Development of Gigabit Ethernet Optical Switched Access Network System Using Optical Packet Switches

In this paper the end-to-end TCP performance of a hybrid network composed of multiple Ethernet Passive Optical Networks (EPONs) in the access segment connected to the same edge node of a core network is evaluated. Three possible core network paradigms are considered: Optical Circuit Switching (OCS), Optical Burst Switching (OBS) and Optical Packet Switching (OPS). TCP performance is evaluated through simulations with ns-2. The hybrid network scalability is assessed by varying the number of EPONs connected to the same edge node and the number of Optical Network Units (ONUs) per EPON. Interoperability issues between access and core are investigated and the impact of the most important network parameters is highlighted. The three transfer modes considered for the core network are properly compared under different input conditions, discussing the related trade-offs that may lead to the most suitable choice based on the specific application scenario. Finally, some design issues are investigated with reference to emerging Long-Range EPON (LR-EPON) solutions.

Passive optical networks (PONs) have recently emerged to be a promising approach to enhance the penetration of fiber towards the subscriber side, thus further enables delivery of higher data-rate services to the subscribers. They feature easy network maintenance as there is no active component at the remote node (RN). However, in conventional PONs, both upstream and downstream bandwidths have to be time-shared among all optical network units (ONUs). By applying WDM technique to PONs, the total system capacity can be further enhanced. Each ONU enjoys a dedicated bandwidth and resolves the ranging problem as in PONs. In both conventional PON and WDM-PON, little work has been done to offer protection capability though fiber fault detection methods have been extensively studied. We propose a novel network architecture for WDM-PON which offers 1:1 protection capability. In case of any fiber cut between remote node and ONUs, the affected ONU can re-route the wavelength channels via the adjacent ONU and can still maintain normal bidirectional traffic.

In this PhD dissertation multi-rate models are examined for the performance analysis of telecommunication networks through mathematical analysis and simulation. Particular emphasis is given to optical networks. The main goal is the development of analytical models for the calculation of network performance metrics, such as blocking probabilities, transmission delay and utilization of the common channel. The proposed analytical models are distinguished according to the network technologies. Three different technologies are considered: A) Wavelength routed optical networks. B) Optical access networks. C) Wireless Internet access networks. Multi-rate loss models are proposed for the performance evaluation of wavelength routed optical networks. Firstly, the case of a single link is considered and then a mesh all-optical network is examined. In addition, analytical models are proposed for Optical Packet Switching (OPS) networks, for the case of an all-optical OPS switch and of an OPS mesh network. Multi-rate analytical models are proposed for the evaluation of the performance of Passive Optical Networks (PONs) implementing different multiple access methods. For the case of Time Division Multiple Access (TDMA) the Ethernet PON is studied, which supports multiple service-classes. Regarding the Wavelength Division Multiplexing (WDM) PONs a hybrid WDM-TDMA PON is considered and the call-level performance is evaluated. Calls are distinguished by their arrival process, which can be random or quasi random, by their bandwidth requirements, which can be fixed of elastic and by their behavior during their service, which can be calls of fixed transmission rate or calls that alternate between ON and OFF periods. Finally multi-rate loss models are proposed for the case of Optical Code Division Multiple Access (OCDMA) PONs that take into account the user activity and the presence of additive noise in the transmission channel. For the performance analysis of wireless Internet access networks analytical models are proposed, which implement the IEEE 802.11 protocol or the IEEE 802.11e protocol. The proposed analysis calculated the saturation throughput and the end-to-end packet delay as a function of the Medium Access Control (MAC) delay and the queueing delay. In all cases the accuracy of the proposed models is validated through simulation.

Simultaneous upstream and inter optical network unit communication for long reach PON using single transmitter and self-phase modulation

The wide deployment of wavelength-division multiplexing technology and new transmission techniques have resulted in significant increases in the transmission capacity in optical fibers, both in the number of wavelengths and the bandwidth of each wavelength channel. Meanwhile, the fast growth of the Internet demands more data switching capacity in the network in order to deliver high bandwidth to end users. Although the capacity of electronic routers has been increasing consistently in the past, optical switching appears to be a more cost-effective way to switch individual wavelengths. As the bit rate per wavelength channel continues to grow, optical subwavelength switching emerges as a new paradigm capable of dynamically delivering the vast bandwidth WDM offers. This article discusses one of such techniques, namely optical packet switching, and its performance perceived by end users in optical mesh networks. Specifically, our investigation reveals the benefit of using electrical ingress buffering and traffic aggregation to reduce packet-loss rate of optical packet-switched networks. Through simulation experiments, we present an evaluation of the network's TCP-level performance based on the proposed architecture.

We develop an integrated optical packet and circuit switching node in which signaling via optical packet switching is implemented. We demonstrate 80 (8λ × 10) Gbit/s optical packet switching with <;1E-4 packet-loss-rate, 8-lightpaths establishment, and dynamic wavelength-resources control.

