Optical pulse generation and signal processing for the development of high-speed OTDM networks

Due to the continued growth of the Internet and the introduction of new broadband services, it is anticipated that individual channel data rates may exceed lOOGbit/s in the next 5-10 years. In order to operate at such high line rates new techniques for optical pulse generation and optical signal processing will have to be developed. As the overall data rate of an OTDM network is essentially determined by the temporal separation between data channels, an optical pulse source that is capable of producing ultra-short optical pulses at a high repetition rate and with wavelength tunability will be important, not only for OTDM, but for vanous applications in WDM and hybrid WDM/OTDM networks. This work demonstrates that by using the gain-switching technique, commercially available laser diodes can be used in the development of nearly transform-limited optical pulses that are wavelength tunable over nearly 65nm with durations ranging from 12-30ps and a Side-Mode Suppression Ratio (SMSR) exceeding 60dB. New optical signal processing techniques will also have to be developed in order to operate at individual data rates in excess of lOOGbit/s. Only nonlinear optical effects, present in fibres, semiconductors and optical crystals, can be employed as these occur on time scales in the order of a few-femtoseconds (10“15 5), with an example being Two-Photon Absorption (TPA) in semiconductors. This thesis describes a specially designed microcavity that can enhance the Two-Photon Absorption (TPA) response by over three orders of magnitude at specific wavelengths. A theoretical model demonstrating error-free demultiplexing of a 250Gbit/s OTDM signal via a TPA microcavity has been developed. Experimental work is also presented demonstrating the use of a TPA microcavity for optical sampling of 100GHz signals with a temporal resolution of 1 ps9 and system sensitivity of 0 009 (mW)2 This value for the sensitivity is the lowest ever reported for a TPA-based sampling system

Low frequency radio signal polarisation sensor with applications in attitude estimation

This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/ICSENS.2014.6985321A novel system for estimating the attitude (orientation) of a platform using measurements of Low Frequency (LF) radio signals is reported. The sensor system consists of an array of three orthogonal solenoid coil antennas, a three channel radio receiver circuit, a datalogging and control module and data processing algorithms. Traditional low-cost attitude estimation systems typically combine accelerometers, magnetometers and gyroscopes, but produce estimates that are sensitive to platform acceleration. This is a particular problem in high-acceleration, cost-constrained environments such as small fixed-wing Unmanned Aerial Vehicles. The system presented here is shown to accurately measure the axis of polarisation for signals with linear or almost linear polarisation, subject to a sign ambiguity. A representative AM radio broadcast in the LF band is shown to have a substantially linear polarisation, which is used to provide information about the sensor’s attitude and shown to exhibit no drift over a period of 24 hours

Generation of wavelength tunable optical pulses with SMSR exceeding 50 dB by self-seeding a gain-switched source containing two FP lasers

In this letter, we show the generation of shorter pulses (∼20 ps) that exhibit side mode suppression ratios (SMSR's) greater than 50 dB and wider tuning range (48.91 nm). Our technique is based on the self-seeding of a gain-switched source containing two FP lasers

An Exploratory Study of the Role and Contribution of University Knowledge Transfer Offices (KTOs) in Knowledge Transfer and Value Creation

Developed European countries place emphasis on innovation as an important growth driver. Higher educational institutions, within these developed countries, actively participate in regional economic initiatives to proactively transfer and commercialise knowledge to business and society. This knowledge transfer is now performed in a more direct way than heretofore and the commercialization remit is now regarded as the Universities 3rd mission. This is in addition to its traditional remits of education and research. This study explores the effectiveness of the University knowledge transfer process and the contribution that knowledge transfer offices play in knowledge transfer and commercialisation (Value creation). This study uses exploratory in-depth interviews of selected knowledge transfer professionals across the EEA (European Economic Area) to identify the perceived value contributing aspects of the knowledge transfer process and also to evaluate the role and contribution of the Knowledge Transfer office itself in that process.The research finds that: Research institutions in the EEA have between 10 and 25 years in knowledge and technology transfer utilising a systematic approach through a KTO system. The research suggests that the time is appropriate for Universities to recognise knowledge transfer as a ‘mission critical’ activity (3rd mission) in their wider societal remit and that they should therefore prioritise funding for these activities accordingly. Evidence so far suggests that this 3rd mission has yet to achieve’ parity of esteem’ within Universities. The more successful KTOs perform important boundary–spanning roles for the University by marketing the knowledge production skills and abilities in their HEI whilst establishing deep links with indigenous industry and also by attracting multinational clients and projects. This requires the leadership and staff in successful KTOs to possess high levels of cognitive, contextual and organisational ambidexterity. Although difficult, there is also a need to develop appropriate transnational evaluative measures of the output, outcomes and impact for University knowledge transfer processes in the short, medium and long term. Theory–based evaluation utilising a balanced scorecard of evaluative measures (Hard & Soft, Short & Long term) is a methodological approach which can help policymakers and University management to obtain a ‘true and fair’ view of the contribution of the knowledge transfer process to value creation

Simulation of all-optical demultiplexing utilizing two-photon absorption in semiconductor devices for high-speed OTDM networks

The performance of a two-photon absorption (TPA) based demultiplexer in an OTDM communication system is modeled. The demultiplexer is evaluated by comparing the electrical BER of the demultiplexed and detected channel to the optical BER of the signal before the demultiplexer. An error-free demultiplexing of a 250 Gbit/s signal (25 × 10 Gbit/s channels) is shown, using a 30:1 control-to-signal peak power ratio, with a TPA device with a bandwidth of 20 GHz should be possible. The device that is fabricated for TPA is a GaAs/AlAs PIN microcavity photodetector grown on a GaAs substrate

Non-equilibrium defect chemistry in oxygen-rich zinc oxide nano-tetrapods synthesized using atmospheric pressure microplasma †

We demonstrate the synthesis of zinc oxide (ZnO) nanoscale tetrapods (nTP) using an atmospheric pressure microplasma with a metal wire as a sacrificial electrode. ZnO nTPs were characterised using transmission electron microscopy (TEM), X-ray diffraction, ultraviolet-visible and photoluminescence spectroscopy. TEM clearly revealed that the nTP arm length was ∼65 nm and the diameter was around ∼11 nm, grown in the wurtzite phase along the {0001} direction containing polar surfaces. The lattice constants of the ZnO nanocrystals were evaluated using Rietveld refinement. A strong ultraviolet with weak visible-violet emission was observed though photoluminescence revealing that nTP crystals are free from intrinsic defects. Furthermore, the properties of the nTP crystals were compared with those of ZnO nanoparticles formed under different plasma conditions. A detailed formation mechanism based on optical emission spectroscopy and the crystal growth mechanism of the nTP were further discussed

One-step synthesis of strongly confined, defect-free and hydroxy-terminated ZnO quantum dots

This paper reports the production of strongly confined ligand-free, defect-free, hydroxy-terminated ZnO quantum dots with a mean diameter of 1.9 nm, by radio frequency atmospheric pressure microplasma. Systematic characterization is performed to understand the surface chemistry of ZnO quantum dots. Photoluminescence studies show strong confinement effect on emission with only ultraviolet (UV) emission without any defect-related visible emission. Emission is again tested after eighteen months and confirms the QDs long-term emission stability. The mechanism responsible for this UV emission is also discussed and originates from OH-related surface terminations