Dispersion decreasing fibres for soliton generation and transmission line loss compensation

The idea of varying the axial distribution of dispersion along a length of optical fibre as a means of manipulating and controlling the soliton supporting nature of the fibre and thereby the characteristics of soliton pulses propagating through the medium has been around for some while. A number of specific applications have been suggested in particular techniques for bright and dark soliton generation, pulse compression and most notably techniques for high frequency soliton transmission. The experimental realisation of most of these techniques however has been hindered by difficulties in the reliable fabrication of dispersion varying fibres. A technique for the fabrication of such fibres was first developed by workers at General Physics Institute, Moscow. Control of the waveguide dispersion was achieved by active control of fibre diameter during the pull. Fibre lengths of up to 2km were fabricated and successfully used in the first experimental demonstrations of high frequency (>60 GHz) bright soliton generation and pulse compression. Subsequent to these first experimental results a number of other groups have commenced fabrication programs on such fibres, extending the techniques to fibre lengths of 40km. In this presentation we describe our latest achievements in Dispersion Decreasing Fibre (DDF) fabrication and report on two applications of the technology. Firstly, we describe a robust, diode-pumped, 40GHz bright soliton transmitter, and secondly we demonstrate loss compensation in a 38km loss-matched dispersion varying fibre

Enhanced photosensitivity in tin-codoped germanosilicate optical fibres

Enhanced photosensitivity is found in Tin-codoped germanosilicate optical fibers. A photo-induced refractive index change (~1.4 x 10-3 times larger than that observed in pure germanosilicate fibers has been demonstrated. Unlike the technique of using Boron-codoping to enhance the photosensitivity of germanosilicate fibers, Tin-doping does not have a significant effect on fiber loss at the important telecommunication window of 1.55µm. High temperature stability of the gratings in Tin-codoped germanosilicate fibers is also much over Boron-codoped fibers

Grating formulation in a phosphorus-doped germanosilicate fibre

Refractive index changes as high as ~5 x 10-4 in a phosphorus-doped germanosilicate fibre were observed for the first time without hydrogen loading during grating formation with a 193 nm laser. Dynamics was studied and it was found that Type IIa gratings was easily formed in this fibre

Photosensitivity in germanosilicate fibres: electronic change or physical change?

Presentation slides<br/

Large photo-induced index changes in tin-doped phosphosilicate fibre

Strong photosensitive gratings of both type I and II have been demonstrated in germanium-free tin-doped phosphosilicate fibre. An index change of ~1.2 x 10-3 has been achieved in 40 seconds of exposure. This is the first time that such strong gratings were written in a phosphorous-containing silica fibre and that type II gratings were written in a germanium-free fibre

Dark soliton generation and propagation using a normally dispersive, dispersion decreasing fiber

The generation and propagation of bright and dark soliton pulses is an area of great scientific interest with relevance to many futuristic telecommunication and optical-processing applications. Bright solitons have been the subject of intense experimental investigation; however, the experimental study of dark soliton behaviour has been limited. This situation is in no small part due to the difficulty of generating and measuring such pulse forms [1,2,3]. (for review see Ref.[4] and references within)

Transmission and modulation of 30-40 GHz pulses generated by a diode-driven, low-jitter, beat-signal to soliton train conversion source

We report on the performance of a low timing-jitter, diode-driven, Nd:YLF pumped 5ps, 30-40 GHz soliton source based on beat signal conversion in a dispersion decreasing fibre. We demonstrate for the first time data encoding at 40 Gbit/s and transmission of the pulse trains over 205 km

High-frequency bright and dark soliton sources based on dispersion-profiled fibre circuitry and their applications

We report advances in the area of soliton generation using beat signal conversion. In particular, we describe the development of a diode-driven, 40 GHz bright soliton source with sub 300 fs pulse jitter. Furthermore we report pulse transmission and all-optical data encoding at 40 Gbit/s

Malignant pleural effusion: updates in diagnosis, management and current challenges

Malignant pleural effusion (MPE) is a common condition which often causes significant symptoms to patients and costs to healthcare systems. Over the past decade, the management of MPE has progressed enormously with large scale, randomised trials answering key questions regarding optimal diagnostic strategies and effective management strategies. Despite a number of management options, including talc pleurodesis, indwelling pleural catheters and combinations of the two, treatment for MPE remains symptom directed and centered around drainage strategy. The future goals for providing improved care for patients lies in changing the treatment paradigm from a generic pathway to personalised care, based on probability of malignancy type and survival. This article reviews the current evidence base, new discoveries and future directions in the diagnosis and management of MPE

Chirped fibre Bragg gratings fabricated using etched tapers

We have demonstrated a technique which is capable of controllably producing fibre Bragg gratings with arbitrary chirp profiles using etched tapers. Gratings with 4.8nm linear chirp have been produced. Nonlinearly chirped gratings have also been demonstrated