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Title: Design and application of a distributed optical fibre dynamic strain sensor
Author: Masoudi, Ali
ISNI:       0000 0004 5364 1055
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2015
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Over the past two decades, distributed optical fibre sensors (DOFS) based on Brillouin and Raman scattering have been extensively studied. As a result, a wide range of distributed temperature and strain sensors with different sensing range and accuracy levels have been developed. However, due to the weak nature of Brillouin and Raman scattering, most of the research in this field has been focused on DC or quasi-DC measurement of temperature and strain. On the other hand, the Rayleigh-based DOFS which have been previously proposed are only able to detect dynamic disturbances along the sensing fibre. In this thesis, a new sensing technique has been developed which is capable of quantifying and tracking multiple dynamic perturbations along the sensing fibre, simultaneously. The sensing mechanism of the proposed technique relies on the phase of the Rayleigh backscattered light. For any given segment along the fibre, the difference in the phase of the backscattered light radiating from the two ends of that segment changes as a function of the external perturbations at that segment. Therefore, dynamic vibration along the sensing fibre can be extracted by comparing the phase of the backscattered light from two different sections of the sensing fibre. By implementing this technique using an imbalanced Mach-Zehnder Interferometer (IMZI), a distributed sensor was developed that was capable of quantifying dynamic perturbations within the frequency range of 200Hz ~5kHz along a 1km sensing fibre. Furthermore, the same principle was used to develop a distributed magnetic field sensor. By coupling an optical fibre to a magnetostrictive wire and by using this combination as a magnetic field to strain transducer, a distributed magnetic field sensor was formed with magnetic intensity range of 1Gs~ 8Gs and frequency range of 50Hz ~5kHz. In addition, the IMZI arrangement was used as a frequency-to-intensity convertor to develop a distributed dynamic strain sensor based on Brillouin scattering. The proposed sensor exhibited a strain range of 400µέ 4mέ and a sensing range of 2km.
Supervisor: Newson, Trevor Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics ; TK Electrical engineering. Electronics Nuclear engineering