Herein we report on the fabrication and the properties of two highly efficient blue light emitting multilayer polymer light emitting diodes (PLEDs). The first device structure combines a thermally stabilized polymer with a material processed from an orthogonal solvent, allowing for the fabrication of a triple layer structure from solution. The well known poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), which can be stabilized in a bake-out procedure, was used as a hole transporting layer. A novel pyrene – triphenylamine (PPyrTPA) copolymer was used as emissive layer. The stack was finalized by a poly(fluorene) - derivative with polar side-chains, therefore being soluble in a polar solvent which allows for the deposition onto PPyrTPA without redissolving. The resulting PLED showed bright-blue electroluminescence (CIE1931 coordinates x=0.163; y=0.216) with a high efficiency of 1.42 cd/A and a peak luminescence of 16500 cd/m². The second presented device configuration comprises a thermally stabilized indenofluorene – triphenylamine copolymer acting as hole transporter, and an emissive copolymer with building blocks specifically designed for blue light emission, effective charge carrier injection and transport as well as for exciton generation. This multilayer PLED led to deep-blue emission (CIE1931 x=0.144; y=0.129) with a remarkably high device efficiency of 9.7 cd/A. Additionally, atomic force microscopy was carried out to investigate the film morphology of the components of the stack and x-ray photoemission spectroscopy was performed to ensure a full coverage of the materials on top of each other. Ultraviolet photoemission spectroscopy confirmed the desired type-II band level offsets on the individual interfaces.
KEYWORDS: Network architectures, Switching, Broadband telecommunications, Data storage, Optical networks, Switches, Multimedia, Computer architecture, Local area networks, Video
The suitability and efficiency of network architectures strongly depend on the service requirements and the mixture of services at different network levels. A case study has been performed in which five different service scenarios have been defined considering the characteristics of network operators. Starting with a service scenario which assumes only Layer 3 IP services, the amount of Layer 2 (Ethernet) and Layer 2 services (leased line) have been increased subsequently in the remaining four scenarios. Moreover, Layer 1 services have been differentiated with respect to broadband leased lines and narrowband services. The service scenarios have been applied to assess network architectures based on IP/MPLS, Ethernet and flexible and static optical systems, respectively. The impact of control plane implementations, i.e GMPLS and ASON, have been analyzed. Ethernet is making its way into metro and core networks. The development of Ethernet services and technology and their integration into MPLS/GMPLS based networks is still hampered by open issues. Evolutions in this area will be a key differentiator for network architecture evolutions.
The paper addresses the migration path and trade-offs involved in the evolution towards intelligent optical networks that allow scalable and flexible transport of a range of client formats and services. Disruptive all-optical switching and ultra-long reach WDM transmission technologies enable all-optical networks without opto-electronic conversion along paths that can span thousands of kilometers. Optical transport networks coupled with advances in distributed routing and signaling mechanisms are enabling the deployment of Automatically Switched Optical Networks (ASON). The paper discusses in detail the network architecture, optical switching capability, and network management and control architecture involved in the migration from existing and widely deployed WDM optical point-to-point systems to ASONs. The paper reports the findings of the Global Seamless Network (GSN) demonstrator at Deutsche Telekom, in which the concepts of intelligent optical transport networks are being demonstrated and evaluated. Further, a special emphasis is devoted to the question of managing survivability in ASONs. Simulation results comparing different approaches are presented, which illustrate the trade-off between dimensioning and performance of resilience mechanisms. The multi-layer integration between optical and higher layers is addressed from both a control plane and survivability perspective. Scenarios with different clients of the optical layer such as SDH and IP/MPLS are analyzed.
Today, Wavelength Division Multiplexing (WDM) transmission systems are deployed extensively in transport networks. They are used mainly for static point-to-point connections. With the availability of fast reconfigurable Optical Cross Connects (OXC) and the introduction of a control plane in the Optical Transport Network (OTN), optical channel based logical networks can be built for dynamic WDM networks.
Resilience in current transport networks is mainly based on static SONET/SDH dedicated and shared protection. Distributed control planes allow new, flexible protection mechanisms (e.g. GMPLS reroute and fast reroute).
To evaluate future distributed control concepts and new resilience schemes in transport networks, we have implemented a dynamic OTN simulation model.
Several case studies have been performed using different protection and restoration methods. Different failure scenarios (single or multiple link failures) were used. The paper evaluates the case studies in terms of scalability, recovery time criteria, capacity use (efficiency) and availability. It is shown that the new and flexible resilience schemes are a promising alternative to traditional statically preplanned protection in transport networks. Furthermore, they provide increased network availability in multiple failure cases.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.