Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 118-130).

Includes bibliographical references (p. 137-147).

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Zhou, G. Tong; Committee Member: Johnson, Ellis; Committee Member: Kenney, J. Stevenson; Committee Member: Li, Ye; Committee Member: Ma, Xiaoli. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Multimode fibers (MMF) are generally used in short and medium haul optical networks owing to the availability of low cost devices and inexpensive packaging solutions. However, the performance of conventional multimode fibers is limited primarily by the presence of high modal dispersion owing to large core diameters. While electronic dispersion compensation methods improve the bandwidth-distance product of MMFs, they do not utilize the fundamental diversity present in the different modes of the multimode fiber. This thesis draws from developments in wireless communication theory and signal processing to motivate the use of multiple-input multiple-output (MIMO) and signal processing techniques in MMF links. MIMO techniques that utilize the diversity of modes present in the fiber increase data rates and link reliability. Theoretical models for propagation effects in MMF systems are used to analyze and design the geometry of laser and detector arrays for MIMO-MMF links, and study how the design of these arrays impacts link performance. These models are also used to develop and evaluate low-complexity algorithms that efficiently utilize dense detector arrays, with "greedy subset selection" based on submodular optimization. Experimental evaluation of 1 × 1, 2 × 2, 3 × 3 and 4 × 4 MIMO systems have been conducted over various MMF media, including 100 m - 3 km silica MMF with externally modulated distributed feedback lasers and directly modulated vertical cavity surface emitting lasers (VCSELs), as well as with Fabry Perot lasers over 10 m - 100 m plastic MMF. The use of off-the-shelf components as well as the role of axial offset coupling in enhancing modal diversity has been experimentally quantified. The experimental techniques discussed in this thesis have enabled an increase of over 25× in the bandwidth-distance product of the MMF link, when compared to currently deployed MMF systems, such as 10GBASE-SR. / text

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Optical networks with Wavelength Division Multiplexing (WDM) technology provide huge bandwidth to meet the ever-increasing traffic demand of the next generation Internet. But the high-speed nature of WDM networks also makes the network more vulnerable to failures. Even a single network failure for a very short duration can result in enormous loss of data. In this thesis, we concentrate on designing a survivable WDM network. In essence, survivability concerns two important aspects, fast fault detection and localization, and fast fault recovery. We first study fast fault detection and localization in WDM optical networks. Our work is based on the notion of monitoring cycle (m-cycle). Compared with other fault detection schemes, an m-cycle based fault detection scheme provides fast fault detection and requires less number of expensive monitors. Aiming at further cutting down the implementation cost, we propose the notion of super monitor. Instead of having a dedicated monitor for each m-cycle, a single super monitor can be placed at the junction of a set of overlapped m-cycles. In this thesis, we formulate and solve the monitor placement problem. We then focus on enhancing the capacity efficiency of fast fault recovery schemes. Shared backup path protection (SBPP) schemes can provide 100% protection against any single link failure. This is achieved by establishing a pair of link-disjoint active and backup paths upon each call arrival. The bandwidth on different backup paths can be shared for protecting different calls. In this thesis, a new SBPP scheme is designed based on a two-step routing approach, where the active and backup paths are sequentially optimized with different objectives in mind. We then shift our focus to design fast protection scheme for multicast/broadcast communications. To this end, we refine the existing concept of blue/red tree. Blue/red tree is a pair of spanning trees where the connectivity between the root and any destination node is ensured upon a network failure. In particular, two efficient integer linear programs (ILPs) are formulated for finding the optimal blue/red trees. Last but not the least, we investigate the survivability in IP networks. We notice that existing efforts on IP fast reroute (IPFRR) are effective in enhancing the IP resilience. But the impact of IPFRR on the end-to-end TCP performance is ignored. Notably, path rerouting can interfere with the TCP congestion control mechanism and thus cause severe throughput degradation. To address this problem, we propose a duplicate acknowledgement (ACK) suppression scheme. The key idea is to detect whether an out-of-order packet arrival event is due to IPFRR or not. If it is due to IPFRR, duplicate ACKs triggered will be suppressed by the TCP receiver so as not to cause unnecessary slow down at the TCP sender. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

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