Dynamically reconfigurable long-reach PONs for high capacity access

Fibre-to-the-Premises (FTTP) is currently seen as the ultimate in high-speed transmission technologies for delivering ubiquitous bandwidth to customers. However, as the deployment of network infrastructure requires a substantial investment, the main obstacle to fibre deployment is that of financial viability. With this in mind, a logical strategy to offset network costs is to optimise the infrastructure in order to capture a greater amount of customers over larger areas with increased sharing of network resources. This approach prompted the design of a long-reach passive optical network (LR-PON) in which the physical reach and split of a conventional PON is significantly increased through the use of intermediate optical amplification. In particular, the LR-PON architecture effectively integrates the metro and access networks enabling the majority of local exchange sites to be bypassed resulting in a substantial reduction in field equipment requirements and power consumption. Furthermore, the extension in physical reach and split can be coupled with an increased information capacity through the use of time- and wavelength division multiplexing (TWDM) which serve to exploit the large bandwidth capabilities offered by single-mode fibre. In this project, reconfigurable TWDM LR-PON architectures which dynamically exploit the wavelength domain are proposed, assembled and characterised in order to establish an economically viable ‘open access’ environment that is capable of concurrently supporting multiple operators offering converged services (residential, business and mobile) to support diverse customer requirements and locations. The main investigations in this work address the key physical layer challenges within such wavelength-agile networks. In particular, a range of experimental analysis has been carried out in order to realise the critical component technologies which include low-cost, 10G-capable, wavelength-tuneable transmitters for mass-market residential deployment and the development of gain-stabilised optical amplifier nodes to support the targeted physical reach (≥ 100km) and split (≥ 512). Finally, the feasibility of the proposed dynamically reconfigurable LR-PON configurations as a flexible and cost-effective solution for future access networks is verified through full-scale network demonstrations using an experimental laboratory test-bed

Performance analysis and centralised optical processing in next generation access networks

The Next Generation Passive Optical Network (NG-PON) is currently being standardised and developed, with a goal to achieve higher bandwidth at 10Gb/s, greater capacity at thousands of users and longer backhaul reach at 60km or 100km. The aim is to provide cost effective solutions for telecom operators to vastly deploy optical access networks, enabling customers with the benefit of the greater bandwidth and wider range of services. This thesis presents research that has identified and addressed various design issues relating to next generation access networks. Interferometric noise may be present in future, ring based, access networks which utilise WDM and OADMs. Simulation and experiment results are presented which studies the performance tolerance to not-precisely-defined wavelength, in the presence of interferometric noise. The impact of receiver electrical filtering was also investigated. The next generation access network will, in the upstream direction, use burst transmission and are likely to need a large tolerance to wavelength drift due to the low cost equipment used at the customer’s premises. A demonstration of optical burst equalisation was presented, based on SOAs. This study also explores the possibility of reducing the SOA saturation induced non-linear distortions through simulations and experiments. As an extension to the optical burst equaliser and to remedy the saturation induced distortions, an intermediate site optical processing system was proposed. This solution not only performs burst-mode wavelength conversion at 10 Gb/s, but also pre-chirps the signal to allow long-reach transmission and suppressed level fluctuation to ease the requirements on the burst-mode receiver. As a result, a proof of concept 10Gb/s Wavelength Converting Optical Access Network (WCOAN) with up to 62km DWDM backhaul is experimentally demonstrate. It is designed to consolidate drifting wavelengths, generated with an uncooled laser in the upstream direction, into a stable wavelength channel for DWDM long backhaul transmission

Wavelength reconfigurability for next generation optical access networks

Next generation optical access networks should not only increase the capacity but also be able to redistribute the capacity on the fly in order to manage larger variations in traffic patterns. Wavelength reconfigurability is the instrument to enable such capability of network-wide bandwidth redistribution since it allows dynamic sharing of both wavelengths and timeslots in WDM-TDM optical access networks. However, reconfigurability typically requires tunable lasers and tunable filters at the user side, resulting in cost-prohibitive optical network units (ONU). In this dissertation, I propose a novel concept named cyclic-linked flexibility to address the cost-prohibitive problem. By using the cyclic-linked flexibility, the ONU needs to switch only within a subset of two pre-planned wavelengths, however, the cyclic-linked structure of wavelengths allows free bandwidth to be shifted to any wavelength by a rearrangement process. Rearrangement algorithm are developed to demonstrate that the cyclic-linked flexibility performs close to the fully flexible network in terms of blocking probability, packet delay, and packet loss. Furthermore, the evaluation shows that the rearrangement process has a minimum impact to in-service ONUs. To realize the cyclic-linked flexibility, a family of four physical architectures is proposed. PRO-Access architecture is suitable for new deployments and disruptive upgrades in which the network reach is not longer than 20 km. WCL-Access architecture is suitable for metro-access merger with the reach up to 100 km. PSB-Access architecture is suitable to implement directly on power-splitter-based PON deployments, which allows coexistence with current technologies. The cyclically-linked protection architecture can be used with current and future PON standards when network protection is required

Voyager spacecraft system. Preliminary design, volume B /book 3 of 3/ - Alternate designs considered - G and C, Pwr, C and S, prop, plans

Alternate designs for guidance and control, power, controller and sequencer systems for Voyager spacecraft - effect of alternate designs on schedule and implementatio

Research reports: 1985 NASA/ASEE Summer Faculty Fellowship Program

A compilation of 40 technical reports on research conducted by participants in the 1985 NASA/ASEE Summer Faculty Fellowship Program at Marshall Space Flight Center (MSFC) is given. Weibull density functions, reliability analysis, directional solidification, space stations, jet stream, fracture mechanics, composite materials, orbital maneuvering vehicles, stellar winds and gamma ray bursts are among the topics discussed