這篇論文討論了三個重要的全光網絡的網絡管理方向，分別為在全光封包交換網絡的光路追踪問題，光封包的暫存及在波分複用無源光網絡（WDM-PON）的能源節省運作。 / 使用全光編碼器進行光路追踪 / 在所有全光封包交換網絡中，數據包的路由光路是可以被通過光學交叉連接（OXC）的網絡節點重新配置。要監控任何可能的路由錯誤、信號質量下降的任何可能的原因、發現任何惡意或攻擊流量的來源、或提供服務質量（QoS）的路由策略，光學數據包的光路監測是必要的。此方案編碼光路信息到光學數據的標籤，每個網絡節點被分配一個獨特的質數為識別標記的光路信息。使用位於OXC輸出端的光學編碼器，每次當數據包通過該網絡節點時，數據包的標籤值將乘以特定的質數。網絡數據包已經走過的節點將被編碼的標籤為代表的網絡節點的所有素數的乘積。因此，在標籤的檢示器中，光數據包走過的每個網絡節點都可以很容易地通過標籤值的因式分解求得。 / 相比使用時間延遲識別技術，我們的設計大幅減少了光纖線的長度要求。此外，與導頻訊號檢測方法相比，它提供了快速檢測的好處。此外，網絡循環的問題也可以檢測。編碼標籤也可以作為的光封包的保存週期指示器（TTL）。 / 功率控制的全光封包緩衝器 / 全光封包緩衝區全光交換網絡中是非常重要的。為了實現簡單而有效的光學數據包緩衝操作，我們提出使用功率控制時間延遲的全光數據包緩衝區。的循環迴路的數量是由輸入信號的功率控制（即具有較高的功率輸入信號將經歷更長的時間延遲）。我們把偱環延遲緩衝器重新設計成信號功率依賴過濾的問題。光信號首先通過在不同的時刻，每延遲副本將減半功率與前一個通過循環生成多個副本的循環。然後，它會通過信號的功率大子而使用非線性光學效應來實施過濾。過濾器只與特定功率水平的信號，可以輸出，而別人得到減毒，因此清除的特點。因此，為了改變延遲量，我們只需要改變輸入信號功率等具體延遲的信號，將陷入電源依賴的濾波器的通帶和輸出。 / 比起使用許多的SOA來控制循環延遲或使用可調諧波長轉換器及波長依賴時滯的方案，我們的計劃提供更容易的延遲控制。 / 信號電源效率的WDM-PON的操作技巧 / 在WDM-PON中，光網絡單元（ONU）的上傳信號通過對由光線路終端（OLT）的下傳信號的重新編寫產生。傳統上，這設計產生功耗的問題。例如：如果沒有下傳信號，光網絡單元不能發送上傳數據。因此，即使沒有數據傳送，光線路終端也要不斷傳送下傳信號，為了確保光網絡單元總是能夠發送上傳數據。在這種網絡中，突發傳送模式可以提供電源效率上的節省。我們提出了一個信號傳送技術來由光網絡單元向光線路終端發送“喚醒消息，以通知光線路終端的收發器從睡眠模式恢復。這技術是通過對在RSOA放大自發輻射（ASE）噪聲進行特定導頻信號的，因而不需要重新調制下游信號。在光線路終端，額外的模塊將負責檢測不同光網絡單元的導頻信號，然後啟動相應的收發器。我們的計劃提供了在WDM-PON的簡單和高成本效益的能源節省方案。 / This thesis addresses three important network management aspects of optical networks, namely, optical lightpath tracing problem for all-optical networks, all-optical packet buffering in optical packet switching networks, power-efficient operation in wavelength division multiplexing passive optical networks (WDM-PON). / Lightpath tracing through all-optical encoder / In an all-optical reconfigurable wavelength routing network, the lightpath of the optical data packets can be reconfigured, via the optical cross connects (OXC) residing at each network node. In order to monitor any possible routing errors, any possible causes of signal quality degradation, detect any source of malicious or attack traffic and provide quality of service (QoS) aware next-hop routing strategy, monitoring of lightpath of optical data packets is necessary. This scheme encodes the lightpath information into the label of individual optical packet. Each network node is assigned with a distinct prime number as an identification tag. By using the optical encoders located at the outputs of OXCs, the label value of the packets will be multiplied by the prime number designated to the respective OXC, residing at the network node. Hence, the information of the network nodes that the packet has traversed will be encoded to the label as the product of all the prime numbers assigned to all traversed network nodes. Therefore, at the destination node, the whole physical lightpath of each received optical data packet can be easily identified through factorization of the encoded label value. / Our scheme provides substantial reduction in the requirement of fiber delay lines, as compared to the time-delay recognition techniques. It offers fast detection when comparing with pilot tone detection method. Besides, possible network looping problem can be detected and the encoded label can be acted as time-to-live (TTL) identifier of the optical packet. / All-optical power-controlled optical packet buffer / All-optical packet buffer is essential for the contention resolution in all-optical packet switching network. In order to realize simple and efficient operation of optical packet buffer, we propose the use of all-optical power-controlled packet buffer for which the number of circulating loops is controlled by the input signal power (i.e. input signal with higher power will experience longer delay). We formulate the problem of designing a