The development of fibre-optic interferometric sensor arrays for application in underwater acoustics has been an area of active research since the late 1970's. The technology has reached a level whereby prototype arrays have been successfully demonstrated in sea-trials. However, the recent development of several new technologies may significantly increase the size and performance of these arrays. We demonstrate the potential increase in multiplexed array sizes using architectures based on combining dense wavelength division multiplexing and time division multiplexing. These architectures also include erbium doped fibre amplifiers for post, pre, inline and remote amplification in order to increase the standoff distance between the array and electronics unit. We also theoretical investigate the limitations imposed on the number of sensors that can be multiplexed, due to nonlinear transmission effects in the link fibre in the presence of high optical powers and multiple wavelengths. We also demonstrate novel DFB erbium doped fibre lasers as optical sources. These sources exhibit linewidths significantly narrower than semiconductor DFB lasers, which are currently used in many sensor arrays, and thus may provide a significant improvement in sensor resolution. We investigate the intensity and frequency noise properties of these lasers, their modulation properties and successfully develop intensity noise and frequency noise reduction techniques. We also investigate the potential of fibre-optic acoustic vector sensors and demonstrate fibre-optic flexural disk accelerometers. Finally, we demonstrate polymer coated in-fibre Bragg gratings as pressure and temperature sensors and investigate polymer coatings as a means to increase the acoustic responsivity of fibre laser acoustic sensors.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:394987 |
| Date | January 2001 |
| Creators | Cranch, Geoffrey Alan |
| Publisher | Heriot-Watt University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10399/1197 |
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