Dynamically reconfigurable optical access network

This dissertation presents the research results on a fiber-optic high-bitrate access network which enables dynamic bandwidth allocation as a response to varying subscribers' demands and bandwidth needs of emerging services. The motivation of the research is given in Chapter 1 "Introduction" together with a brief comparative discussion on currently available and future access networks. The idea of wavelength reconfigurability in the last-mile networks is described as a solution for more efficient bandwidth utilization and a subject of the Broadband Photonics project. Chapter 2 "Wavelength-flexible WDM/TDM access network - architecture" provides a comprehensive description of the proposed solution with each network element being analyzed in terms of its functionalities. This includes a colorless optical network unit and a reconfigurable optical add/drop multiplexer. An estimation of power budget is followed by the choice of wavelength set and network control and management layer overview. In Chapter 3 "Reflective transceiver module for ONU" after discussing different communication schemes and modulation formats three approaches to a colorless high-bitrate transmitter are analyzed in detail. This includes experiment and simulation results on a reflective semiconductor optical amplifier, reflective electro-absorption modulator and a Michelson-interferometer modulator. The Chapter is concluded with a comparative discussion. Chapter 4 "Reconfigurable optical add/drop multiplexer" discusses another key element in the proposed network architecture which is an integrated structure of micro-ring resonators providing wavelength reconfigurability. The measured characteristics assess the applicability of the device able to support unicast and multicast transmission. A range of possible sources of signal degradation in the access links are analyzed in Chapter 5 "Transmission and network impairments in the access network". An estimation of potential power penalties resulting from such impairments in the proposed system follow afterwards. Special attention is paid to optical in-band crosstalk penalties and improvement methods in Chapter 6 "Interferometric crosstalk in the access network with an RSOA". This subject is treated extensively with the support of mathematical considerations and experimental results. Proof-of-concept experiments of the proposed network architecture are presented in Chapter 7 "Reconfigurable WDM/TDM access network - experiments". The results of bidirectional transmission of high-bitrate WDM signals in different wavelength allocation schemes are discussed in detail. From there, by means of simulations the behavior of a full-scale network is assessed. In Chapter 8 "Migration towards WDM/TDM access network" the migration scenario from currently deployed fiber-optic access networks towards the novel solution is proposed. Afterwards, a short dispute on the economics of last-mile fiber technologies is included. Finally, the work is concluded and potential future research ideas based on this thesis are given in Chapter 9 "Conclusions and further work"

Dynamically reconfigurable optical access network

This dissertation presents the research results on a fiber-optic high-bitrate access network which enables dynamic bandwidth allocation as a response to varying subscribers' demands and bandwidth needs of emerging services. The motivation of the research is given in Chapter 1 "Introduction" together with a brief comparative discussion on currently available and future access networks. The idea of wavelength reconfigurability in the last-mile networks is described as a solution for more efficient bandwidth utilization and a subject of the Broadband Photonics project. Chapter 2 "Wavelength-flexible WDM/TDM access network - architecture" provides a comprehensive description of the proposed solution with each network element being analyzed in terms of its functionalities. This includes a colorless optical network unit and a reconfigurable optical add/drop multiplexer. An estimation of power budget is followed by the choice of wavelength set and network control and management layer overview. In Chapter 3 "Reflective transceiver module for ONU" after discussing different communication schemes and modulation formats three approaches to a colorless high-bitrate transmitter are analyzed in detail. This includes experiment and simulation results on a reflective semiconductor optical amplifier, reflective electro-absorption modulator and a Michelson-interferometer modulator. The Chapter is concluded with a comparative discussion. Chapter 4 "Reconfigurable optical add/drop multiplexer" discusses another key element in the proposed network architecture which is an integrated structure of micro-ring resonators providing wavelength reconfigurability. The measured characteristics assess the applicability of the device able to support unicast and multicast transmission. A range of possible sources of signal degradation in the access links are analyzed in Chapter 5 "Transmission and network impairments in the access network". An estimation of potential power penalties resulting from such impairments in the proposed system follow afterwards. Special attention is paid to optical in-band crosstalk penalties and improvement methods in Chapter 6 "Interferometric crosstalk in the access network with an RSOA". This subject is treated extensively with the support of mathematical considerations and experimental results. Proof-of-concept experiments of the proposed network architecture are presented in Chapter 7 "Reconfigurable WDM/TDM access network - experiments". The results of bidirectional transmission of high-bitrate WDM signals in different wavelength allocation schemes are discussed in detail. From there, by means of simulations the behavior of a full-scale network is assessed. In Chapter 8 "Migration towards WDM/TDM access network" the migration scenario from currently deployed fiber-optic access networks towards the novel solution is proposed. Afterwards, a short dispute on the economics of last-mile fiber technologies is included. Finally, the work is concluded and potential future research ideas based on this thesis are given in Chapter 9 "Conclusions and further work"

PON-Based Connectivity for Fog Computing

Fog computing plays a crucial role in satisfying the requirements of delay-sensitive applications such as connected vehicles, smart grids, and actuator networks by moving data processing close to end users. Passive optical networks (PONs) are widely used in access networks to reduce the power consumption while providing high bandwidth to end users under flexible designs. Typically, distributed fog computing units in access networks have limited processing and storage capacities that can be under or over utilized depending on instantaneous demands. To extend the available capacity in access network, this paper proposes a fog computing architecture based on SDN-enabled PONs to achieve full connectivity among distributed fog computing servers. The power consumption results show that this architecture can achieve up to about 80% power savings in comparison to legacy fog computing based on spine and leaf data centers with the same number of servers

A Resilient AWGR and Server Based PON Data Centre Architecture

This paper studies the resilience of an AWGR and server based PON DCN architecture against link failure scenarios and proposes a modified design for improved resilience. A MILP model is developed to evaluate the performance of the modified design considering different failure scenarios. The results show a limited increase in power consumption and a large increase in delay under failure scenarios compared to the normal state