re-circulating delay buffer into signal power dependent filtering problem. The optical OOK signal first passes through a re-circulating loop generating multiple copies at different time instants that each delayed copy will have halved power as the previous one. Then it will pass through the signal power dependent filter implemented by using optical nonlinear effect. The filter has the characteristics that only signal (packet copy) with specific power level can be outputted while the others get attenuated and therefore cleared. As a result, in order to change the amount of delay, we just need to change the input signal power such that the signal with specific delay will fall into the pass band of the power dependent filter and get outputted. / Compared with other delay schemes which use many SOAs as gates to control the number of re-circulating delay or implementing tunable wavelength converter and passes through wavelength dependent delay, our scheme provides easy control of the delay required. / Signaling techniques for power-efficient operation of WDM-PON / In WDM-PON, the upstream signal at the optical network unit (ONU) can be generated by re-modulating the downstream signal received from the optical line terminal (OLT). However, the conventional architecture may suffer from power consumption problem. When there is no downstream signal, the ONU is not able to send any upstream data. Thus even if there is no traffic on the line, the OLT has to send the downstream signal continuously, in order to ensure the ONU can always be able to send its upstream data. In such networks, burst-mode traffic transmission can provide improvement on power efficiency. We propose a signaling technique to send “Wake Up message from the ONU to OLT, to notify the transceiver of the OLT to recover from sleep mode. It is done by modulating the Amplified Spontaneous Emission (ASE) noise in RSOA at the ONU with the particular ONU specific pilot tone monitoring signal. Thus, it does not require the presence of the remodulating downstream signal. At the OLT, a specific module is needed for the detection of the pilot tones from different ONUs and then activate the corresponding transceiver. Our scheme offers simple and cost-effective approach for power-efficient operation in the WDM-PON. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Tse, Kam Hon. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 90-97). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract --- p.i / Acknowledgements --- p.viii / Chapter Chapter 1 --- Background --- p.1 / Chapter 1.1 --- All-Optical Packet Switching Networks --- p.3 / Chapter 1.1.1 --- Packet Buffering --- p.4 / Chapter 1.1.2 --- Route Tracing --- p.7 / Chapter 1.2 --- Wavelength Division Multiplexing Passive Optical Networks (WDM-PON) --- p.12 / Chapter 1.2.1 --- ONU Upstream Re-Modulation in WDM-PON --- p.12 / Chapter 1.2.2 --- Green Networking --- p.13 / Chapter 1.3 --- Contributions --- p.17 / Chapter 1.3.1 --- Path Tracing Scheme for All-Optical Packet-Switched Networks --- p.17 / Chapter 1.3.2 --- All-Optical Power-Controlled Optical Packet Buffer for All-Optical Packet-Switched Networks --- p.18 / Chapter 1.3.3 --- Signaling Techniques for Power-Efficient Operation of WDM-PON --- p.19 / Chapter 1.4 --- Organization of Thesis --- p.19 / Chapter Chapter 2 --- Path Tracing Scheme for All-Optical Packet-Switched Networks --- p.21 / Chapter 2.1 --- Introduction --- p.21 / Chapter 2.2 --- Path Tracing Using Prime-Number Tags --- p.26 / Chapter 2.2.1 --- Network Node Tracing --- p.26 / Chapter 2.2.2 --- Network Link Tracing --- p.28 / Chapter 2.2.3 --- Network Looping Problem --- p.29 / Chapter 