The demand for faster data transmission is ever increasing. Wavelength division multiplexing (WDM) presents as a viable solution to increase the data transmission rate significantly. WDM systems are based on the ability to transmit multiple wavelengths simultaneously down the fibre. Unlike time division multiplexing (TDM) systems, WDM systems do not increase the data transfer by increasing the transmission rate of a single channel. In WDM systems the data rate per channel remains the same, only multiple channels carry data across the link. Dense wavelength division multiplexing (DWDM) promises even more wavelengths packed together in the same fibre. This multiplication of channels increases the bandwidth capacity rapidly. Networks are looking into making use of technology that will ensure no electronic signal regeneration at any point within the DWDM network. Examples are; reconfigurable optical add/drop multiplexers (ROADM) and optical cross connect (OXC) units. These components essentially enable network operators to split, combine and multiplex optical signals carried by optical fibre. WDM allows network operators to increase the capacity of existing networks without expensive re-cabling. This provides networks with the flexibility to be upgraded to larger bandwidths and for reconfiguration of network services. Further, WDM technology opens up an opportunity of marketing flexibility to network operators, where operators not only have the option to rent out cables and fibres but wavelengths as well. Cross phase modulation (XPM) poses a problem to WDM networks. The refractive index experienced by a neighbouring optical signal, not only depends on the signal’s intensity but on the intensity of the co-propagating signal as well. This effect leads to a phase change and is known as XPM. This work investigates the characteristics of XPM. It is shown that, in a two channel WDM network, a probe signal’s SOP can be steered by controlling a high intensity pump signal’s SOP. This effect could be applied to make a wavelength converter. Experimental results show that the degree of polarization (DOP) of a probe signal degrades according to a mathematical model found in literature. The pump and probe signals are shown to experience maximum interaction, for orthogonal probe-pump SOP vector orientations. This may be problematic to polarization mode dispersion compensators. Additionally, experimental results point out that the SOP of a probe signal is much more active in the presence of a high intensity pump, as compared to the single signal transmission scenario.

L’objet de cette thèse est l’étude de la distribution quantique de clés, une primitive cryptographique qui permet à deux utilisateurs distants de générer une quantité arbitraire de clé secrète et cela y compris en présence d’un espion, sous réserve qu’ils partagent un secret initial. Nous restreignons notre étude aux protocoles employant des variables continues et démontrons expérimentalement une implémentation entièrement fibrée fonctionnant à 80 km sur une fibre dédiée en prenant en compte toutes les imperfections expérimentales connues. Pour atteindre une telle distance de fonctionnement, nous avons mis au point des codes correcteurs d’erreurs spécifiques fonctionnant près de la limite théorique de Shannon dans des régimes de faible rapport signal à bruit. Nous envisageons également la possibilité d’attaques par canaux cachés qui ne sont donc pas prises en compte dans la preuve de sécurité du système et proposons des contre-mesures. Enfin, nous étudions la compatibilité de notre système avec des canaux de communication intenses qui se propagent sur la même fibre optique. / This thesis focuses on a cryptographic primitive that allows two distant parties to generate an arbitrary amount of secret key even in the presence of an eavesdropper, provided that they share a short initial secret message. We focus our study on continuous-variable protocols and demonstrate experimentally an all-fiber system that performs distribution of secret keys at 80 km on a dedicated fiber link while taking into account all known imperfections. We could extract secret keys at such a distance bydesigning specific error correcting codes that perform very close to Shannon’s bound for low signal to noise ratios. We also consider side-channel attacks that are not taken into account into the system security proof and propose some countermeasures. Finally, we study our system compability with intense communication channels that propagate on the same optical fiber.

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.

