back to the sensor is then returns to a photodetector which is used to measure the diffracted light and to retrieve the correct attenuated backscatter signal by convolution process. If there’s any change in amplitude of the returning Rayleigh signal, this indicates a disturbance along the optical fiber. The indicator of the external exposure is a phase difference gathered in the optical fiber between two signals. Analysis of the interferometric reflectogram enables to recreate distribution of the external exposure that causes additional phase differences with a high spatial resolution. At the same time standard methods of time calculation facilitates to accurate localization of one or another perturbation.