2.3 --- Optical Implementation --- p.30 / Chapter 2.4 --- Experimental Results --- p.38 / Chapter 2.5 --- Multi-Level Amplitudes Of The Label --- p.41 / Chapter 2.6 --- Required Maximum Fiber Delay --- p.44 / Chapter 2.7 --- Summary --- p.47 / Chapter Chapter 3 --- A Novel Fiber-based Variable All-Optical Packet Buffer based on Self-Phase Modulation Induced Spectral Broadening --- p.48 / Chapter 3.1 --- Introduction --- p.48 / Chapter 3.2 --- Input signal power dependent delay --- p.51 / Chapter 3.3 --- Numerical Simulation Studies --- p.54 / Chapter 3.4 --- Experimental Results --- p.64 / Chapter 3.5 --- Discussion --- p.68 / Chapter 3.6 --- Summary --- p.71 / Chapter Chapter 4 --- A Cost-effective Pilot-Tone-based Monitoring Technique for Power Saving in RSOA-based WDM-PON --- p.73 / Chapter 4.1 --- Introduction --- p.73 / Chapter 4.2 --- Proposed System Architecture --- p.75 / Chapter 4.3 --- Experimental Setup and Result --- p.78 / Chapter 4.4 --- Power Saving Efficiency Calculation --- p.82 / Chapter 4.5 --- Summary --- p.86 / Chapter Chapter 5 --- Conclusions and Future Work --- p.87 / Chapter 5.1 --- Conclusions --- p.87 / Chapter 5.2 --- Future Work --- p.88 / Bibliography --- p.90 / Publications during PhD Study --- p.98

本文提出一种新颖的动态全光网络监控分布式算法，该算法可估计光网络中光纤链路上的误码率，在不需要额外光监控元件的情况下同时监控，检测和定位多处光纤链路损坏。 / 在光网络传输过程中，各个终端结点的接受机可以时时地估计出收到光流的误码率，这些误码率信息可以通过扩展OSPF-TE协议在全网共享。基于这些共享的误码率信息，我们将光纤损坏检测问题抽像成一个线性编程（LP）算法，其中每一个误码率信息代表一个限制条件。我们之后运用一些算法优化技巧将这个问题的维度和复杂度大大地降低，以便可以直接嵌入到每个网络结点可能自带的微处理器单元中进行实时计算运用。本文提出的算法同时适用于没有光波长转换器的光网络和配备光波长转换器的光网络。 通过沿用OSPF协议的分层多域思想，大规模网络可以分化成小的域和连接各域的主干网络，从而可以将一个复杂的大规模网络检错问题转化成一系列简单小网络检错问题。通过将该算法在一个由408 节点组成，支持40波长的大规模GMPLS 网络仿真平台上仿真，算法的有效性得到了验证。 / 为了保证用于仿真的网络流量模型合理且符合实际，本文也对动态全光网络流量模型做了一定研究。在自相似网络流量模型下，我们发现长短光流的不公平性问题可以给动态全光网络带来很大问题，会大大地降低网络的吞吐率。我们运用一种截短长光流的方法可以将这个问题很有效地解决。 / 据我们所知，这是目前唯一的一个能运用于现实中超大规模光网络的低成本可实现且可以作到波长级监控和同时监控多个链路错误的算法。该方法可以不用额外添加昂贵的光监控元件就可实现对动态全光网络的监控，并且该方法同时适用于透明，半透明及配置波长转换器的光网络。 / A new and efficient distributed algorithm for estimating the bit-error-rate (BER) of links in dynamic optical networks is proposed. The method can be used to monitor, detect and localize multiple soft link-failures without incurring any additional optical monitoring equipment. During the transmission of each optical flow the end node’s receiver can estimate the digital BER information, and the BER information can be shared among the network by extending the Open Shortest Path First-Traffic Engineering Extension (OSPF-TE) protocol easily. We model the faults localization problem as a linear programming (LP) algorithm, where each BER information measured from a flow serves as a constraint. Optimization techniques are applied to significantly simplify the complexity of the LP algorithm in order to make it solvable in real time by an integrated processor attached to the network node. The proposed algorithm is capable of monitoring networks with or without wavelength converters. A large scale network can be divided into several layers according to the OSPF protocol, thus the algorithm can be applied to large networks in the real world similar to OSPF. The monitoring algorithm is demonstrated by network simulations over a 408-node, 40-wavelength network test-bed where up to twenty faulty links are identified. / To make sure the traffic generator model is reasonable, the traffic model for dynamic all-optical network is also studied in this work. Under self-similar traffic, we found that the dynamic optical networks suffer from the long flow short flow unfairness problem, which would reduce the throughput as well. So a segmentation strategy is proposed to solve this problem. / To the best of our knowledge, this is the first realistic and low-cost framework which can monitor channel level BER changes to identify multi-link-failures efficiently for large scale dynamic all-optical WDM networks, without using expensive optical monitors or additional supervisory channels. The approach proposed is applicable to transparent, translucent and wavelength-converted optical networks. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Li, Huadong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 64-66). / Abstracts also in Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Backgrounds --- p.11 / Chapter 2.1 --- ROADMs, Dynamic networks --- p.11 / Chapter 2.1 --- Types of failures considered: --- p.13 / Chapter 2.2 --- Brief review of OSPF routing protocol --- p.15 / Chapter Chapter 3 --- Traffic model used --- p.16 / Chapter 3.1 --- Introduction --- p.16 / Chapter 3.2 --- LFSF unfairness problem --- p.19 / Chapter 3.3 --- Flow segmentation strategy --- p.23 / Chapter 3.4 --- Simulation results --- p.24 / Chapter 3.5 --- Summary and Conclusion --- p.29 / Chapter Chapter 4 --- Estimated digital BER monitoring and faults diagnosis algorithm --- p.31 / Chapter 4.1 --- Intra-domain faults diagnosis algorithm --- p.31 / Chapter 4.2 --- Hierarchically layering scheme for inter-domain network monitoring --- p.37 / Chapter Chapter 5 --- Simulation results and analysis --- p.40 / Chapter 5.1 --- Simulation set up --- p.40 / Chapter 5.1.1 --- 100Gbps simulation set up --- p.40 / Chapter 5.1.2 --- 10Gbps simulation set up --- p.42 / Chapter 5.2 --- Simulation results --- p.44 / Chapter 5.2.1 --- 100Gbps simulation results: --- p.44 / Chapter 5.2.2 --- 10Gbps simulation: --- p.51 / Chapter 5.3 --- Conclusion --- p.61 / Chapter Chapter 6 --- Conclusion --- p.62 / Reference --- p.64

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

No description available.

Dense wavelength division multiplexing (DWDM) is becoming the technology of choice for meeting the increasing bandwidth demands in optical networks. DWDM has been used to increase the capacity of long-haul optical transport systems. Efforts are being made to move DWDM into the broadband access network serving residential and business subscribers. First, a new centralized DWDM PON scheme is demonstrated for bi-directional upstream and downstream transmissions. The proposed DWDM PON scheme is implemented using optical carrier suppression and separation (OCSS) technology to generate a wavelength pair from a single laser source at the central office. This method enables the co-location of both upstream and downstream DWDM transmitters in the central office. In addition, the complexity, cost, and maintenance of the optical network unit are reduced by enabling wavelength independent operation. Second, a new multistage architecture is proposed for the delivery of information to groups of subscribers located at different distances from the central office. A 25 GHz DWDM comb is generated using OCSS technology, and error-free transmission of four 10 Gbps channels is demonstrated. Finally, a new wide area access network with bi-directional DWDM amplification using semiconductor optical amplifiers (SOAs) is demonstrated. The detrimental effect of SOA crosstalk resulting from cross gain modulation can be suppressed using a constant intensity modulation format such as differential phase shift keying (DPSK). The feasibiity of bi-directional DPSK transmission of 16 interleaved DWDM channels using an in-line SOA has been studied experimentally. In addition, the reduction of bi-directional SOA reflections has been realized by optimizing the SOA bias current and facet reflectivities.