Numerically optimized implementations, mitigation and simulations of polarisation mode dispersion in real-time transmission systems

The aim of this thesis is to present numerical investigations of the polarisation mode dispersion (PMD) effect. Outstanding issues on the side of the numerical implementations of PMD are resolved and the proposed methods are further optimized for computational efficiency and physical accuracy. Methods for the mitigation of the PMD effect are taken into account and simulations of transmission system with added PMD are presented. The basic outline of the work focusing on PMD can be divided as follows. At first the widely-used coarse-step method for simulating the PMD phenomenon as well as a method derived from the Manakov-PMD equation are implemented and investigated separately through the distribution of a state of polarisation on the Poincaré sphere, and the evolution of the dispersion of a signal. Next these two methods are statistically examined and compared to well-known analytical models of the probability distribution function (PDF) and the autocorrelation function (ACF) of the PMD phenomenon. Important optimisations are achieved, for each of the aforementioned implementations in the computational level. In addition the ACF of the coarse-step method is considered separately, based on the result which indicates that the numerically produced ACF, exaggerates the value of the correlation between different frequencies. Moreover the mitigation of the PMD phenomenon is considered, in the form of numerically implementing Low-PMD spun fibres. Finally, all the above are combined in simulations that demonstrate the impact of the PMD on the quality factor (Q=factor) of different transmission systems. For this a numerical solver based on the coupled nonlinear Schrödinger equation is created which is otherwise tested against the most important transmission impairments in the early chapters of this thesis.

Vector solitons with slowly evolving states of polarisation

We demonstrate experimentally and study theoretically new type of stable pulse structures in erbium-doped fibre lasers - slowly polarisation evolving vector solitons. Demonstrated vector solitons precess with characteristic times of 100-1000 round trips and their trajectories form a double semicircle on the Poincaré sphere. © 2012 Optical Society of America.

La critique du nationalisme de la "Semaine Sociale de Bordeaux" à la "Lutte pour la civilisation et la philosophie de la paix"

Over a long period the philosopher, Maurice Blondel, was an outspoken critic of exaggerated nationalism. The series of articles that appeared in 1909-10 in the Annales de philosophie chrétienne under the title of « La Semaine sociale de Bordeaux », and later were published in book form, contained a philosophically and theologically motivated critique of the early support shown by French Catholics for the doctrinaire nationalism of Charles Maurras. In 1928 Blondel returned to a critique of this same nationalism in his detailed article « Patrie et Humanité ». But the further criticism of nationalism contained in parts of his book Lutte pour la civilisation et philosophie de la paix, which was published in 1939 (and anew in 1947 in a slightly revised edition), was of a different order, being focused on the nationalism associated with what Blondel termed totalitarisme in its then German or Nazi form. Despite this record, it would be a mistake to assume that Blondel was an internationalist fitting clearly into the Briand mould. After the First World War Blondel favoured the hard-line foreign policy advocated by Poincaré and Foch, in particular over the future of the Rhineland. And he remained a conservative Catholic. His book of 1939 denounced not only totalitarisme in both its Nazi and Soviet forms, but also, on an opposing front, liberalism in the social and economic sphere. As to the deleterious effect of nationalism on international relations, he was an advocate of strengthening international law, notably the corpus of law emanating from The Hague. Maurice Blondel was greatly admired by Robert Schuman, the prominent French foreign minister under the Fourth Republic and a key figure for post-war European integration.

A new fast generalized sphere decoding algorithm in MIMO systems

A new generalized sphere decoding algorithm is proposed for underdetermined MIMO systems with fewer receive antennas N than transmit antennas M. The proposed algorithm is significantly faster than the existing generalized sphere decoding algorithms. The basic idea is to partition the transmitted signal vector into two subvectors x and x with N - 1 and M - N + 1 elements respectively. After some simple transformations, an outer layer Sphere Decoder (SD) can be used to choose proper x and then use an inner layer SD to decide x, thus the whole transmitted signal vector is obtained. Simulation results show that Double Layer Sphere Decoding (DLSD) has far less complexity than the existing Generalized Sphere Decoding (GSDs).

A sphere of resonance for networked learning in the ‘non-places’ of our universities

The logic of ‘time’ in modern capitalist society appears to be a fixed concept. Time dictates human activity with a regularity, which as long ago as 1944, George Woodcock referred to as The Tyranny of the Clock. Seventy years on, Hartmut Rosa suggests humans no longer maintain speed to achieve something new, but simply to preserve the status quo, in a ‘social acceleration’ that is lethal to democracy. Political engagement takes time we no longer have, as we rush between our virtual spaces and ‘non-places’ of higher education. I suggest it’s time to confront the conspirators that, in partnership with the clock, accelerate our social engagements with technology in the context of learning. Through Critical Discourse Analysis (CDA) I reveal an alarming situation if we don’t. With reference to Bauman’s Liquid Modernity, I observe a ‘lightness’ in policy texts where humans have been ‘liquified’ Separating people from their own labour with technology in policy maintains the flow of speed a neoliberal economy demands. I suggest a new ‘solidity’ of human presence is required as we write about networked learning. ‘Writing ourselves back in’ requires a commitment to ‘be there’ in policy and provide arguments that decelerate the tyranny of time. I am though ever-mindful that social acceleration is also of our own making, and there is every possibility that we actually enjoy it.