Ultra-long haul optical fibre transmission systems

This thesis examines experimentally options for optical fibre transmission over oceanic distances. Its format follows the chronological evolution of ultra-long haul optical systems, commencing with opto-electronic regenerators as repeaters, progressing to optically amplified NRZ systems and finally solitonic propagation. In each case recirculating loop techniques are deployed to simplify the transmission experiments. Advances in high speed electronics have allowed regenerators operating at 10 Gbit/s to become a practical reality. By augmenting such devices with optical amplifiers it is possible to greatly enhance the repeater spacing. Work detailed in this thesis has culminated in the propagation of 10 Gbit/s data over 400,000 km with a repeater spacing of 160 km. System reliability and robustness are enhanced by the use of a directly modulated DFB laser transmitter and total insensitivity of the system to the signal state of polarisation. Optically amplified ultra-long haul NRZ systems have taken on particular importance with the impending deployment of TAT 12/13 and TPC 5. The performance of these systems is demonstrated to be primarily limited by analogue impairments such as the accumulation of amplifier noise, polarisation effects and optical non-linearities. These degradations may be reduced by the use of appropriate dispersion maps and by scrambling the transmitted state of signal polarisation. A novel high speed optically passive polarisation scrambler is detailed for the first time. At bit rates in excess of 10 Gbit/s it is shown that these systems are severely limited and do not offer the advantages that might be expected over regenerated links. Propagation using solitons as the data bits appears particularly attractive since the dispersive and non-linear effects of the fibre allow distortion free transmission. However, the generation of pure solitons is difficult but must be achieved if the uncontrolled transmission distance is to be maximised. This thesis presents a new technique for the stabilisation of an erbium fibre ring laser that has aUowed propagation of 2.5 Gbit/s solitons to the theoretical limit of ~ 18,000 km. At higher bit rates temporal jitter becomes a significant impairment and to aUow an increase in the aggregate line rate multiplexing in both time and polarisation domains has been proposed. These techniques are shown to be of only limited benefit in practical systems and ultimately some form of soliton transmission control is required. The thesis demonstrates synchronous retiming by amplitude modulation that has allowed 20 Gbit/s data to propagate 125,000 km error free with an amplifier spacing approaching the soliton period. Ultimately the speed of operation of such systems is limited by the electronics used and, thus, a new form of soliton control is demonstrated using all optical techniques to achieve synchronous phase modulation.

Transglutaminase treatment of wool fabrics leads to resistance to detergent damage

Biological detergents are now routinely used in domestic laundry because the enzymes they contain provide the added benefit of low temperature washes with improved cleaning performance. One of the key enzymes found in these detergents are proteases, which if exposed to natural protein fibres such as wool or silk can cause irreversible damage, leading to loss of fabric strength, shape and poor colour fastness. Transglutaminases (TGases) are protein cross-linking enzymes capable of adding tensile strength to wool proteins, and as a consequence are capable of remediating the damage caused by previous chemical treatments, and more importantly, by proteases. In this paper we treated dyed wool fabric with TGase and then washed the fabric with biological and non-biological detergents to investigate whether TGases would protect wool garments from damage by the undue use of biological detergents in domestic laundry. We demonstrate using different cycles of detergent washes containing biological and non-biological detergents and different TGase treatments, that wool fabric treated previously with TGase release less dye into the washing liquor and in addition maintain fabric strength at levels greater than the washed controls. As a consequence, wool garments previously treated with TGase are likely to have increased resistance to domestic washing and thus provide increased longevity. © 2005 Elsevier B.V. All rights reserved.

Lobe formation and division in the foliose lichen Xanthoparmelia conspersa

New lobe development and lobe division was studied in the foliose lichen Xanthoparmelia conspersa (Ehrh. ex. Ach.) Hale. In thalli with either the centre or margin removed, the inside edge of the perimeter, the outer edge of the reproductive centre, and fragments derived from the thallus perimeter all regenerated growing points (‘lobe primordia’) within a year. Thalli possessing isidia had the greatest ability to regenerate growing points. In reproductive thalli, there was a positive correlation between the density of new growing points and thallus size. When fragments were cut from the perimeters of mature X. conspersa thalli and glued to pieces of slate, the ratio of growing points to mature lobes increased over 54 months. Lobes within a thallus exhibited different degrees of bifurcation. In some bifurcating lobes, the point of origin of the bifurcation advanced at the same rate as the lobe tips over 4 months but in most lobes, the bifurcation point either advanced less rapidly than the lobe tips or retreated from its original location. Removing adjacent lobes had no significant effect on the radial growth of a lobe over 4 months or on the location of the bifurcation point but it increased the number of growing points. These results suggest that for X. conspersa: 1) all portions of of thalli can regenerate growing points, 2) few growing points actually develop into mature lobes, 3) individual lobes within a thallus grow and divide differently, and 4) adjacent lobes inhibit the development of growing points on their neighbours.

