Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 141-153). Available also in a digital version from Dissertation Abstracts.

Undergraduate honors paper--Mount Holyoke College, 2005. Dept. of Physics. / Includes bibliographical references (leaves 73-74).

Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on Feb. 24, 2009). Includes bibliographical references.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007. / Bennett, Gisele, Committee Member ; Rhodes, William, Committee Member ; McLaughlin, Steven, Committee Member ; Barry, John, Committee Co-Chair ; Chang, Gee-Kung, Committee Chair ; Chapman, Michael, Committee Member.

M.Ing. (Electrical and Electronic Engineering) / During the past decade the optical disc has become increasingly popular. Write-once optical recording systems will mainly be used in data storage systems in which archival aspects or mass storage requirements prevail. In write-once optical data storage one is faced with an asymmetry between marks and non-marks due to a practical lower limit of the mark size. In some optical fibre communications there is also an asymmetry present in injection lasers and it may be feasible to use asymmetrical codes. In this study information theoretical methods are used to find values of channel capacity for sequences complying with binary asymmetrical runlength constraints. Different coding methods are used to construct encoders and decoders for generating and decoding these sequences with high values of efficiency. The power spectra of maxentropic binary asymmetrical runlength limited sequences complying with different runlength constraints are also investigated.

M.Ing. / All-optical networks, although highly promising, have a long way to go before they will replace existing optical networks such as SONET. The development of the all-optical networks relies on the components market to supply reliable and integrated components to facilitate filtering and management in the optical domain. Planar lightwave circuits (PLCs) and photonic integrated circuits (PICs) provide the answer, with the potential of integrating various functions on a single substrate. The design of lightwave circuits starts with the design and testing of a waveguide. Once this manufactured waveguide exhibits the right characteristics and is proved to be reproducible, it can be used in the design of components. In industry, this design is done by utilizing the beam propagation method (BPM). In order to design useful circuits, the simulation results of simple structures should be compared with experimental results to check their sensitivity to certain parameters. Once the relationship between manufactured and simulated components is understood, the design of components can commence with confidence. In this thesis, BPM simulation results are compared with a reported manufactured waveguide, and then used to design various components used for filtering purposes in dense wavelength division multiplexed (DWDM) systems. Designs for the couplers that serve as building blocks for the filters are discussed, and a novel technique of design downscaling is presented for bi-directional couplers. The filters under investigation are all moving average filters, namely Mach-Zehnder lattice filters, and the highly integrated arrayed waveguide gratings (AWGs). Applications for both these filters are presented.

Please read the abstract in the section 00front of this document / Dissertation (MSc (Applied Science))--University of Pretoria, 2006. / Electrical, Electronic and Computer Engineering / unrestricted

The topic of this thesis is aerial optical fibres in telecommunication systems: state of polarization (SOP) and polarization mode dispersion (PMD) monitoring and tolerance of modulation formats. Errors in optical fibre telecommunication systems are introduced when these polarization effects (SOP and PMD) change. These changes are so intense especially in aerial optical fibres. Part of the backbone of South Africa’s national grid includes long distances of aerial optical fibre between transmission exchange stations. The work in this thesis can be divided into three parts which all deal with the major aspects of PMD in deployed aerial optical fibres: characterization, environmental effects plus other perturbations, and tolerance of different modulation formats. In our work, SOP and PMD field measurements revealed that they both fluctuate more rapidly in deployed aerial optical fibres especially on windy and hot days. The SOP and PMD changes in the aerial optical fibres showed a significant correlation with these environmental parameters. SOP and PMD are stochastic in nature due to changes in the properties of the optical fibres and its positions because of both intrinsic and extrinsic perturbations. In our work, with only 184 PMD values measured and obtained by use of the FTB-5700 single-ended dispersion analyzer, the predicted theoretical Gaussian fit was obtained with a mean of 0.47 ps and standard deviation of 0.08 ps. This small standard deviation was justification for its robustness and accuracy. The statistical distributions for first-order polarization mode dispersion (FO-PMD) and second-order polarization mode dispersion (SO-PMD) for the first time were experimentally confirmed when measured using the FTB-5700 single-ended dispersion analyzer instrument for deployed aerial optical fibres. We were also able to determine the time scale over which to compensate FO-PMD in deployed aerial fibres using the directional time drift autocorrelation function method. It is slightly higher than 390 s for SOP measurements made on a particular windy and hot day. This is due to the fact that the changes of the PMD vector are known to be slower than the SOP changes. vi We also investigated the theoretical statistical distribution that corresponds to output SOP variations. The SOP variations can either be with wavelength (for buried fibre) or with time (for aerial fibre). Our results showed that the statistics of the relative SOP changes approached the distribution proposed by Foschini et al. (2000). Advanced optical modulation formats have become a key ingredient in the design of modern state-of-the-art wavelength-division-multiplexed (WDM) optical transmission systems. In our work, we investigated which of these advanced modulation formats is best suited for the South African network especially on systems that have links of aerial optical fibres. Keywords: aerial optical fibre, polarization mode dispersion (PMD), principal states of polarization (PSP), state of polarization (SOP), first-order PMD, second-order PMD.

A prototype communication system has been designed, built and tested. The system is a digital communication system that uses near infrared radiation transmitted through the atmosphere. The prototype system consists of two transceivers, each with associated electronics and power supplies. Each transceiver is capable of simultaneously transmitting and receiving light at a wavelength of 830 nm . The transmitter emits light in a 0.3 degree (full angle) cone through the atmosphere , while the receiver accepts light within its 0.33 degree field of view. For the purpose of alignment, each receiver also has an eyepiece and alignment reticle with a field-of-view of approximately 1.5 degrees. The system is capable of transmitting and receiving digital data at a rate of up to 72 thousand bits per second (kbps) over a distance of 0 . 2 km on a clear day with an average transmitted power of less than 100 MW. Data is encoded for transmission using Pulse Position Modulation (PPM). The transmitting electronics include a pulse code modulation (PCM) voice digitizer, PPM modulator, and infrared emitter driver circuitry. The receiving circuitry includes a photodiode with bias supply and preamplifier, PPM automatic gain control, PPM demodulator, and PCM digital to analog converter Finally, a model has been developed which describes system performance. The model may be used for investigating the performance of other similar systems which may need t o meet specific design criteria or restrictions.

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