Experimental comparison of impairment-aware RWA algorithms in a GMPLS-controlled dynamic optical network

The European research project DICONET proposed and implemented a multi-plane impairment-aware solution for flexible, robust and cost-effective core optical networks. The vision of DICONET was realized via a set of cross-layer optimization algorithms designed to serve the network during planning and operation. The cross-layer modules were incorporated in a common software platform forming a planning and operation tool that takes into account physical-layer impairments in the decision making. The overall solution relies on a GMPLS-based control plane that was extended to disseminate the physical layer information required by the cross-layer modules. One of the key activities in DICONET concerns the routing and wavelength assignment of traffic demands that arrive dynamically during the network operation. Identifying the important role of dynamic lightpath provisioning, in this work we focused on the performance of routing algorithms in dynamic optical networks. We tested the suitability and performance of two different online IA-RWA algorithms in a 14-node experimental test-bed that employed centralized control-plane architecture under the same network and traffic conditions. The parameters used to evaluate the two routing engines included the lightpath setup time and the blocking ratio in a traffic scenario where connections arrive and depart from the network dynamically. Results for different traffic loads showed that optimum impairment-aware decisions are made at the expense of higher lightpath setup times.Postprint (published version

Cross-Layer Platform for Dynamic, Energy-Efficient Optical Networks

The design of the next-generation Internet infrastructure is driven by the need to sustain the massive growth in bandwidth demands. Novel, energy-efficient, optical networking technologies and architectures are required to effectively meet the stringent performance requirements with low cost and ultrahigh energy efficiencies. In this thesis, a cross-layer communications platform is proposed to enable greater intelligence and functionality on the physical layer. Providing the optical layer with advanced networking capabilities will facilitate the dynamic management and optimization of optical switching based on performance monitoring measurements and higher-layer attributes. The cross-layer platform aims to create a new framework for networks to incorporate packet-scale measurement subsystems and techniques for monitoring the health of the optical channel. This will allow for quality-of-service- and energy-aware routing schemes, as well as an enhanced awareness of the optical data signals. This thesis first presents the design and development of an optical packet switching fabric. Leveraging a networking test-bed environment to validate networking hypotheses, advanced switching functionalities are demonstrated, including the support for quality-of-service based routing and packet multicasting. The investigated cross-layering is based on emerging optical technologies, enabling packet protection techniques and packet-rate switching fabric reconfiguration. Coupled with fast performance monitoring, the platform will achieve significant performance gains within the endeavor of all-optical switching. Allowing for a more intelligent, programmable optical layer aims to support greater flexibility with respect to bandwidth allocation and potentially a significant reduction in the network's energy consumption. The ultimate deliverable of this work is a high-performance, cross-layer enabled optical network node. The experimental demonstration of an initial prototype creates a dynamic network element with distributed control plane management, featuring fast packet-rate optical switching capabilities and embedded physical-layer performance monitoring modules. The cross-layer box enables an intelligent traffic delivery system that can dynamically manipulate optical switching on a packet-granular scale. With the goal of achieving advanced multi-layer routing and control algorithms, the network node requires an intelligent co-optimization across all the layers. The proposed cross-layer design should drive optical technologies and architectures in an innovative way, in order to fulfill the void between the design of basic photonic devices and the networking protocols that use them. The performance of the entire network -- from the optical components, to the routing algorithms and user applications -- should be optimized in concert. This contribution to the area of cross-layer network design creates an adaptable optical pipe that is extremely flexible and intelligent aware of both the physical optical signals and higher-layer requirements. The impact of this work will be seen in the realization of dynamic, energy-efficient optical communication links in future networking infrastructures

Field test of quantum key distribution in the Tokyo QKD Network

A novel secure communication network with quantum key distribution in a metropolitan area is reported. Different QKD schemes are integrated to demonstrate secure TV conferencing over a distance of 45km, stable long-term operation, and application to secure mobile phones.Comment: 21 pages, 19 figure

