High quality 5ps pulse generation at 10 Gbit/s using a fibre Bragg grating compensated gain-switched laser diode

A fibre Bragg grating is designed to spectrally filter and perfectly compensate the chirped pulses from a gain-switched laser diode. This design is based on the exact characterisation of the intensity and phase profiles using an electro-optic pulse characterisation technique. This results in a compact pulse source that should produce high quality 5 ps duration pulses with a 50 dB pedestal suppression

Detailed comparison of injection-seeded and self-seeded performance of a 1060nm gain-switched Fabry-Perot laser diode

We investigate and compare the performance of a gain-switched picosecond Fabry-Perot laser diode operated at 1.06 µm under both injection- and self-seeded conditions. Our experiments show that comparable performance can be obtained for both modes of operation, with the self-seeding arrangement offering overall benefits in terms of reduced system complexity and cost, providing the associated quantization of available pulse repetition rate can be tolerated

Editorial

We use a linear FROG technique based on electro-optic modulation to fully characterise for the first time pulses from a 1.06 µm FP laser diode and design a grating to provide optimum pulse compression

Advances in high power short pulse fiber laser systems and technology

We review recent advances in Yb fiber lasers and amplifiers for high power short pulse systems. We go on to describe associated recent developments in fiber components for use in such systems. Examples include microstructured optical fibers for pulse compression and supercontinuum generation, and advanced fiber grating technology for chirped-pulse amplifier systems

Multi-wavelength EAM based optical sampling for performance monitoring in high bit-rate systems

The intensity and phase profiles of eight 10 Gbit/s WDM channels on a 200 GHz grid have been simultaneously measured using a spectrally resolved optical gating technique, based on sampling with a single electro-absorption modulator

Precise intensity and phase characterisation of optical telecommunication signals

In this thesis, the accurate characterisation of a range of high speed optical telecommunication signals is presented. The main technique used to determine both the intensity and the phase profiles of these signals is based on spectrograms, and various developments and extensions of this method are presented. Finally, data modulated pulses in a 40 Gbit/s system are characterised before and after propagation in an installed fibre link, and excellent agreement is found between the information retrieved from the spectrogram method, independent intensity measurements and theoretical expectations

A novel XPM based pulse retiming system incorporating a fibre grating based parabolic pulse shaper

A novel all-optical, all-fibre pulse retiming system is experimentally demonstrated. Our technique relies on converting the timing jitter into frequency shift using XPM switching of the data signal with parabolic pulses shaped using a SSFBG

Direct characterization of the spatial effective refractive index profile in Bragg gratings

We propose a pulse response method to directly characterize the phase of the spatial index modulation, including the dc refractive index distribution (distributed phase shift), discrete phase, and chirp of fiber Bragg gratings (FBGs). This method is based on the observation that the spatial phase of gratings is directly related to the temporal phase of its pulse response. Therefore, the phase of the spatial index modulation can be characterized directly by measuring the temporal phase of the pulse response of FBGs. This method is then used to characterize an FBG with a current-induced phase shift

Possible future applications of photonic bandgap fiber in non-repeatered transmission systems

We investigate the potential use of photonic bandgap fibers in non repeatered transmission systems. Our simulations show that significant improvements in system reach should be possible as a result of the reduced nonlinearity providing that the fiber losses can be reduced to the 0.2 to 0.3dB/km regime

Irritable bowel syndrome is the commonest cause of abdominal pain in childhood

Apley, working in Bristol, UK, defined recurrent abdominal pain (RAP) in 1958. After extensive investigations, he found that 8% of children presenting to his clinic with RAP had an organic pathology. The aims of this study were to identify (1) causes of RAP using modern methodology, (2) factors associated with organic RAP and (3) children with none-organic RAP who fulfill the diagnostic criteria for irritable bowel syndrome (IBS). Children, aged over 3 years, presenting with RAP were prospectively recruited to this study. They had a detailed questionnaire completed, a full examination with screening tests (blood for coeliac screen, Helicobacter pylori antibody titre, inflammatory markers, serum amylase, liver function tests, and full blood count, urine and stool analyses and abdominal ultrasonography). Endoscopy and oesophageal pH monitoring were performed if clinically indicated. IBS was diagnosed if the child had no organic pathology and fulfilled the Rome II criteria. Out of 103 children (median age of 10 years, mean 10.04, SD ± 3.44,), 31 children (30%) had organic pathologies. Factors associated with organic pain were nocturnal symptoms (P < 0.01) and abdominal tenderness (P < 0.005) and with non-organic pain were periumbilical locality (P < 0.002), pain alleviation on defaecation (P < 0.04) and low fibre diet (P < 0.005). Of children with non-organic pain, 37/52 (51%) fulfilled the criteria for IBS (36% of the total). Conclusion: Of children presenting with recurrent abdominal pain in a hospital setting, 30% have a diagnosable organic aetiology compared to 8% in Apley's time. Irritable bowel syndrome, however, may be the commonest cause of recurrent abdominal pain and should be considered