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

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

Zhang Yu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 67-72). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview of Optical Networking --- p.1 / Chapter 1.2 --- Mechanism in Optical Routing Networks --- p.3 / Chapter 1.3 --- Related Work on Optical Routing Networks --- p.4 / Chapter 1.4 --- The Motivation of This Thesis --- p.7 / Chapter 1.5 --- Thesis Structure --- p.8 / Chapter 2 --- Technologies for Multi-dimensional Optical Routing Networks --- p.10 / Chapter 2.1 --- Background --- p.10 / Chapter 2.2 --- Multi-fiber WDM Networks --- p.11 / Chapter 2.2.1 --- Phased-Array-Based WDM Device --- p.11 / Chapter 2.2.2 --- Wavelength-tunable lasers --- p.11 / Chapter 2.2.3 --- Tunable optical Filter --- p.12 / Chapter 2.2.4 --- Wavelength Converter --- p.13 / Chapter 2.3 --- OCDM/WDM --- p.16 / Chapter 2.3.1 --- Optical En/Decoder --- p.17 / Chapter 2.3.2 --- Optical Switch --- p.18 / Chapter 2.3.3 --- Optical Code Conversion --- p.18 / Chapter 2.4 --- OTDM/WDM --- p.21 / Chapter 2.4.1 --- Fast Optical Switch --- p.22 / Chapter 2.4.2 --- Optical Time Slot Interchanger (OTSI) --- p.22 / Chapter 2.5 --- Conclusion --- p.23 / Chapter 3 --- Performance of Code/Wavelength Routing Networks --- p.24 / Chapter 3.1 --- Background --- p.24 / Chapter 3.2 --- Reconfiguration Capability --- p.25 / Chapter 3.3 --- Analytic Models --- p.27 / Chapter 3.3.1 --- Trunk Switched Model --- p.27 / Chapter 3.3.2 --- Assumptions --- p.28 / Chapter 3.3.3 --- Blocking of the Paths with Various Configurations --- p.29 / Chapter 3.4 --- Numerical Results --- p.34 / Chapter 3.5 --- Conclusion --- p.35 / Chapter 4 --- Decomposition Schemes --- p.40 / Chapter 4.1 --- Introduction --- p.40 / Chapter 4.2 --- Inclusive Converted Networks --- p.41 / Chapter 4.3 --- Decompositions --- p.43 / Chapter 4.3.1 --- Spatial Decomposition (S.D.) --- p.43 / Chapter 4.3.2 --- Dimensional Decomposition (D.D.) --- p.44 / Chapter 4.3.3 --- Iterative Decompositions --- p.45 / Chapter 4.4 --- Conclusion --- p.46 / Chapter 5 --- Performance of Multi-Dimensional Optical Routing Networks --- p.48 / Chapter 5.1 --- Homogeneous Trunk Switched Networks --- p.48 / Chapter 5.2 --- Analytical Model --- p.49 / Chapter 5.3 --- Utilization Gain --- p.53 / Chapter 5.4 --- Conversion Gain --- p.54 / Chapter 5.5 --- Comparison on the Utilization Gain by Multiplexing and by Conversion --- p.56 / Chapter 5.6 --- Conclusion --- p.57 / Chapter 6 --- Conclusion --- p.65 / Chapter 6.1 --- Summary of the Thesis --- p.65 / Chapter 6.2 --- Future Work --- p.66

Silicon photonics has emerged in recent years as one of the leading technologies poised to enable penetration of optical communications deeper and more intimately into computing systems than ever before. The integration potential of power efficient WDM links at the first level package or even deeper has been a strong driver for the rapid development this field has seen in recent years. The integration of photonic communication modules with very high bandwidth densities and virtually no bandwidth-distance limitations at the short reach regime of high performance computers and data centers has the potential to alleviate many of the bandwidth bottlenecks currently faced by board, rack, and facility levels. While networks on chip for chip multiprocessors (CMP) were initially deemed the target application of silicon photonic components, it has become evident in recent years that the initial lower hanging fruit is the CMP's I/O links to memory as well as other CMPs. The first chapter of the thesis provides more detailed motivation for the integration of silicon photonic modules into compute systems and surveys some of the recent developments in the field. The second chapter then proceeds to detail a technical case study of silicon photonic microring-based WDM links' scalability and power efficiency for these chip I/O applications which could be developed in the intermediate future. The analysis, initiated originally for a workshop on optical and electrical board and rack level interconnects, looks into a detailed model of the optical power budget for such a link capturing both single-channel aspects as well as WDM-operation-related considerations which are unique for a microring physical characteristics. The holistic analysis for the full link captures the wavelength-channel-spacing dependent characteristics, provides some methodologies for device design in the WDM-operation context, and provides performance predictions based on current best-of-class silicon photonic devices. The key results of the analysis are the determination of upper bounds on the aggregate achievable communication bandwidth per link, identifying design trade-offs for bandwidth versus power efficiency, and highlighting the need for continued technological improvements in both laser as well as photodetector technologies to allow acceptable power efficiency operation of such