Survivability aspects of future optical backbone networks

In huidige glasvezelnetwerken kan een enkele vezel een gigantische hoeveelheid data dragen, ruwweg het equivalent van 25 miljoen gelijktijdige telefoongesprekken. Hierdoor zullen netwerkstoringen, zoals breuken van een glasvezelkabel, de communicatie van een groot aantal eindgebruikers verstoren. Netwerkoperatoren kiezen er dan ook voor om hun netwerk zo te bouwen dat zulke grote storingen automatisch opgevangen worden. Dit proefschrift spitst zich toe op twee aspecten rond de overleefbaarheid in toekomstige optische netwerken. De eerste doelstelling die beoogd wordt is het tot stand brengen vanrobuuste dataverbindingen over meerdere netwerken. Door voldoende betrouwbare verbindingen tot stand te brengen over een infrastructuur die niet door een enkele entiteit wordt beheerd kan men bv. weredwijd Internettelevisie van hoge kwaliteit aanbieden. De bestudeerde oplossing heeft niet enkel tot doel om deze zeer betrouwbare verbinding te berekenen, maar ook om dit te bewerkstelligen met een minimum aan gebruikte netwerkcapaciteit. De tweede doelstelling was om een antwoord te formuleren om de vraag hoe het toepassen van optische schakelsystemen gebaseerd op herconfigureerbare optische multiplexers een impact heeft op de overleefbaarheid van een optisch netwerk. Bij lagere volumes hebben optisch geschakelde netwerken weinig voordeel van dergelijke gesofistikeerde methoden. Elektronisch geschakelde netwerken vertonen geen afhankelijkheid van het datavolume en hebben altijd baat bij optimalisatie

