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Development of an optical fibre multiplexed Bragg grating strain measurement system

Kemp, J. (1998). Development of an optical fibre multiplexed Bragg grating strain measurement system. (Unpublished Doctoral thesis, City, University of London)


Strain sensing continues to be an area of research interest due to its importance in a variety of fields including civil, mechanical and aerospace engineering. This has intensified with the advent of the concept of ‘smart structures’, i.e. structures that possess both the means to detect changes in their environment and the ability to respond to those changes. Strain measurement techniques using optical fibre based sensors have attracted a great deal of interest due to the advantages afforded by the nature of the fibres themselves in such measurement systems.

This thesis represents a body of work concerning the design, development and analysis of an optical fibre based strain sensor system, utilizing Bragg gratings as the prime sensing elements.

Wavelength demodulation is examined and a wavelength shift detection scheme utilizing a Wollaston prism interferometer is presented having been considered as a means to achieve wavelength demodulation in sensor systems. However, further analysis suggested an alternative was needed and the final wavelength demodulation scheme chosen, based on the Michelson interferometer, is analysed in this context.

A time-domain based demultiplexing system is presented where the signals from individual Bragg gratings are separated electronically by using a matrix of fast GaAs switches. This system is successfully demonstrated and the capability of addressing a potentially large number of Bragg gratings sensors elements is considered. Results are presented in the form of strain and temperature sensitivity data and an analysis of the results in the frequency domain demonstrates that the crosstalk present in the system is very low.

The results presented are set in the context of work reported in the literature and in the light of results achieved elsewhere.

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