systems.The third chapter, while continuing on the theme silicon photonic high bandwidth density links, proceeds to detail the first experimental demonstration and characterization of an on-chip spatial division multiplexing (SDM) scheme based on microrings for the multiplexing and demultiplexing functionalities. In the context of more forward looking optical network-on-chip environments, SDM-enabled WDM photonic interconnects can potentially achieve superior bandwidth densities per waveguide compared to WDM-only photonic interconnects. The microring-based implementation allows dynamic tuning of the multiplexing and demultiplexing characteristic of the system which allows operation on WDM grid as well device tuning to combat intra-channel crosstalk. The characterization focuses on the first reported power penalty measurements for on-chip silicon photonic SDM link showing minimal penalties achievable with 3 spatial modes concurrently operating on a single waveguide with 10-Gb/s data carried by each mode. The chapter also details the first demonstration of WDM combined with SDM operation with six separate wavelength-and-spatial 10-Gb/s channels with error free operation and low power penalties. The fourth, fifth, and sixth chapters shift in topic from the application of silicon photonics to communication links to the evolving use of silicon waveguides for nonlinear all-optical processing. The unique tight mode confinement in sub-micron cross-sections combined with the high response of silicon have motivated the development of four-wave mixing (FWM)-based processing silicon devices. The key feature of the silicon platform for these nonlinear processing platforms is the ability to finely and uniformly control the dispersive properties of the optical structures in a way that enables completely offsetting the material dispersion and achieve dispersion profiles required for effective parametric interaction of waves in the optical structures. Chapter four primarily introduces and motivates nonlinear processing in communication applications and focuses on recent achievements in non-silicon and silicon FWM platforms. Chapter five describes some of the author's contributions on parametric processing of high speed data in silicon nonlinear devices, with first of a kind demonstrations of wavelength conversion of 160-Gb/s optically time division multiplexed (OTDM) data as well as the wavelength-multicasting of a 320-Gb/s OTDM stream. The chapter then details a methodical characterization and demonstration of several record wavelength conversion experiments of data in silicon with 40-Gb/s data wavelength-converted across more than 100 nm with only 1.4-dB of power penalties as well as the wavelength and format conversion of 10-Gb/s data across up to 168 nm with sensitivity gains stemming from the format conversion of about 2 dB and a residual conversion penalty of only 0.1 dB, achieved by implementing an improved experimental setup. Both experiments highlight the performance uniformity of the conversion process for a wide range of probe-idler detuning settings, showcasing the silicon platform's unique broadband phase matching properties. The sixth chapter presents a slight shift in motivation for parametric processing from traditional telecom-wavelength applications to functionalities developed targeting mid-IR operation. Parametric-processing in the silicon platform at long wavelengths holds large potential for performance improvements due to the elimination of two-photon absorption in silicon at long wavelengths as well as silicon's dispersion engineering capabilities which uniquely position the silicon platform for effective phase matching of significantly wavelength detuned waves. Four-wave mixing signal generation and reception at mid-IR wavelengths are attractive candidates for tunable flexible operation with modulation and detection speeds which are currently only available at telecom wavelengths. With this vision in mind, several contributions detailing extension of FWM functionalities in silicon to operate at wavelengths close to 2 μm with performance equivalent to much smaller detuning setting measurements. The contributions detail the experimental demonstration of the first silicon optical processing functionalities achieved at such long wavelengths including the wavelength conversion and unicast of 10-Gb/s signals with up to 700 nm of probe-idler detuning, the combined two-stage 10-Gb/s FWM-link in which both data generation and detection at 1900 nm is facilitated by parametric processing in silicon with only 2.1-dB overall penalty, the first ever 40-Gb/s receiver at 1900 nm based on a FWM stage for simultaneous temporal demultiplexing and wavelength conversion, and lastly, the demonstration of a 40-Gb/s FWM-link operation with only 3.6 dB of penalty. The chapter concludes with a short discussion on possible extensions to enable silicon parametric processing at even longer wavelengths targeting the mid-IR spectral transmission window of 3-5 μm.