저전압에서 구동 가능한 전 용액 공정 기반 플렉시블 폴리머 발광다이오드에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2019. 2. 홍용택.In this Ph.D. dissertation, I fabricated all solution-processed flexible polymer light emitting diodes (PLEDs) under low-operation voltage which are potentially of interest in the application to low-cost and large-area mass production of future display. In recent years, although many groups have reported all solution-processed PLEDs via various manufacturing methods such as spin coating, inkjet printing and transfer printing, there are still remaining rooms for further improvement to realize the commercial products in terms of customizability and power consumption. First, formation of additional layers via a solution process on a hydrophobic emission layer (EML) is difficult due to an extremely poor wetting property. Among the methods to improve the wetting property of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole injection layer (HIL) in various optoelectronic devices such as surfactant addition into the original solution, surface treatment of organic underlying layers and dilution with a low surface tension, the dilution method is the most promising approach because it changes only surface tension of the PEDOT:PSS solution without causing any degradation of the organic layer or device. Using the optimized dilution condition with ethanol, the PEDOT:PSS HIL was coated uniformly on the hydrophobic EML. Based on these results, I fabricated the inverted PLEDs with solution-processed multi-layers, especially the PEDOT:PSS HIL on the EML, sandwiched between the sputtered indium tin oxide (ITO) and evaporated Al electrodes. In particular, the uniformly coated PEDOT:PSS HIL plays an important role for high device performance and light emission uniformity on one substrate. Second, it is necessary to replace the vacuum-processed electrodes to the solution-processed electrodes in order to achieve all solution-processed PLEDs. In the early works about all solution-processed PLEDs, however, the complicated and high-cost fabrication, especially in forming both electrodes, limits their development of the cost-effective and large-area commercial display products. For simple pixel definition, the electrodes of the PLEDs should be patterned easily with a high degree of freedom, but the previous works have utilized unproductive electrode deposition methods while demonstrating only one or a few devices on one substrate. In addition, when solvent orthogonality is not satisfied, solvents can damage the underlying layers during the solution process, resulting in the degradation of the device performance. To solve these issues, I integrated the inkjet printing and transfer printing in forming a conductive PEDOT:PSS film, which enables a facile pattering of electrodes and minimal solvent damages, simultaneously. For the successful transfer printing of PEDOT:PSS, I modulated the as-purchased PEDOT:PSS solution by adding a D-sorbitol solution to give the adhesive force to the film and carefully controlled an adhesive force between the film and each substrate such as donor quartz, polydimethylsiloxane (PDMS) stamp and target substrates. Based on these results, I applied the transferred PEDOT:PSS electrodes to top anodes of all solution-processed inverted PLEDs with the well-defined functional layers via the spin coating on the inkjet-printed Ag cathodes. My rigid and flexible devices showed a high device efficiency and operated normally even under a bending state in the case of those on the plastic substrate. Using the maskless patterning for both Ag and PEDOT:PSS electrodes via the inkjet printing, the customized PLEDs and their array were manufactured with various pixel shapes and fine lines. In particular, for the first time, I demonstrated 5×7 passive matrix PLEDs (PMPLEDs) with a 500 μm pixel width using all solution processing, displaying a variety of characters without any crosstalk. Third, a low conductivity of electrodes in the devices can cause severe voltage drop and high power consumption during the device operation. My devices also have suffered from the low power efficiency which comes from a high sheet resistance of the transferred PEDOT:PSS electrodes. Therefore, I need to fabricate highly transparent and conductive flexible electrodes