Akira Misawa

WDM knockout switch with multi-output-port wavelength-channel selectors

This paper proposes the photonic knockout switch that uses wavelength division multiplexing (WDM). The proposed switch uses two types of WDM switching: broadcast-and-select (B and S) switching and wavelength routing. To extend the size of the knockout switch concentrator, a multi-output-port wavelength-channel selector is used, which enables us to reduce the number of optical gates and wavelength routers. Simple and distributed contention control becomes possible in the optical domain through the use of the wavelength-routing switch. In this switch, coherent crosstalk is a serious problem. We measured the bit error rates of a four-output-port wavelength-channel selector. The power penalty due to the presence of coherent crosstalk is less than 1 dB.

A prototype broadcast-and-select photonic ATM switch with a WDM output buffer

A rack-mounted prototype of a broadcast-and-select (B and S) photonic ATM switch is fabricated. This switch has an optical output buffer utilizing wavelength division multiplexed (WDM) signals. The WDM technology solves. The cell-collision problem in a broadcast-and-select network and leads to a simple network architecture and the broadcast/multicast function. The prototype can handle 10-Gb/s nonreturn-to-zero (NRZ) coded cells and 5-Gb/s Manchester-coded cells and has a switch size of four. In this prototype, the level and timing design are key issues. Cell-by-cell level fluctuation is overcome by minimizing the loss difference between the optical paths and adopting a differential receiver capable of auto-thresholding. The temperature control of delay lines was successful in maintaining the phase synchronization. Using these techniques, we are able to provide a WDM highway with a bit error rate of less than 10/sup -12/. Fundamental photonic ATM switching functions, such as optical buffering and fast wavelength-channel selection, are achieved. We show our experimental results and demonstrate the high performance and stable operation of a photonic ATM switch for use in high-speed optical switching systems as an interconnect switch for a modular ATM switch and an ATM cross-connect switch.

Broadcast-and-select photonic ATM switch with frequency division multiplexed output buffers

A photonic ATM switch has been developed with frequency division multiplexed (FDM) output buffers. The switch has a broadcast-and-select network architecture using fixed-frequency-channel transmitters and a passive star configuration. Although it has a simple structure, it can provide either broadcast or multicast switching. The output buffers, which resolve cell contentions, are comprised of fiber delay lines that can easily handle signal speed of over 10 Gb/s. Experimental switching of two-multiplexed 10 Gb/s cells with a 2.8-dB power penalty demonstrated high-speed switching.

Optical output buffered ATM switch prototype based on FRONTIERNET architecture

We constructed a rack-mounted prototype photonic ATM switch based on the FRONTIERNET architecture. The advantages of the architecture are that its output-buffering scheme overcomes the bottlenecks that can occur when receiving and storing concurrent high-speed cells, and that there is no need to deal with contention resolution between input highways. The prototype has 16 input/output ports and 2.5 Gb/s transmission speed. Actually, six input ports and one output port are mounted in two racks. We demonstrated successful cell routing and buffering, and its stable operation, with 24-h bit-error-free switching operation. We also discussed problems to be solved in increasing the throughput of FRONTIERNET.

A disjoint path selection scheme based on enhanced shared risk link group management for multi-reliability service

We consider a mechanism for providing a multi-reliability service in multilayer GMPLS networks. By introducing GMPLS restoration techniques and shared risk link group management, we can provide a highly reliable protected connection service. However, there is a trade-off between reliability and efficiency of network resource usage. In addition, reliability requirements differ depending on the type of service (e.g., Internet access or leased line). Thus, we propose a mechanism for calculating an efficient route for a protected connection that can satisfy specific reliability conditions requested by customers. We also present simulation results that indicate our schemes are remarkably effective for achieving a better balance between end-to-end reliability and efficiency. We also demonstrate the quantitative relationship between availability of service and resource efficiency through simulation experiments

Proposal of scale-out control architecture of virtual wide area layer-2 switch on metro network

Power consumption of network equipment has been rapidly increasing, so it is therefore necessary to build a resource efficient network (NW). Router virtualization, which involves dynamically reallocating virtual routers to physical resources as a server virtualization, is becoming more common as a way to use network equipment effectively and robustly. Especially, edge router which is gateway of core network should be virtualized, because edge routers have many functions and resources just as servers do. A metro NW is wide area layer-2 aggregation NW that connects each users residential gateway to edge routers. To achieve edge router virtualization, the metro NW must trace the dynamic edge router reallocation by changing a route of each Ethernet flow. Furthermore, access/metro NWs occupy a large proportion of the total NW power consumption, so logically centralized control architecture suits to the metro NW to change routes flexibly because it can use resources effectively by avoiding resource deployment in many locations. However, it is not scalable. When many Ethernet flows need to be accommodated in a metro NW, it can not change routes of the flows quickly enough. Therefore, we propose a virtual wide area layer-2 switch architecture with scale-out control that can improve the route control performance even in a worst case edge router node failure by processing in parallel flow-by-flow, by considering route information, and by rebalancing the load between parallel processes dynamically. We evaluated the proposed architecture through theoretical analysis and experiments with prototype. The results showed that the proposed architecture can increase the number of flows accommodated in a metro NW.

Design of photonic ATM switch and a rack-mounted prototype

This paper describes large-capacity photonic ATM switching systems being developed that use FDM (or WDM) techniques. Our system is based on a simple star architecture with a modular structure. We show that it is possible to obtain a 320-Gb/s system that has enough S/N margin and can tolerate the polarization and frequency dependencies of optical devices. Our experiments using rack-mounted prototype modules to demonstrate the feasibility of our system, as well as successful 10-Gb/s 4/spl times/4 broadcast-and-select and 2.5-Gb/s 16/spl times/16 frequency-routing switch operations.

Proposed optical multicasting method using tunable lasers and cyclic AWGs

We present a wavelength-routing multicast (MC) packet switch based on simultaneous modulation of multi-wavelengths and symmetrical wavelength switching between two cyclic arrayed-waveguide grating (AWG) filters and tunable lasers (TLs). The proposed method requires fewer active devices compared to conventional methods. We clarify the power budget conditions needed to apply this method, and we evaluate the switch scale for the proposed method by using the specifications of commercially supplied optical devices. The feasibility of the proposed method is demonstrated through experiments on devices.

An offload method for traffic distribution based on service identification

Many functions for various network services (e.g. IP telephone, ISP connection and IP-VPN) are deployed on a broadband network, especially at the boundary between an access network and core network in the broadband network. The network service must be identified from each packet and the packet must be processed appropriately for that service. IP traffic in the broadband network is increasing sharply, so traffic distribution based on service identification may bottleneck when many different network services are provided in the network. Therefore, we propose an offload method for traffic distribution based on service identification to service processing parts, which process the packets for each network service appropriately. This method does not require additional functions in user terminals, and it more scalable than the method in which all traffic undergoes the service identification process. However, control of the proposed method is slightly more complex, so we established a control procedure and checked it in combination with user terminals. In addition, we evaluated by theoretical analysis the scalability of traffic distribution with offload compared to the method without offload. The results showed that the proposed offload method can increase the scalability of traffic distribution based on service identification.

Feasibility of Q-factor-based level design for photonic packet-switching systems

The feasibility of designing the optical level of a fast packet-switching system when Manchester-coded signals are used, has been confirmed by Q-factor measurements. These measurements show that such systems can be designed by using a simple S/N design even if the semiconductor optical amplifiers are in a saturated condition.