The huge traffic growth which is currently experienced (traffic nearly doubles every year) and foreseen to continue for several years calls for high capacity networks capable of efficiently handling various types of traffic (voice, video, data). WDM (Wavelength Division Multiplexing) optical networks exploiting also fast optical packet switching are expected to provide the required capacity and flexibility for the next generation of high-speed networks. In this context, the European ACTS KEOPS project (KEys to Optical Packet Switching) has concentrated on the definition, development and assessment of optical packet switching and routing networks capable of providing transparency to the payload bit rate. Optical packets of fixed duration have been considered where the payload bit rate, which is user-dependent, can vary from a few hundred Mb/s to 10 Gb/s whereas the header is at a fixed low bit rate (622 Mb/s) to facilitate processing at the network/node interfaces. The challenge addressed by the KEOPS project was therefore to combine the advantages of the relatively coarse-grained WDM techniques with emerging all-optical switching capabilities to yield a high-throughput optical platform directly underpinning next generation data networks (ATM, IP). The project which involved nine partners (Alcatel Alsthom Recherche (F), France Telecom-CNET (F), CSELT (I), Technical University of Denmark (DK), Alcatel CIT (F), Alcatel SEL (D), University of Bologna (I), ETH-Zurich (CH) and University of Strathclyde (UK)) has addressed both network and system studies as well as demonstration experiments based on advanced optoelectronic components developed in the project in order to validate the proposed concept.

Statistical multiplexing at the optical layer has been considered a critical requirement in order to build the next generation of ultra-high capacity optical transport networks in a cost-efficient manner. However, even today, the state of the art of commercially available optical core networks is based on mature wavelength switching and routing technologies, which lack a transport and control plane architecture that can support statistical traffic multiplexing with guaranteed Quality of Service (QoS) across a wide range of QoS parameters even if they can support fast reconfiguration at msec time scales. For several years, most research efforts have focused on the concepts of Optical Burst Switching (OBS) and Optical Packet Switching (OPS), which are based on the hybrid use of electronic nodes and optical switches to exploit Time Division Multiplexing (TDM) in order to achieve statistical multiplexing and dynamic resource reservation over optical networks. While burst switching has been experimentally proven as a technically feasible technique, its performance suffers especially under strict requirements for QoS guarantees. In this paper we evaluate the performance gains that can be achieved exploiting statistical multiplexing over a large scale core optical network and we demonstrate the efficiency of the CANON architecture (Clustered Architecture for Nodes in an Optical Network) as a viable alternative to OBS, which can achieve both targets for statistical multiplexing gains and QoS guarantees at the same time.

This paper presents the design architecture of a new optical switching device named Protection Switching Device (PSD) for providing protection and restoration against fiber failures/faults in the distribution region of passive optical network (PON). The developed PSD prototypes are employed at the customer end, just before the optical network units (ONUs) to ensure the data flow continuously due to breakdown occur in the network and instantly repair operation. The network is protected from fiber/equipment failures by using optical switches to bridge the optical signals and dual feed them on diversely routed working line and protection line or neighbor line. When the failure is detected, the protection mechanism will be activated and divert the optical signal direction to the protection line or neighbor line according to the types of failure condition and location of failures in PON.

Optical packet switching (OPS) is being considered as one of the switching technologies for a future optical internet. For contention resolution in an optical packet switching (OPS) system, the wavelength dimension is generally used in combination with a fibre delay line (FDL) buffer. In this study, the authors propose to reduce the number of tunable wavelength converters (TWCs) by sharing TWCs for cost-effective design of an asynchronous OPS system with a shared or an output FDL buffer. Asynchronous and variable-length packets are considered in the OPS system design. To investigate the number of TWCs needed for the OPS system, an algorithm is proposed, which searches for an available TWC and an unused internal wavelength, as well as an outgoing channel. This algorithm is applied to an OPS system with a shared or an output FDL buffer. Also, the number of internal wavelengths (i.e. the conversion range of the TWC) needed for an asynchronous OPS system is presented for cost reduction of the OPS system.

Energy-efficient passive optical networks (PONs) have gained significant interest since they are estimated to be the largest energy consumers among the wired access networks for the next ten years. In Ethernet PONs (EPONs), the equipment placed at the customer premises, i.e., the optical network units (ONUs), has been shown to be responsible for almost 65% of the total EPON power consumption. Sleep mechanisms, implemented at ONUs’ side, can contribute to the EPONs’ energy-efficiency. However, the tradeoff between energy saving and quality of service (QoS) requirements should be carefully tuned, especially when the downstream transmission is considered, to achieve the desirable results. In this paper, we propose a general framework that exploits formal methods as an approach for EPONs’ energy-efficiency. The idea is to build a holistic model representing both the state machine of the ONU in its details as well as the ONU’s communication with the optical line terminal under EPONs’ specifications. Verification results reveal that, guided by the QoS constraints and considering the transitions’ cost, an “aggressive” policy defining long sleep periods of the 100 ms order can be up to 24.9% beneficial for energy-efficiency compared to a “conservative” policy with sleep periods of the 10 ms order.