for the low-voltage driven flexible electronics including all solution-processed PLEDs while avoiding a complicated fabrication process at the same time. I introduced a facile pattering method of high-performance flexible electrodes by integrating the inkjet printing of the PEDOT:PSS transfer medium and selective transfer of silver nanowire (AgNW) networks only onto the region of the transfer medium. First, for the successful AgNW transfer, I formulated the blended PEDOT:PSS ink with the D-sorbitol aqueous solution to strongly attach the PEDOT:PSS and AgNW networks. Afterwards, it was inkjet-printed on arbitrary substrates with a desired pattern, thereby obtaining the customized PEDOT:PSS transfer medium. Second, I fabricated highly conductive and transparent AgNW networks on the plasma-treated PDMS stamp by the spin coating. Finally, I conducted the heat treatment for the attached sample of the existing substrate with the PEDOT:PSS film and AgNW-coated PDMS stamp, which results in selective transfer of the AgNW networks and thus highly customizable AgNW-transferred PEDOT:PSS film. Based on these principles, my AgNW-transferred PEDOT:PSS electrodes were formed on the various substrates according to the purpose of use, showing not only excellent optoelectronic properties but also fine lines with hundreds of micrometers in width. In addition, their electrical and optical properties were highly tunable by controlling the AgNW coating conditions and the previous issues of the AgNWs such as a high surface roughness and weak adhesion with the substrate were overcome by the partially embedded AgNWs in the PEDOT:PSS matrix. In the plastic substrate, my AgNW-transferred PEDOT:PSS electrodes showed not only more excellent optoelectronic properties but also more outstanding mechanical flexibility compared to ITO. Employing my flexible electrodes, I exhibited several applications of the customized flexible electronics such as light-emitting diode (LED) arrays and all solution-processed PLEDs. In particular, the low-voltage driven PLEDs exhibited a low operating voltage while maintaining the optical performance.본 논문에서는 미래 디스플레이 구현을 위한 저비용 및 대면적의 대량 생산 가능성을 보여 주는 저전압에서 구동 가능한 전 용액 공정 기반의 플렉시블 폴리머 발광다이오드를 제작하였다. 최근 많은 연구 그룹에서 스핀 코팅, 잉크젯 프린팅, 트랜스퍼 프린팅과 같은 다양한 공정 방법으로 전 용액 공정 기반의 폴리머 발광다이오드를 보고하고 있지만, 맞춤 제작과 저전력 소비 면에서 제품으로의 상업화를 위해선 많은 개선 사항들이 존재하고 있다. 첫 번째로, 소수성인 발광층 위에 용액 공정으로 추가 층을 형성하는 것은 웨팅 특성의 불일치로 어려움을 겪고 있다. 다양한 광학 소자에서 PEDOT:PSS 정공 주입층의 웨팅 특성을 향상시키기 위해, 계면 활성제 추가, 유기 하부 층에 대한 표면 처리, 낮은 표면 장력을 가지는 용액과 희석 방법 등이 보고 되고 있는데, 이러한 방법들 중에서 희석 방법이 유기 층이나 전체 소자에 어떠한 손상을 일으키지 않으면서 용액의 표면 장력만 바꾼다는 점에서 이점을 가진다. 에탄올과의 최적화된 희석 농도를 통해, PEDOT:PSS 정공 주입층이 소수성인 발광층 위에 균일하게 코팅 되었다. 이 방법을 이용해 스퍼터링 된 ITO와 증착 된 알루미늄 전극 사이에 소수성 발광층 위 PEDOT:PSS 정공 주입층을 포함하는 용액 공정 기반 다층 구조의 역방향 폴리머 발광다이오드를 제작하였다. 위 소자에서 균일하게 형성된 PEDOT:PSS 정공 주입층은 소자의 특성 향상 및 한 기판 내에서의 균일한 발광 특성에 있어서 중요한 역할을 한다. 두 번째로, 전 용액 공정 기반의 폴리머 발광다이오드를 제작하기 위해 기존에 사용된 진공 증착 방식의 전극을 용액 공정 방식의 전극으로 교체할 필요가 있다. 이러한 소자에 대한 많은 연구들이 보고되고 있지만, 양 전극을 형성하는데 있어 복잡하고 고비용의 제작 방식은 저비용 및 대면적 디스플레이 상품 개발에 있어 적합하지 않다. 간편한 픽셀 형성을 위해 폴리머 발광다이오드의 전극은 쉽고 자유롭게 패터닝이 되어야 하지만, 기존의 연구들은 하나의 소자 데모를 위한 목적으로만 비생산적인 전극 패터닝 기술을 사용하였다. Solvent orthogonality 또한 충족이 되어야 용액 공정 시 발생할 수 있는 하부 층의 손상을 막음으로써, 소자 특성의 저하를 방지할 수 있다. 위의 두 문제를 해결하기 위해 잉크젯 프린팅과 트랜스퍼 프린팅 방식의 조합을 통한 전도성 PEDOT:PSS 층을 형성하여 전극에 대한 간편한 패터닝을 달성하고 용액에 의한 소자의 손상을 최소화 하였다. 트랜스퍼 된 PEDOT:PSS 층을 얻기 위해, D-sorbitol 용액을 PEDOT:PSS 용액에 첨가해 접착력이 있는 층을 형성하였고, PEDOT:PSS 층과 donor quartz, PDMS 스탬프, target 기판 각각과의 접착력을 조절하였다. 이 방법을 이용하여 트랜스퍼 된 PEDOT:PSS 전극을 잉크젯 프린팅 된 실버 음극 위 스핀코팅으로 형성된 기능층을 가지는 전 용액 공정 기반 역방향 폴리머 발광다이오드의 상부 양극으로 적용하였다. 단단한 그리고 유연한 소자는 고성능을 보여줄 뿐만 아니라 구부러짐 상태에서도 정상적으로 동작하였다. 또한 잉크젯 프린팅을 통한 실버와 PEDOT:PSS 전극의 마스크가 필요 없는 패터닝 기술을 이용하여 다양한 픽셀 모양과 얇은 라인을 가지는 주문 제작된 발광다이오드와 어레이를 제작하였다. 특히 전 용액 공정 기반의 500 마이크로미터 픽셀 너비를 가지는 5×7 패시브 매트릭스 폴리머 발광다이오드가 처음으로 데모 되었으며, 픽셀 간 crosstalk 없이 다양한 글자를 표시하였다. 세 번째로, 전극의 낮은 전도성은 소자가 동작하는 동안 큰 전압 강하에 따른 높은 소비 전력을 요구하게 한다. 앞서 제작한 소자 또한 트랜스퍼 된 PEDOT:PSS 전극의 높은 면저항으로 인해 낮은 전력 효율을 보여주고 있다. 따라서 복잡한 공정 방식이 아닌 간단한 방법으로 전 용액 공정 발광다이오드를 포함하는 저전압 구동이 가능한 플렉시블 전자 소자로의 응용을 위한 고성능의 플렉시블 전극을 개발할 필요가 있었다. 이에 본 저자는 PEDOT:PSS 트랜스퍼 매개체에 대한 잉크젯 프린팅과 실버 나노와이어의 트랜스퍼 매개체 위로만의 선택적 트랜스퍼 기술을 융합하여 고성능 플렉시블 전극에 대한 간단한 패터닝 방법을 개발하였다. 