Zhao Jian. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 61-68). / Abstracts in English and Chinese. / Chapter 1. --- INTRODUCTION --- p.1 / Chapter 1.1. --- Applications Background - wdm Transmission Systems --- p.1 / Chapter 1.1.1. --- Long-haul WDM Transmission Systems --- p.3 / Chapter 1.1.2. --- OTDM/WDM Transmission Systems --- p.4 / Chapter 1.2. --- Spectrum-slicing Multi-wavelength Sources --- p.6 / Chapter 1.3. --- Introduction of Super-continuum Generation --- p.9 / Chapter 1.4. --- Outline of this Thesis --- p.13 / Chapter 2. --- PRINCIPLES OF SUPER-CONTINUUM GENERATION --- p.15 / Chapter 2.1. --- Super-continuum in Anomalous Dispersive Fiber --- p.17 / Chapter 2.2. --- Super-continuum in Dispersion Decreasing Fiber --- p.21 / Chapter 2.3. --- super-continuum in normal dispersive fiber --- p.23 / Chapter 2.4. --- Super-continuum in Dispersion Flattened and Dispersion Decreasing Fiber --- p.25 / Chapter 2.5. --- Conclusions --- p.27 / Chapter 3. --- OPTIMAL ANALYSIS OF SUPER-CONTINUUM SOURCES OPERATING IN NORMAL DISPERSIVE FIBERS --- p.29 / Chapter 3.1. --- Numerical Model --- p.31 / Chapter 3.2. --- Broadened Spectrum Width --- p.33 / Chapter 3.2.1. --- Broadened Spectrum Width without High-order Dispersion and High-order Nonlinearities --- p.33 / Chapter 3.2.2. --- Influence of High-order Dispersion and High-order Nonlinearities --- p.37 / Chapter 3.3. --- Quality of the Pulses Sliced from SC Spectrum --- p.40 / Chapter 3.3.1. --- Principles --- p.40 / Chapter 3.3.2. --- Influence of Some Parameters on the System Performance of SC Sources --- p.49 / Chapter 3.3.2.1. --- Influence of N --- p.49 / Chapter 3.3.2.2. --- Influence of the Slicing Filter Width --- p.52 / Chapter 3.3.2.3. --- Influence of the Input Peak Power --- p.55 / Chapter 3.4. --- Conclusions --- p.57 / Chapter 4. --- SUMMARY AND FUTURE WORK --- p.59 / BIBLIOGRAPHY --- p.61 / APPENDIX-PUBLICATIONS --- p.68

如今，隨著信息爆炸，骨幹網絡和城域網絡的容量需求已成倍增加。因此，如何提高網絡容量正成為學術界和工業界的熱門話題。可變帶寬光網絡技術通過為不同速率的數據傳輸分配剛剛足夠的帶寬來提高網絡容量，而物理層網絡編碼技術（PNC）在沒有復雜的硬件要求下可以增加網絡容量。在這篇論文中，我們首先提出將組播應用於可變帶寬光網絡來提高網絡容量。我們進一步提出將物理層網絡編碼技術應用於時分複用光接入網絡（TDM-PON），從而來提高全光虛擬專用通信（VPN）的網絡容量。 / 可變帶寬光網絡中組播的分析 / 可變帶寬光網絡相比傳統的波分複用光網絡（WDM）可以提高骨幹網絡的頻譜利用率，因為它可以靈活地分配剛剛足夠的帶寬。另一方面，光網絡層上的組播是一種高效的支持點對多點的通信技術。在未來的許多寬帶服務中，點對多點應用服務是必不可少的，通過光組播技術可以節省頻譜帶寬和接發器的數目。為了進一步提高網絡容量，我們建議在可變帶寬光網絡中進行組播。雖然關於可變帶寬光網絡的研究已經有很多了，但據我們所知，關於可變帶寬光網絡的組播尚未被研究。我們通過兩種有效算法來解決可變帶寬光網絡組播的路由和頻譜分配問題。採用相同的路由和波長/頻譜分配算法，我們研究了有靈活帶寬分配產生的好處，通過比較可變帶寬光網絡和傳統波分複用網絡的組播。我們也探討了由非均勻帶寬分配造成的頻譜間隙對提高網絡容量的影響。 / 時分複用光接入網中(TDM-PON)的物理層網絡編碼技術（PNC） / 網絡編碼是一種很有前途的技術，可以提高網絡的容量和健全性。雖然最近有關於在時分複用光接入網中進行網絡編碼的研究，應用於同一個光接入網絡中的光網絡單元（ONU）之間的通信，但在這些研究中的最大的網絡容量提高只有33。此外，在光網路終端（OLT）和光網絡單元中還需要大量的緩衝來存儲VPN數據。在時分複用光接入網中，全光VPN網絡可以重新將VPN數據傳送到相應的ONU，實現ONU之間的直接通信，不需要在OLT進行光-電-光的轉換。在這裡，據我們所知，我們第一次用實驗驗證了一種新方案，將物理層網絡編碼技術應用於TDM-PON，使得全光VPN通信的網絡容量增加了一倍。