Modeling and performance analysis of a data center network (DCN) combining optical packet switching (OPS) and agile optical circuit switching (OCS) in a unified platform are presented. Hybrid optoelectronic packet routers which combine optical switching fabric and electronic buffers are used, supporting 100 Gbit/s (25 Gbit/s × 4 wavelengths) optical packets. OCS transmission is implemented by a novel “express path,” (ExP) an instant wavelength path on demand, which enables certain flows following the ExP with no packet contention, whereas ordinary OPS packets are switched with a deflection routing algorithm and buffering for contention resolution. This architecture can support OCS for large and reliability-sensitive data transferring and OPS for latency-sensitive applications. The performance of the network is investigated via numerical simulations of top-of-rack switch (ToR)-to-ToR traffic in an N-dimensional (up to 4096 node) torus topology. We have made the following observations: 1) torus topology results in high throughput and can be scaled out by increasing the dimension; 2) contention resolution between OPS and agile OCS is needed and our proposed strategies enhance the overall performance; and 3) in a lightly to moderately loaded case of OPS traffic, more than 100 ExPs can be supported simultaneously with acceptable affect on OPS.

We present for the first time remote powering of a 3-D MEMS for optical switching using light over fibre. The low power switch with integrated optical splitters is suitable at non-powered remote PON distribution sites. Introduction The rapid deployment of fibre-to-the-home (FTTH) poses a number of new operational challenges in managing fibre due to the growing outside fibre plant infrastructure and the inherent churn in access networks [1]. Automating fibre management using remotely controlled optical switches has been proposed to efficiently manage subscriber connectivity and fault localization without human intervention, and to reduce the number of network and test equipment [2]. Early field trials have confirmed the benefits to operate and maintain fibrebased networks [3]. The deployment of switches in Central Offices (CO) for FTTH point-to-point networks is relatively simple. The insertion of optical switches, however, in Passive Optical Networks (PON) at Fibre Distribution Hub (FDH) sites in the field is much more difficult because those sites are usually not powered. We demonstrate in this paper a remotely powered fibre management solution using a low-power 3DMEMS optical switch and a light-over-fibre powering technique. We also report improved environmental performance for field switch operation. Integrated PON 3-D MEMS Switch Fig.1 shows a typical FDH layout in a PON: a first bay with optical splitters is connected to the Optical Line Terminal (OLT) at the CO; a second bay with fibre terminations is connected to residential homes. Optical splitters Patch-cords OLT ONU CO Homes Outside Plant Truck-rolls for patching Field OTDR measurements ONU FDH Fig. 1. PON FDH with discrete splitters and manual fibre management requiring technician dispatch to connect subscriber to OLT or test fibres with OTDR. Each time a subscriber is added, a technician must be dispatched at the FDH site to connect it to an unused OLT port. If subscribers are connected up-front, additional OLTs are required due to limited market penetration, thus increasing greatly the initial investment cost per paying subscribe. Technicians also go in the field to perform OTDR measurements to certify fibre installation or to trouble-shoot faults. All those costly and error-prone human interventions can be alleviated by the insertion of an optical switch at the FDH sites (Fig.2). The software-controlled switch connects a subscriber to the desired splitter port, packing subscribers onto the minimum number of OLTs in real time. All the home run fibres can be checked using a test fibre connected to an OTDR at the CO that can be shared among multiple FDH sites. Optical switch with splitters OLT ONU CO Outside Plant

Mode-division-multiplexing technology is highly attractive to increase the capacity of optical interconnects. Various multimode operations have been investigated, among which optical mode switches provide one of the most important functions in mode-division-multiplexing systems. However, current optical mode switches have a non-negligible switching time, which can lead to an undesired cumulative delay in the optical network. In this contribution, we propose and experimentally demonstrate an optical mode switch using a three-waveguide-coupling structure in the lithium niobate on insulator platform. The demonstrated optical mode switch has an insertion loss of 4.3 dB, an extinction ratio of 17.1 dB, and a switching time of below 28 ps. This work paves the way for future chip-scale high-speed mode-division-multiplexing systems.

Adopting the pay-as-you-grow approach to upgrade passive optical network (PON) facilities by WDM technology insures the smoothness of the upgrade, and also results in the coexistence of wavelength-fixed/tunable optical network units (ONUs) in WDM/TDM PONs. Dynamic bandwidth allocation (DBA) is the key to support such coexistence of heterogeneous ONUs. Thus, DBA is also the key to support the smooth evolution of PONs. To more fairly coordinate the bandwidth allocation among the coexisting heterogeneous ONUs, a differentiated grant sizing (DGS) scheme is proposed. In DGS, not only the fairness between the wavelength-fixed/tunable ONUs but also the fairness between the lightly/heavily loaded ONUs is taken into account. To further carry out load balancing among wavelengths, a grant scheduling scheme is also proposed to cooperate with the grant sizing scheme. In the grant scheduling scheme, a measure of the ONUs’ flexibility is given, and then the least flexible job first rule (LFJF) is adopted for joint wavelength and time-slot assignment. Finally, to demonstrate the effectiveness of the proposed algorithm, a series of comparative analyses is conducted based on simulation experiments.