Transmission of non-uniform OTDM channels in nonlinearly-guided dispersion-managed fibre system

The effects of channel inequality on nonlinear signal switching in a nonlinear optical fiber loop mirror (NOLM) were investigated. It was found that the channel-to-channel amplitude differences in optical time division multiplexing (OTDM) have strong impact on swiching behavior of individual channels in a 2R regenerator. The optical pulses in different channels face either suppression of the amplitude noise or increase in noise, depending on the inter-channel amplitude difference. It was stated that appropriate control of the channel uniformity in the OTDM transmitters is required to support stable long-haul transmission in 2R regenerated systems.

Demonstration and characterisation of a non-inverting all-optical read/write regenerative memory

An all-optical regenerative memory device using a single loop mirror and a semiconductor optical amplifier is experimentally demonstrated. This configuration has potential for a low power all-optical stable memory device with non-inverting characteristics where packets are stored by continuously injecting the regenerated data back into the loop.

Novel synchronous DPSK optical regenerator based on a feed-forward based carrier extraction scheme

We experimentally demonstrate a novel synchronous 10.66Gbit/s DPSK OEO regenerator which uses a feed-forward carrier extraction scheme with an injection-locked laser to synchronize the regenerated signal wavelength to the incoming signal wavelength. After injection-locking, a low-cost DFB laser used at the regenerator exhibited the same linewidth characteristics as the narrow line-width transmitter laser. The phase regeneration properties of the regenerator were evaluated by emulating random Gaussian phase noise applied to the DPSK signal before the regenerator using a phase modulator driven by an arbitrary waveform generator. The overall performance was evaluated in terms of electrical eye-diagrams, BER measurements, and constellation diagrams.

Evolution of timing jitter in nonlinearly-guided, dispersion managed transmission systems

Timing jitter is a major factor limiting the performance of any high-speed, long-haul data transmission system. It arises from a number of reasons, such as interaction with accumulated spontaneous emission, inter-symbol interference (ISI), electrostriction etc. Some effects causing timing jitter can be reduced by means of non-linear filtering, using, for example, a nonlinear optical loop mirror (NOLM) [1]. The NOLM has been shown to reduce the timing jitter by suppressing the ASE and by stabilising the pulse duration [2, 3]. In this paper, we investigate the dynamics of timing jitter in a 2R regenerated system, nonlinearly guided by NOLMs at bit rates of 10, 20, 40, and 80- Gbit/s. Transmission performance of an equivalent non-regenerated (generic) system is taken as a reference.

Dimethylsulfoxide oxidizes glutathione in vitro and in human erythrocytes:kinetic analysis by 1H NMR

The interaction of dimethylsulfoxide (Me2SO) with glutathione was investigated under non-equilibrium conditions in solution using 1H NMR and in intact erythrocytes using 1H spin-echo NMR. In solution the reaction was observed to follow second-order kinetics (Rate = k1[glutathione][Me2SO]) at 300 K pH 7.4, ksol = 4.7 × 10-5 mol -1 L1 s-1. In intact erythrocytes the rate constant for the cellular environment, kcell, was found to be slightly larger at 8.1 × 10-5 mol-1 L1 s-1. Furthermore, the reaction of Me2SO with erythrocyte glutathione showed a biphasic dependence on the Me2SO concentration, with little oxidation of glutathione occurring until the Me2SO concentration exceeded 0.5 mol L-1. The results suggest that at lower concentrations, Me2SO can be effectively removed, most probably by reaction with glutathione, which is regenerated by glutathione reductase, although preferential reaction with other cellular components (e.g., membrane or cellular thiols) cannot be ruled out. Thus the concentrations of Me2SO that are commonly used in cryopreservation of mammalian cells (∼1.4 mol L-1) can cause oxidation of intracellular glutathione.

Study of EEPN mitigation using modified RF pilot and Viterbi-Viterbi based phase noise compensation

We propose - as a modification of the optical (RF) pilot scheme -a balanced phase modulation between two polarizations of the optical signal in order to generate correlated equalization enhanced phase noise (EEPN) contributions in the two polarizations. The method is applicable for n-level PSK system. The EEPN can be compensated, the carrier phase extracted and the nPSK signal regenerated by complex conjugation and multiplication in the receiver. The method is tested by system simulations in a single channel QPSK system at 56 Gb/s system rate. It is found that the conjugation and multiplication scheme in the Rx can mitigate the EEPN to within 1/2 orders of magnitude. Results are compared to using the Viterbi-Viterbi algorithm to mitigate the EEPN. The latter method improves the sensitivity more than two orders of magnitude. Important novel insight into the statistical properties of EEPN is identified and discussed in the paper. © 2013 Optical Society of America.

