Analysis of distributed optical fibre acoustic sensors through numerical modelling.

A distributed optical fibre acoustic sensor is numerically modelled. To increase the flexibility of the model, the building blocks of the sensing system are modelled separately and later combined to form the numerical model. This approach is adopted to facilitate the evaluation of each of the individual building blocks and their effects on the output of the sensor.

High spatial resolution distributed optical fiber dynamic strain sensor with enhanced frequency and strain resolution.

A distributed optical fiber dynamic strain sensor with high spatial and frequency resolution is demonstrated. The sensor, which uses the ϕ-OTDR interrogation technique, exhibited a higher sensitivity thanks to an improved optical arrangement and a new signal processing procedure. The proposed sensing system is capable of fully quantifying multiple dynamic perturbations along a 5 km long sensing fiber with a frequency and spatial resolution of 5 Hz and 50 cm, respectively.

Contributed Review: Distributed optical fibre dynamic strain sensing.

Extensive research on Brillouin- and Raman-based distributed optical fibre sensors over the past two decades has resulted in the commercialization of distributed sensors capable of measuring static and quasi-static phenomena such as temperature and strain. Recently, the focus has been shifted towards developing distributed sensors for measurement of dynamic phenomena such as dynamic strain and sound waves. This article reviews the current state of the art distributed optical fibre sensors capable of quantifying dynamic vibrations.

Distributed optical fiber dynamic magnetic field sensor based on magnetostriction.

A distributed optical fiber sensor is introduced which is capable of quantifying multiple magnetic fields along a 1 km sensing fiber with a spatial resolution of 1 m. The operation of the proposed sensor is based on measuring the magnetorestrictive induced strain of a nickel wire attached to an optical fiber. The strain coupled to the optical fiber was detected by measuring the strain-induced phase variation between the backscattered Rayleigh light from two segments of the sensing fiber.

Distributed dynamic large strain optical fiber sensor based on the detection of spontaneous Brillouin scattering.

A Brillouin-based distributed optical fiber dynamic strain sensor is described which converts strain-induced Brillouin frequency shift into optical intensity variations by using an imbalanced Mach-Zhender interferometer. A 3×3 coupler is used at the output of this interferometer to permit differentiate and cross multiply demodulation. The demonstrated sensor is capable of probing dynamic strain disturbances over 2 km of sensing length every 0.

Compact acoustic sensor based on air-backed mandrel coiled with optical microfiber.

We propose and demonstrate a compact acoustic sensor comprising a 2 μm diam, 35 mm length optical microfiber coiled around a 3 mm diam air-backed mandrel. Acoustic waves induce local pressure variations that change the mandrel diameter and thus the optical path length of the mode propagating in the microfiber. The phase modulation is detected via a single-fiber polarimetric interferometer.