Shing-Wa Wong

Sleep Mode for Energy Saving PONs: Advantages and Drawbacks

A common approach to reduce energy consumption in communication networks is to allow network elements to switch to sleep mode. While this technique has been widely utilized in wireless networks, recent studies have proposed to exploit sleep mode in wired networks to conserve energy as well. This paper focuses on some feasible implementations of sleep mode in passive optical networks (PONs). In particular, ONU sleep mode is considered. The paper first outlines the ONU wake-up process using current time division multiplexing (TDM) PON protocols. Current and novel optical network unit (ONU) architectures that selectively switch-off some elements are then described. Their advantages in terms of energy savings are analytically computed under different traffic scenarios. Using the proposed architectures, analytical results show more than 50% energy saving under realistic TDM traffic. Finally, possible drawbacks in terms of new scheduling challenges are also discussed and potential solutions are presented.

Hybrid Architecture and Integrated Routing in a Scalable Optical–Wireless Access Network

We propose a hybrid optical-wireless access network that consists of reconfigurable optical backhaul and wireless mesh networks (WMNs). The complementary characteristics of wireless and optical networks are combined to provide a broadband and ubiquitous last-mile connection. Wireless mesh routers are deployed to penetrate the vicinity of end users for a flexible and ubiquitous connection. It eliminates massive and geographically scattered deployment of physical infrastructure to reach the end users. The broadband optical backhaul consists of optical ring and multiple tree networks, connecting the central hub and WMNs. The ends of the optical tree networks connect to the wireless gateway routers of WMNs. A hybrid time-division-multiplexing (TDM)/wavelength-division-multiplexing (WDM) optical backhaul is realized by wavelength-multiplexing multiple TDM-passive-optical-network streams. This hybrid architecture provides graceful scalability, cost effectiveness, and bandwidth efficiency. To adapt to a change of the overall demand in different districts, reconfigurability is implemented in the optical backhaul utilizing tunable optical transceivers. An experimental test bed is implemented to evaluate the reconfigurable scheme. Given the synergy of the optical backhaul and WMNs, we propose an integrated-routing algorithm to achieve load balancing on this hybrid architecture. The simulation using NS2 shows an approximately 25% throughput improvement with load balancing.

Energy efficiency in passive optical networks: where, when, and how?

This article provides an overview of current efforts in reducing energy consumption in passive optical access networks. Both ITU-T and IEEE standardized PONs are considered. The current solutions proposed by standardization authorities, industry, and academia are classified based on the layer they address in the standardized architectures: physical layer, data link layer, and hybrid. Then, the article provides answers to major questions, such as where, when, and how to reduce PON energy consumption in TDM PONs by means of a quantitative evaluation. Results show that to reduce energy consumption, ONUs must be provided with physical devices that are not only power-efficient but also provide improved services (e.g., fast synchronization) to upper layers. For this latter purpose, novel physical ONU architectures are proposed to speed up the synchronization process and enable effective data link layer solutions. Finally, the feasibility of switching ONUs to low power mode in idle slots is assessed through a testbed implementation.

Experimental Validation of an Access Evolution Strategy: Smooth FTTP Service Migration Path

We examine a cost-effective upgrade path using WDM over deployed FTTP infrastructures with capability to co-exist with a working G-PON system. We demonstrate overlay of five Gigabit signals operating between 1531nm~1611lnm over a working G-PON.

Distributed MIMO antenna architecture for wireless-over-fiber backhaul with multicarrier optical phase modulation

A novel optical phase-modulated wireless-over-fiber backhaul architecture for next generation cellular network is presented and experimentally demonstrated for high capacity wireless multicarrier uplink transmission on a single wavelength.

Photonic components for future fiber access networks

Fiber based access networks are recognized as promising technologies for solving broadband bandwidth bottlenecks. TDM-PONs, which are passive and non-reconfigurable, are the most widely deployed type of fiber access networks today. However, due to their passive nature, TDM-PONs encounter several issues such as inflexible coverage, lack of intelligence for control, and inability to counter security attacks. Based on current issues in optical access networks, we propose a novel non-volatile, reconfiguration node. The proposed remote node can reconfigure the network to adapt to varying degrees of deployment conditions and/or network attacks. Moreover, the proposed remote node incorporates a novel quasi-passive device that reconfigures using remotely supplied energy from CO. This quasi-passive device technology does not consume any energy once it reconfigures into a new latching states. Therefore, the proposed remote node has very low energy consumption and does not require local power supply to preserve the passivity of the passive distribution network. In particular, the proposed quasi-passive device technology is implemented using a novel tri-state Micro- Electro-Mechanical System (MEMS) actuator structure and the device demonstrates very small energy consumption requirement to enable energy be remotely supplied from CO. Also, the MEMS structure is shown to demonstrate acceptable insertion losses to makes it suitable for flexible energy distribution. Simulation study shows the proposed reconfigurable device would outperform traditional passive splitter in terms of maximum number of supportable users under realistic deployment conditions.

OPN01-6: Enabling Security Countermeasure and Service Restoration in Passive Optical Networks

In this paper, we introduce a novel passive and wavelength selective remote node specifically designed to enable security countermeasure in PONs. The central office could physically isolate problem makers from the network without disrupting regular links by issuing a wavelength specific control signal to this device. With its wavelength selective nature, the countermeasure-enabled passive device is also a natural candidate to a WDM-PON remote node. To demonstrate its feasibility, a discrete version of the device is implemented. In addition to enable countermeasure capability, a new kind of PON restoration technique that employs a hybrid optical-wireless network is proposed. Finally, cost and performance considerations are discussed in an 8-channel planer lightwave circuit example.

MARIN Hybrid Optical-Wireless Access Network

A novel hybrid optical-wireless access network is proposed for metropolitan area. This novel architecture consists of wireless mesh networks and a reconfigurable optical backhaul and aggregation network based on TDM-PON technology.

Reconfigurable Optical Backhaul and Integrated Routing Algorithm for Load Balancing in Hybrid Optical-Wireless Access Networks

Various wireless and optical access technologies have been developed to address different issues in access networks. By combining the complementary characteristics of wireless and optical networks, a hybrid optical-wireless access network will enable broadband, ubiquitous, and cost-effective last-mile service to the users. In this paper, a reconfigurable optical backhaul leveraging both the standard Time Division Multiplexing Passive Optical Network (TDM-PON) technology and wavelength division multiplexed (WDM) ring is proposed to achieve a higher bandwidth efficiency than simply using point-to-point backhaul links. Furthermore, an integrated routing algorithm which can adapt to the change of overall demand among different service districts by taking advantage of the proposed optical backhaul is also proposed. An experimental testbed is implemented to evaluate the reconfigurable scheme and its feasibility. Also, simulation results show that the proposed integrated routing with load balancing can improve the performance in hybrid optical and wireless networks.

OPN03-2: MARIN: Metro-Access Ring Integrated Network

We propose a novel metro-access integrated network that integrates hybrid TDM/WDM optical access networks into MAN, such that the capacity upgrade in both networks can be achieved simultaneously. By interconnecting multiple access ring networks, MARIN provides alternative paths for MAN traffic to be routed on it with high aggregated throughput. Thus it enables the deployed infrastructure, installed hardware, and available bandwidth of the optical access networks to be shared and leveraged by MAN. Cyclic wavelength selective switch, fast tunable laser, and optical parametric wavelength conversion are used in MARIN system for network reconfigurability, resource sharing in the central office, and wavelength set conversion, respectively. The key components are demonstrated with experimental testbed and their performance is evaluated.