我們也提出了在光接入網中的遠程節點處使用光環路器，以此減少VPN通信的插入損耗。當兩個ONU之間需要進行雙向通信，可以通過利用PNC來實現全雙工傳輸，相比傳統半雙工的全光VPN方案，網絡容量可以提高100。實驗結果表明，可以實現無差錯全雙工VPN通信，相比半雙工通信功率補償不超過3分貝，而且這方案中ONU間的同步是不需要的。 / Nowadays, with the information explosion, the capacity demand has been exponentially increasing in backbone networks and metro networks. Therefore, it is becoming a hot topic for both academic and industry to improve the network capacity. Elastic technologies are promising to scale up the network capacity due to just-enough bandwidth allocation for different data-rate traffic request, while physical-layer network coding (PNC) can increase the throughput without complex requirement on hardware. In this thesis, we first propose a novel scheme to improve the network capacity by implementing multicast in elastic optical networks. We further present the capacity improvement by integrating PNC in time-division multiplexing passive optical network (TDM-PON) for all-optical virtual private network (VPN) communications. / Analysis of multicast in elastic optical networks / Elastic optical networks can increase the spectrum utilization of backbone networks compared to the traditional wavelength-division multiplexing (WDM) networks due to flexible and just-enough bandwidth allocation. On the other hand, multicast over the optical layer is a bandwidth-efficient communication technique which supports point-to-multipoint applications. As many broadband services in the future can be from one source to several destinations, it is essential to enable optical multicast to save bandwidth as well as transceivers. To further improve the network throughput, we propose to implement multicast in spectrum elastic optical networks. Although many investigations on elastic optical networks have been carried out, to the best of our knowledge, the performance of multicast in elastic optical networks have not yet been studied. We develop two efficient multicast heuristics to solve the multicast routing and spectrum allocation (MC-RSA) problem in elastic optical networks. By adopting the same routing and wavelength/spectrum allocation algorithms, the benefits of elastic optical networks resulting from flexible bandwidth allocation are studied for multicast compared to the traditional WDM networks. We also investigate the impact of spectral gap caused by non-uniform bandwidth allocation on the improvement of network throughput. / Physical-layer network coding (PNC) in TDM-PON / Network coding is a promising technique to improve the network throughput and robustness. Although network coding in TDM-PON has been recently investigated for exchanging information among optical network units (ONUs) in the same PON, the maximum capacity improvement of inter-ONU communications in these schemes is only 