City Research Online

Abstract

Optical fibre sensing techniques are playing an increasingly important role in applications where precise and non-destructive measurements are required. Not only are traditional electronically based sensors being gradually replaced by their optical fibre analogues, but also the classical optical measuring devices, such as bulk optical interferometers, are being reconfigured as devices constructed from optical fibre and fibre components. On the other hand, the availability of different types of light sources with different spectral distributions, such as light emitting diodes, single mode and multimode laser diodes, opens up the possibility of widely use these sources for optical fibre sensor applications.

The main theme of this thesis is a series of investigations of the characteristics of the output from interferometric systems that use multimode laser diodes as their low coherence light sources. The multimode laser diode, developed recently in commercial quantities for use with the compact disc player, offer high light output levels in a small emitting area, which makes it the preferred choice for optical fibre sensor applications.

The discussions began with a general introduction to the thesis. In chapter 1 the principle of optical sensing by using an interferometer is introduced and an outline of the basic framework of this thesis can be seen. Based upon a new classification of the optical fibre sensing techniques, a general discussion and a review of interferometric systems using low coherence light sources are shown in chapters 3 and 4 respectively. By using a new electronic signal processing scheme, a common-mode bulk interferometer was replaced with its optical fibre analogue, which is described in chapter 5.

The main characteristics of the output intensity distribution from several types of interferometric systems which were illuminated by light from multimode laser diodes were intensively studied both theoretically and experimentally. The results of the investigation and the possible applications of using the schemes developed in this work are shown in the chapters 6 to 9. A general conclusion and suggestions for the future of the work are presented.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses School of Science & Technology > Engineering

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