Radical intermediates in chloroform reactions over triphenylphosphine-protected Au nanoparticles

Reactions of chloroform over triphenylphosphine-protected Au nanoparticles have been studied using electron paramagnetic resonance (EPR) spectroscopy and a spin trapping technique. Two competing reactions, abstraction of hydrogen and halogen atoms, were identified. The hydrogen abstraction reaction showed an inverse kinetic isotope effect. Treatment of nanoparticles with oxidizing or reducing reagents made it possible to tune the selectivity of radical formation from halogen to hydrogen (deuterium) abstraction. Treatment with PbO2 promoted the deuterium abstraction reaction followed by the loss of nanoparticle activity, whereas treatment with NaBH4 regenerated the nanoparticle activity towards Cl atom abstraction. X-ray photoelectron spectroscopy showed an increased Au:P ratio upon treatment with oxidizing reagents. This is likely due to the oxidation of some phosphine ligands to phosphine oxides which then desorb from the nanoparticle surface. © 2009 The Royal Societ of Chemistry.

Cooling of greenhouses using seawater:a solar driven liquid-desiccant cycle for greenhouse cooling in hot climates

Evaporative pads are frequently used for the cooling of greenhouses. However, a drawback of this method is the consumption of freshwater. In this paper it is shown, both theoretically and through a practical example, that effective evaporative cooling can be achieved using seawater in place of fresh water. The advantages and drawbacks of using seawater are discussed more generally. In climates that are both hot and humid, evaporative systems cannot always provide sufficient cooling, with the result that cultivation often has to be halted during the hottest months of the year. To overcome this, we propose a concept in which a desiccant pad is used to dehumidify the air before it enters the evaporative pad. The desiccant pad is supplied with a hygroscopic liquid that is regenerated by the energy of the sun. The performance of this concept has been modelled and the properties of various liquids have been compared. An attractive option is to obtain the liquid from seawater itself, given that seawater contains hygroscopic salts such as magnesium chloride. Preliminary experiments are reported in which magnesium chloride solution has been regenerated beneath a solar simulator.

Using a systems approach in logistics design and planning

The international economic and business environment continues to develop at a rapid rate. Increasing interactions between economies, particularly between Europe and Asia, has raised many important issues regarding transport infrastructure, logistics and broader supply chain management. The potential exists to further stimulate trade provided that these issues are addressed in a logical and systematic manner. However, if this potential is to be realised in practice there is a need to re-evaluate current supply chain configurations. A mismatch currently exists between the technological capability and the supply chain or logistical reality. This mismatch has sharpened the focus on the need for robust approaches to supply chain re-engineering. Traditional approaches to business re-engineering have been based on manufacturing systems engineering and business process management. A recognition that all companies exist as part of bigger supply chains has fundamentally changed the focus of re-engineering. Inefficiencies anywhere in a supply chain result in the chain as a whole being unable to reach its true competitive potential. This reality, combined with the potentially radical impact on business and supply chain architectures of the technologies associated with electronic business, requires organisations to adopt innovative approaches to supply chain analysis and re-design. This paper introduces a systems approach to supply chain re-engineering which is aimed at addressing the challenges which the evolving business environment brings with it. The approach, which is based on work with a variety of both conventional and electronic supply chains, comprises underpinning principles, a methodology and guidelines on good working practice, as well as a suite of tools and techniques. The adoption of approaches such as that outlined in this paper helps to ensure that robust supply chains are designed and implemented in practice. This facilitates an integrated approach, with involvement of all key stakeholders throughout the design process.

Abnormal spectral evolution of fiber Bragg gratings in hydrogenated fibers

The properties of fiber Bragg gratings in hydrogenated fibers under conditions of ultraviolet overexposure were investigated. Abnormal spectral evolution of the regenerated grating following erasure of the initial type I grating was observed in the hydrogenated fibers. The regenerated grating also exhibited less temperature sensitivity and an 18 nm shift in the Bragg wavelength.

ASPICO: Advanced Scientific Portal for International Cooperation on Digital Cultural Conten

* This research is partially supported by a grant (bourse Lavoisier) from the French Ministry of Foreign Affairs (Ministère des Affaires Etrangères).

Xinjiang and Central Asia: Ethno-religious, political, and economic interactions

The neighboring regions of Xinjiang and Central Asia, linked historically on the famous Silk Road, later developed separately as a result of the incorporation of the former into China and the latter into the Russian Empire and Soviet Union. Thus, interaction between Xinjiang and Central Asia has been constrained by the nature of the Sino-Russian or Sino-Soviet relationship. However, the demise of the Soviet Union--which resulted in the independence of five Central Asian states--and the recent economic reforms in the People's Republic of China suggest dramatic new possibilities for interregional cooperation.^ In this thesis, an historical and comparative approach is employed to study Chinese policies in Xinjiang and Soviet policies in Central Asia, and concludes that despite several decades of separate development, the common ethnic and religious origins of the indigenous peoples and their former ties will facilitate greater interaction between the two regions. ^