Generation and optimisation of picosecond optical pulses for use in broadband communication systems

The continued growth of the internet driven by the demand for media rich content and escalating IP traffic has been fuelling the massive growth in demand for bandwidth to handle very high data rates. In order to meet this demand for capacity, optical multiplexing techniques such as wavelength division multiplexing (WDM), optical time division multiplexing (OTDM) and hybrid WDM/OTDM systems need to be utilised. The development of a source of wavelength tunable picosecond optical pulses with excellent temporal and spectral purity at high repetition rates is extremely important for use in such high-speed optical communication systems. The technique of gain switching a commercially available laser diode and self seeding it is shown to be one of the simplest and most cost effective methods of generating transform limited, wavelength tunable pulses with a high Side Mode Suppression Ratio (SMSR). This thesis examines the use of optical gain-switching for the generation of optical pulses that may be used in high-speed OTDM and WDM/OTDM systems. This work specifically deals with the investigation and characterisation of the SMSR and non-linear chirp of optical pulses generated using the gain-switching technique, and outlines how these characteristics, that may degrade system performance, can be optimised such as that optimum performance is attained. In particular, the work demonstrates the development of an optical pulse source with duration 30 dB, jitter 30 dB, that would be suitable for use in OTDM systems operating at 80 Gbit/s

80 Gb/s optimised pulse source using a gain-switched laser diode in conjunction with a nonlinearly chirped grating

The authors demonstrate the generation of transforms limited short optical pulses, which display excellent spectral and temporal qualities by employing a novel technology, based on an externally injected gain-switched laser in conjunction with a non-linearly chirped grating. Using this technique, 3.5 ps optical pulses, exhibiting a time bandwidth product of 0.45, are generated, which are suitable for use in high-speed 80 Gb/s OTDM communications systems

Pulse source for 80 Gb/s systems using a gain-wwitched laser diode followed by a nonlinearly chirped grating

This work presents the generation of 3.5 ps pulses at a repetition rate of 10 GHz and the optimization of the pulse spectrum. The output pulses are near transform limited and have pulse pedestals that are virtually eliminated to 35 dB down from the peak of the pulse, thus providing a source suitable for use in 80 Gb/s OTDM systems

Optimized pulse source employing an externally injected gain-switched laser diode in conjunction with a nonlinearly chirped grating

In this paper, we demonstrate the generation of transform-limited short optical pulses, which display excellent spectral and temporal qualities by employing a novel technology, based on an externally injected gain-switched laser in conjunction with a nonlinearly chirped grating. Using this technique, 3.5-ps optical pulses exhibiting a time-bandwidth product (TBP) of 0.45 are generated, which are suitable for use in high-speed 80 Gb/s optical time-division multiplexing (OTDM) communications systems. The numerical integration of a set of rate equations using suitable parameters for the devices used in the experiments were carried out to further confirm the feasibility of the proposed method for developing an optimized pulse source for high-speed photonic systems

Discrete mode laser diodes with ultra narrow linewidth emission <3kHz

Ex-facet, free-running ultra-low linewidth (<3 kHz), single mode laser emission is demonstrated using low cost, regrowth-free ridge waveguide discrete mode Fabry-Perot laser diode chips

High-power single transverse and polarization mode VCSEL for silicon photonics integration

\ua9 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement. We demonstrate a 6.5 mW single transverse and polarization mode GaAs-based oxide-confined VCSEL at 850 nm. High power is enabled by a relatively large oxide aperture and an epitaxial design for low resistance, low optical loss, and high slope efficiency VCSELs. With the oxide aperture supporting multiple polarization unrestrained transverse modes, single transverse and polarization mode operation is achieved by a transverse and polarization mode filter etched into the surface of the VCSEL. While the VCSEL is specifically designed for light source integration on a silicon photonic integrated circuit, its performance in terms of power, spectral purity, polarization, and beam properties are of great interest for a large range of applications

Discrete mode laser diodes with very narrow linewidth emission

Ex-facet, free-running low linewidth (~100 kHz), single mode laser emission is demonstrated using low cost, regrowth-free ridge waveguide Discrete Mode Fabry Pérot laser diode chips. These narrow linewidths are obtained from sub mW emission powers and above

Butterfly packaged low-linewidth optical comb source

A packaged optical comb source is demonstrated. A low-linewidth optical comb source is designed and fabricated. The device is packaged in a seven-pin high-speed butterfly package with an subminiature version A (SMA) connector for RF modulation and fibre pigtail. Fibre coupling efficiency is estimated at 43%. The packaged comb source is shown to have a linewidth of 300 kHz for the comb line set when modulated at 4 GHz, with eight comb lines within 3 dB of each other. The prototype packaged comb source has applications in high bandwidth telecommunications

Usefulness of quantitative and qualitative angiographic lesion morphology, and clinical characteristics in predicting major adverse cardiac events during and after native coronary balloon angioplasty

Major, adverse cardiac events (death, myocardial infarction, bypass surgery and reintervention) occur in 4 to 7% of all patients undergoing coronary balloon angioplasty. Prospectively collected clinical data, and angiographic quantitative and qualitative lesion morphologic assessment and procedural factors were examined to determine whether the occurrence of these events could be predicted. Of 1,442 patients undergoing balloon angioplasty for native primary coronary disease in 2 European multicenter trials, 69 had major, adverse cardiac procedural or in-hospital complications after ≥1 balloon inflation and were randomly matched with patients who completed an uncomplicated in-hospital course after successful angioplasty. No quantitative angiographic variable was associated with major adverse cardiac events in univariate and multivariate analyses. Univariate analysis showed that major adverse cardiac events were associated with the following preprocedural variables: (1) unstable angina (odds ratio [OR] 3.11; p 45 ° (OR 2.34; p 45 ° (OR 2.87; p 45 ° (OR 2.54; p < 0.006) were independent predictors of major adverse cardiac events