첫 번째로 실버 나노와이어의 트랜스퍼를 위해 D-sorbitol 용액을 첨가한 혼합된 PEDOT:PSS 잉크를 제조하여 PEDOT:PSS 박막과 실버 나노와이어 막이 강하게 접착하도록 하였다. 이 잉크를 이용하여 다양한 기판 상에 원하는 모양으로 PEDOT:PSS 박막을 잉크젯 프린팅하여 맞춤 제작의 PEDOT:PSS 트랜스퍼 매개체를 제작하였다. 두 번째로 스핀 코팅을 이용해 플라즈마 처리된 PDMS 스탬프 위에 매우 전도성이 높고 투명한 실버 나노와이어 막을 제작하였다. 마지막으로 PEDOT:PSS 박막이 형성된 기판과 실버 나노와이어가 코팅된 PDMS 스탬프가 하나로 접착된 샘플에 대하여 열 처리를 진행하여 실버 나노와이어의 선택적 트랜스퍼를 가능하게 하였고, 결과적으로 자유도가 높게 맞춤 제작이 가능한 실버 나노와이어가 트랜스퍼 된 PEDOT:PSS 전극을 제작하였다. 이 원리를 이용해 이 전극은 사용될 목적에 따라 다양한 기판 상에 제작되었으며, 우수한 전기광학적 특성을 가지고 있을 뿐만 아니라 수백 마이크로의 너비를 가지는 얇은 라인을 간단한 방법으로 형성할 수 있었다. 또한 실버 나노와이어 코팅 조건 조절을 통해 전극의 전기광학적 특성을 자유롭게 바꿀 수 있었고, 높은 표면 거칠기 및 하부 기판과의 약한 접착력과 같은 기존에 보고된 실버 나노와이어 막의 문제점들이 PEDOT:PSS 매트릭스 안에 부분적으로 임베딩된 실버 나노와이어의 구조에 의해 개선되었다. 플라스틱 기판 위 전극은 기존의 투명 전극으로 많이 사용되는 ITO에 비해 전기광학적 특성이 우수할 뿐만 아니라 기계적 특성 또한 우수하였다. 이러한 플렉시블 전극을 이용하여 LED 어레이 및 전 용액 공정의 폴리머 발광다이오드와 같은 맞춤 제작의 플렉시블 전자 소자로의 응용을 데모하였다. 특히 저전압에서 구동 가능한 폴리머 발광다이오드는 광학적 특성을 유지하면서 낮은 동작 전압을 보여 주었다.Abstract Contents List of Tables List of Figures Chapter 1. Introduction 1 1.1 Flexible display 1 1.2 Inkjet printing 4 1.3 Transfer printing 6 1.4 Organization of This Dissertation 9 Chapter 2. Uniformly coated PEDOT:PSS HIL on a hydrophobic EML for solution-processed inverted PLEDs 17 2.1 Indtroduction 17 2.2 Experiments 20 2.2.1 Fabrication of inverted PLEDs 20 2.2.2 Measurements 22 2.3 Results and discussion 23 2.3.1 Ethanol-dilution method for surface energy modulation 23 2.3.2 Spin-coated PEDOT:PSS HIL on EML 27 2.3.3 Characteristics of inverted PLEDs 30 2.4 Summary 34 Chapter 3. Transfer printing of conductive PEDOT:PSS for all solution-processed inverted PLEDs 42 3.1 Indtroduction 42 3.2 Experiments 45 3.2.1 Transfer printing of PEDOT:PSS electrodes 45 3.2.2 Fabrication of all solution-processed PLEDs 46 3.2.3 Characterizations and measurements 48 3.3 Results and discussion 50 3.3.1 Principles of transfer printing of PEDOT:PSS 50 3.3.2 Optoelectronic and mechanical properties 57 3.3.3 Characteristics of rigid p-PLEDs and a-PLEDs 60 3.3.4 Characteristics of flexible a-PLEDs 66 3.3.5 Highly customizable a-PLEDs including PMPLEDs 68 3.4 Summary 71 Chapter 4. A facile patterning of silver nanowire networks for low-voltage driven flexible electronics 78 4.1 Indtroduction 78 4.2 Experiments 82 4.2.1 Preparation of AgNW networks on a PDMS stamp 82 4.2.2 Preparation of inkjet-printed PEDOT:PSS 83 4.2.3 Selective transfer of AgNWs onto a transfer medium 84 4.2.4 Characterizations and measurements 85 4.2.5 Applications to flexible electronics 86 4.3 Results and discussion 87 4.3.1 Principles of AgNW-transferred PEDOT:PSS 87 4.3.2 Optoelectronic properties 92 4.3.3 Partially embedded AgNWs in the PEDOT:PSS matrix 95 4.3.4 Tunable optoelectronic properties 97 4.3.5 Fine patterning 99 4.3.6 Mechanical flexibility 101 4.3.7 Applications to flexible electronics 103 4.4 Summary 106 Chapter 5. Conclusion 115 Appendix 118 Publications and conferences 119 한글 초록 122Docto

Software Defined Applications in Cellular and Optical Networks

abstract: Small wireless cells have the potential to overcome bottlenecks in wireless access through the sharing of spectrum resources. A novel access backhaul network architecture based on a Smart Gateway (Sm-GW) between the small cell base stations, e.g., LTE eNBs, and the conventional backhaul gateways, e.g., LTE Servicing/Packet Gateways (S/P-GWs) has been introduced to address the bottleneck. The Sm-GW flexibly schedules uplink transmissions for the eNBs. Based on software defined networking (SDN) a management mechanism that allows multiple operator to flexibly inter-operate via multiple Sm-GWs with a multitude of small cells has been proposed. This dissertation also comprehensively survey the studies that examine the SDN paradigm in optical networks. Along with the PHY functional split improvements, the performance of Distributed Converged Cable Access Platform (DCCAP) in the cable architectures especially for the Remote-PHY and Remote-MACPHY nodes has been evaluated. In the PHY functional split, in addition to the re-use of infrastructure with a common FFT module for multiple technologies, a novel cross functional split interaction to cache the repetitive QAM symbols across time at the remote node to reduce the transmission rate requirement of the fronthaul link has been proposed.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201