The Viking age glass beads of Ireland and their North Atlantic context

Hitherto, the majority of studies which have included the discussion of Viking glass beads have mainly focused on the assemblages from individual sites, with limited use of known parallels. Exceptions to this include recent publications regarding the Icelandic material and Callmer’s 1977 catalogue of the finds from mainland Scandinavia, now over thirty years old. Analysis of these finds from Ireland was, for the most part, non-existent. The aim of this research is to address this lack of analysis within Ireland, while incorporating the wider context of the beads within the Viking North Atlantic. The research thus examines the use of glass beads of diagnostically Scandinavian manufacture and import found in Ireland, particularly in relation to their context and distribution. The history of research from Ireland as well as from across the Viking world is considered and explored throughout the thesis, with critique of methods and discussions used. Focussed analysis of both published and unpublished material detailing artefacts from Scandinavia (especially Vestfold), Britain, Iceland, the Faroe Islands and L’Anse aux Meadows is presented within the thesis in order to provide the greater picture for the core section of the thesis, the glass beads found in Ireland. Three appendices are included within Volume 2, databases of the glass beads under discussion from Ireland, the Vestfold region graves in Norway and the topsoil finds from the Kaupang trading place, also located within Vestfold. These appendices therefore represent the first-hand analysis of glass beads by the author. In total, this research represents the most up-to-date analysis of Viking glass beads from Ireland and presents a new look at the patterns of use, trade and interpersonal contact that affected the everyday lives of individuals living within Viking Age Ireland.

Biosensors using photonic crystal fibres

In this thesis, we present the unique properties of hollow-core photonic crystal fibres (HC-PCFs) for sensing applications in terms of viscosity detection and DNA sensing using a special poly(ethylene) glycol (PEGDA) hydrogel. The low loss HC-PCFs ensure a long interaction length between the sample and the optical signals. Thus in this thesis, we report the characterisation of filled HC-PCFs and the development of a selective filling process. For the first time, we report the investigation of a new viscometer device, and a new device for DNA sensing development, and also the chemical process for hydrogel growth was adapted to the fibres. By combining HC-PCFs with the hydrogel we enable 3D volumetric sample confinement within the HC-PCF, further increasing the interaction between the sample and the optical signal. However, the hydrogel has a large influence on the guidance properties of the HC-PCF and the HC-PCF has a strong influence on the growth process for the hydrogel itself. When we integrate the hydrogel and HC-PCFs we detect concentration levels as low as 400 nM of labelled DNA. However, using our technology for fluorescence detection we can achieve results two orders of magnitude better than those previously reported.

High speed optical communication systems: From modulation formats to radically new fibres

High volumes of data traffic along with bandwidth hungry applications, such as cloud computing and video on demand, is driving the core optical communication links closer and closer to their maximum capacity. The research community has clearly identifying the coming approach of the nonlinear Shannon limit for standard single mode fibre [1,2]. It is in this context that the work on modulation formats, contained in Chapter 3 of this thesis, was undertaken. The work investigates the proposed energy-efficient four-dimensional modulation formats. The work begins by studying a new visualisation technique for four dimensional modulation formats, akin to constellation diagrams. The work then carries out one of the first implementations of one such modulation format, polarisation-switched quadrature phase-shift keying (PS-QPSK). This thesis also studies two potential next-generation fibres, few-mode and hollow-core photonic band-gap fibre. Chapter 4 studies ways to experimentally quantify the nonlinearities in few-mode fibre and assess the potential benefits and limitations of such fibres. It carries out detailed experiments to measure the effects of stimulated Brillouin scattering, self-phase modulation and four-wave mixing and compares the results to numerical models, along with capacity limit calculations. Chapter 5 investigates hollow-core photonic band-gap fibre, where such fibres are predicted to have a low-loss minima at a wavelength of 2μm. To benefit from this potential low loss window requires the development of telecoms grade subsystems and components. The chapter will outline some of the development and characterisation of these components. The world's first wavelength division multiplexed (WDM) subsystem directly implemented at 2μm is presented along with WDM transmission over hollow-core photonic band-gap fibre at 2μm. References: [1]P. P. Mitra, J. B. Stark, Nature, 411, 1027-1030, 2001 [2] A. D. Ellis et al., JLT, 28, 423-433, 2010.