33%. In addition, large electrical buffer is required to store the VPN traffic at both optical line terminal (OLT) and ONUs. All-optical VPN in TDM-PON can optically reroute VPN traffic to the destined ONU without optical-electrical-optical conversion at OLT, which enables direct communications among ONUs. Here, to the best of our knowledge, for the first time, we experimentally demonstrate a novel PNC scheme integrated in TDM-PON for all-optical VPN communications to double the network throughput. A unique remote node that uses optical circulators to reduce the insertion loss of VPN communications is also proposed. By transmitting two inter-ONU traffic streams of opposite direction simultaneously using PNC (full-duplex), it can improve the network throughput by 100% compared to the traditional all-optical VPN schemes (half-duplex). Experiments show that error-free full-duplex VPN communications are achieved, and the power penalty is no more than 3 dB. Synchronization of ONUs is not required for the proposed scheme. / 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. / Wang, Qike. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 43-48). / Abstracts also in Chinese. / Chapter Chapter 1 --- Background --- p.1 / Chapter 1.1 --- Elastic optical networks --- p.1 / Chapter 1.2 --- Multiscast in WDM networks --- p.5 / Chapter 1.3 --- Network coding in passive optical network (PON) --- p.7 / Chapter 1.4 --- All-optical virtual private nework (VPN) in PON --- p.11 / Chapter 1.5 --- Contribution of this thesis --- p.13 / Chapter 1.6 --- Organization of this thesis --- p.15 / Chapter Chapter 2 --- Analysis of multicast in elastic optical networks --- p.16 / Chapter 2.1 --- Introduction --- p.16 / Chapter 2.2 --- Network model and heuristics --- p.18 / Chapter 2.2.1 --- Multicast-capable node architecture --- p.18 / Chapter 2.2.2 --- Multicast goup size (MGS) factor --- p.19 / Chapter 2.2.3 --- Network resource and assumption --- p.19 / Chapter 2.2.4 --- Multicast routing and spectrum allocation (MC-RSA) heuristics --- p.20 / Chapter 2.3 --- Numerical results --- p.22 / Chapter 2.4 --- Summary --- p.27 / Chapter Chapter 3 --- Physical-layer network coding (PNC) in TDM-PON --- p.28 / Chapter 3.1 --- Introduction --- p.28 / Chapter 3.2 --- A novel PNC in TDM-PON scheme for all-optical VPN applications --- p.31 / Chapter 3.2.1 --- System architecture --- p.31 / Chapter 3.2.2 --- Implementation of PNC --- p.32 / Chapter 3.2.3 --- Management of wavelength collision --- p.33 / Chapter 3.3 --- Experiemnts and results --- p.35 / Chapter 3.4 --- Summary --- p.39 / Chapter Chapter 4 --- Conclusion and Future Works --- p.40 / Chapter 4.1 --- Conclusion of this thesis --- p.40 / Chapter 4.2 --- Future works --- p.41 / Bibliography --- p.43 / List of Publications --- p.50