Performance of photonic oversampled analog-to-digital converters.
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Date
2007
Authors
Clare, Bradley
Editors
Advisors
Corbett, Kerry Anne
Munch, Jesper
Munch, Jesper
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Thesis
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Abstract
In an increasingly digital world, the need for high speed and high fidelity analog-to-digital (A/D) converters is paramount. Performance improvements in electronic A/Ds have not kept pace with demand, hence the need to consider alternative technologies.
One such technology is photonics, as it takes advantage of optical sampling, high speed optical switches and low cross-talk interconnects. Optical sampling derives its advantage from the application of ultra low timing jitter (<100fs) mode locked lasers utilised to provide high speed clock pulses.
In this thesis the feasibility and simulated performance of three different types of photonic oversampled A/D converters was investigated. The first, and simplest design is that of oversampled pulse-code-modulation (PCM), where a 2-level photonic comparator is used to sample the analog input at a frequency much greater than the Nyquist frequency. Subsequent low pass filtering produces a digital representation of the input. The other two architectures that were investigated are the first-order sigma-delta and error diffusion, which add one
level of error correction to the PCM technique. These two architectures require the functional elements of a subtractor, comparator and delay. The photonic comparator and subtractor functionality was provided by Self-Electro-Optic Effect devices
(SEED) based upon multiple quantum well (MQW) p-i-n devices.
To facilitate calculation of the performance of the different architectures and aid in device design, a simulation of SEED operation based upon experimental data was developed. The simulation’s accuracy was demonstrated by agreement with the
results from experimental S-SEED switching and optical subtraction. To emphasize the utility of the model, the simulation was subsequently used to demonstrate tristability of an S-SEED and critical slowing down in a bistable S-SEED. These
effects were experimentally verified.
To provide enhanced comparator contrast ratio and subtractor dynamic range, resonantly enhanced microcavity multiple quantum well (MQW) p-i-n devices were designed and grown by MOCVD. The operation of the subtractor and comparator was experimentally demonstrated and utilising temperature tuning, optimised performance was achieved with devices from the same wafer. Furthermore, the inclusion of gain was shown to improve the subtractor performance to that demanded by the sigma-delta.
The constraints on each architecture imposed by the unipolar nature of the light intensity were derived and the sigma delta architecture was shown to be superior to the error diffusion for a photonic implementation. Using the numerical simulation based upon experimentally derived data, the entire sigma delta architecture was simulated to calculate the expected performance. The signal-to-quantisation-noise ratio (SQNR) was calculated as a function input amplitude and a peak SQNR of 54dB was obtained for an oversampling ratio of 100.
School/Discipline
School of Chemistry and Physics : Physics and Mathematical Physics
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2007
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Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.
This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exception. If you are the author of this thesis and do not wish it to be made publicly available or If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals
This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exception. If you are the author of this thesis and do not wish it to be made publicly available or If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals