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Title: Ultralow loss and wide bandwidth hollow-core photonic bandgap fibres for telecom applications
Author: Numkam Fokoua, Eric Rodrigue
ISNI:       0000 0004 5367 405X
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2015
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Light guidance in air has significant potential in diverse photonics applications, one of hich is optical communications where it may be key to achieving lower attenuation and optical nonlinearity than in conventional silica fibres. This thesis presents research conducted as part of the EU FP7 project MODEGAP, and is concerned with the design of hollow-core photonic bandgap fibres (HC-PBGFs) with low loss and wide bandwidths suitable for high capacity data transmission. In these fibres, loss is dominated by scattering from surface roughness and is subject to the design of the fibre cross-section. Using the criterion of reduced guided mode-field intensity at the interfaces, we conduct detailed finite element simulations which allow to identify preferable structures. A theory of light scattering from surface roughness in HC-PBGFs is then derived, and expressions are obtained which combine statistical information on the roughness and the guided mode-field overlap with scattering surfaces to predict the far-field scattering pattern and the fibre loss. A model based on mass conservation is proposed to predict the properties of HC-PBGFs from knowledge of the preforms from which they are made, and this in turn allows optimizing the design of such preforms. A method allowing accurate modelling of fabricated HC-PBGFs from scanning electron micrographs of their cross-sections is devised and such simulations indicate that structural distortions in the fibre cross-section cause higher field intensities near the interfaces, and hence higher losses. Systematic studies of distortions are then conducted, and it is found that not all distortions are equally detrimental. Combining these findings and using realistic estimates, a HC-PBGF design with 37 cell core defect and loss as low as 0.2dB/km over 580nm of bandwidth near the wavelength of 2μm is presented.
Supervisor: Richardson, David 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