Thesis (Ph. D.)--School of Electrical and Computer Engineering, Georgia Institute of Technology, 2004. Directed by Nan M. Jokerst. / Vita. Includes bibliographical references (leaves 132-140).

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 98-103).

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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Narrowband optical filtering and chromatic dispersion are two important issues that affect optical fiber transmission performance. Recent technological developments in high-speed digital signal processors, digital-to-analog converters and analog-to-digital converters have enabled the implementation of electronic signal processing (ESP) in optical transmission systems leading to adaptive and cost efficient integrated solutions. This thesis focuses on applying ESP at the transmitter to pre-compensate for narrowband optical filtering and chromatic dispersion. A novel electronic pre-compensation approach was proposed to deal with narrowband optical filtering. The effectiveness was demonstrated by a straight-line experiment and a recirculating loop experiment for 10 Gb/s non-return-to-zero on-off-keying (NRZ-OOK). Moreover, the work was extended to NRZ differential-phase-shift-keying as well as 20 Gb/s NRZ differential-quadrature-phase-shift-keying. Experimental results demonstrate that electronic pre-compensation effectively reduces the degradation in system performance induced by narrowband optical filtering. Electronic dispersion pre-compensation was investigated using a semiconductor InP Mach-Zehnder modulator (MZM) for the NRZ-OOK modulation format at 10.709 Gb/s aiming at providing a cost efficient implementation for core and metro transmission networks. A brute-force method was developed to determine the requisite drive i voltages due to the nonlinear voltage dependent attenuation and phase constants of the InP MZM. The transmission results for the recirculating loop and straightline experiments demonstrate that an InP MZM provides comparable dispersion precompensation performance with a conventional LiNbO3 MZM. Use of the NRZ-OOK modulation format and InP MZM provides a simple and cost-efficient solution for core and metro transmission network. Dispersion pre-compensation was also performed for a 85.672 Gb/s polarization multiplexed 16-ary quadrature amplitude modulation (PM-16QAM) modulation format with digital coherent detection and offline digital signal processing. The transmitter was characterized to ensure the quality of the 16QAM signal generation. Simulation results indicate the impact of the modulator bias voltage error on system performance. Recirculating loop experimental results demonstrate that the performance of dispersion pre-compensation is comparable with dispersion post-compensation, thus providing the possibility to combine dispersion pre- and post-compensation for PM- 16QAM coherent transmission for further performance improvement. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2011-10-29 13:01:01.347

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