All-optical passive quasi-regeneration in transoceanic 40 Gbit/s return-to-zero transmission systems with strong dispersion management

A method of all-optical passive quasi-regeneration in transoceanic 40 Gbit/s return-to-zero transmission systems with strong dispersion management was described. The use of in-line nonlinear optical loop mirrors (NOLM) by the method was demonstrated. The quasi-regeneration of signals performed by NOLMs was found to improve the systems's performance.

Stable propagation of solitons with increased energy through the combined action of dispersion management and periodic saturable absorption

It is shown, through numerical simulations, that by using a combination of dispersion management and periodic saturable absorption it is possible to transmit solitonlike pulses with greatly increased energy near to the zero net dispersion wavelength. This system is shown to support the stable propagation of solitons over transoceanic distances for a wide range of input powers.

Dispersion-managed solitons: a new paradigm for high data rate

The WDM properties of dispersion managed (DM) solitons and the reduction in Gordon-Haus jitter means that it is possible to contemplate multiple channels each at 10 Gbit/s for transoceanic distances without the need for elaborate soliton control. This paper will concentrate on fundamental principles of DM solitons, but will use these principles to indicate optimum maps for future high-speed soliton systems.

Numerical modelling of dispersion managed soliton transmission

This thesis presents the results of numerical modelling of the propagation of dispersion managed solitons. The theory of optical pulse propagation in single mode optical fibre is introduced specifically looking at the use of optical solitons for fibre communications. The numerical technique used to solve the nonlinear Schrödinger equation is also introduced. The recent developments in the use of dispersion managed solitons are reviewed before the numerical results are presented. The work in this thesis covers two main areas; (i) the use of a saturable absorber to control the propagation of dispersion managed solutions and (ii) the upgrade of the installed standard fibre network to higher data rates through the use of solitons and dispersion management. Saturable absorbe can be used to suppress the build up of noise and dispersive radiation in soliton transmission lines. The use of saturable absorbers in conjunction with dispersion management has been investigated both as a single pulse and for the transmission of a 10Gbit/s data pattern. It is found that this system supports a new regime of stable soliton pulses with significantly increased powers. The upgrade of the installed standard fibre network to higher data rates through the use of fibre amplifiers and dispersion management is of increasing interest. In this thesis the propagation of data at both 10Gbit/s and 40Gbit/s is studied. Propagation over transoceanic distances is shown to be possible for 10Gbit/s transmission and for more than 2000km at 40Gbit/s. The contribution of dispersion managed solitons in the future of optical communications is discussed in the thesis conclusions.

Dispersion-managed solitons: a new paradigm for high data rate

The WDM properties of dispersion managed (DM) solitons and the reduction in Gordon-Haus jitter means that it is possible to contemplate multiple channels each at 10 Gbit/s for transoceanic distances without the need for elaborate soliton control. This paper will concentrate on fundamental principles of DM solitons, but will use these principles to indicate optimum maps for future high-speed soliton systems.

Stable propagation of solitons with increased energy through the combined action of dispersion management and periodic saturable absorption

It is shown, through numerical simulations, that by using a combination of dispersion management and periodic saturable absorption it is possible to transmit solitonlike pulses with greatly increased energy near to the zero net dispersion wavelength. This system is shown to support the stable propagation of solitons over transoceanic distances for a wide range of input powers.

The use of microviscometry to study polymer dissolution from solid dispersion drug delivery systems

Solid dispersions can be used to improve dissolution of poorly soluble drugs and PVP is a common polymeric carrier in such systems. The mechanisms controlling release of drug from solid dispersions are not fully understood and proposed theories are dependent on an understanding of the dissolution behaviour of both components of the dispersion. This study uses microviscometry to measure small changes in the viscosity of the dissolution medium as the polymer dissolves from ibuprofen-PVP solid dispersions. The microviscometer determines the dynamic and kinematic viscosity of liquids based on the rolling/falling ball principle. Using a standard USP dissolution apparatus, the dissolution of the polymer from the solid dispersion was easily measured alongside drug release. Drug release was found to closely follow polymer dissolution at the molecular weights and ratios used. The combination of sensitivity and ease of use make microviscometry a valuable technique for the elucidation of mechanisms governing drug release from polymeric delivery systems. © 2004 Elsevier B.V. All rights reserved.

Systems biology approach to study permeability of paracetamol and its solid dispersion

Physiological changes that take place at cellular level are usually reflective of their level of gene expression. Different formulation excipients have an impact on physiological behavior of the exposed cells and in turn affect transporter genes, enterocyte-mediated metabolism and toxicity biomarkers. The aim of this study was to prepare solid dispersion of paracetamol and evaluate genetic changes that occur in Caco-2 cell lines during the permeability of paracetamol alone and paracetamol solid dispersion formulations. Paracetamol-PEG 8000 solid dispersion was prepared by melt fusion method and the formulation was characterised using differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Formulation of solid dispersion resulted in the conversion of crystalline drug into an amorphous form. Permeability studies showed that paracetamol absorption was higher from the solid dispersion formulation. DNA microarrays analysis was carried out in order to investigate the involvement of any efflux/uptake transporters in paracetamol or its solid dispersion permeability. Neither transporter carriers nor efflux proteins were found to be involved in the absorption of paracetamol or its PEG solid dispersion. Gene expression analysis established that paracetamol toxicity was potentially reduced upon formulation into solid dispersion when ATP binding cassette (ABC) and solute carrier transporter (SLC) genes were analyzed.

Polarisation mode dispersion induced transmission penalties for long-haul high speed optical communication systems

Results of full numerical simulations of a guiding-centre soliton system with randomly birefringent SMF fibre are shown and analysed. It emerges that the soliton system becomes unstable even for small amounts of PMD.

Simulation of guiding-centre soliton transmission system stability in the presence of polarisation mode dispersion

Results of full numerical simulations of a guiding-centre soliton system with randomly birefringent SMF fibre are shown and analysed. It emerges that the soliton system becomes unstable even for small amounts of PMD.

Polarisation mode dispersion correlations with the coarse-step method

Having a fixed differential-group delay (DGD) term b′ in the coarse-step method results in a repetitive pattern in the autocorrelation function (ACF). We solve this problem by inserting a varying DGD term at each integration step. Furthermore we compute the range of values needed for b′ and simulate the phenomenon of polarisation mode dispersion for different statistical distributions of b′. We examine systematically the modified coarse-step method compared to the analytical model, through our simulation results. © 2006 Elsevier B.V. All rights reserved.

Tunable compensation of second and third order dispersion by non-uniformly strained chirped fibre Bragg grating

A novel fibre grating device is demonstrated with tuneable chromatic dispersion slope. The tuning range is 70 to 190 ps/nm and 0 to 25 ps/nm2 for the second and third order dispersion, respectively.

Experimental observation of autosoliton propagation in a dispersion-managed system guided by nonlinear optical loop mirrors

Observation of autosoliton propagation in a dispersion-managed optical transmission system controlled by in-line nonlinear fiber loop switches is reported for what is believed to be the first time. The system is based on a strong dispersion map with large amplifier spacing. Operation at transmission rates of 10 and 40 Gbits/s is demonstrated. ©2004 Optical Society of America.