Koji Sasayama

FRONTIERNET: frequency-routing-type time-division interconnection network

This paper describes a photonic time division multiplexing (TDM) highway switch, called FRONTIERNET, that uses optical frequency as routing information. This switch architecture can be applied to asynchronous transfer mode (ATM) switching systems. The N/spl times/N switch consists of N tunable frequency convertors and N frequency-division-multiplexed (FDM) output buffers connected through an N/spl times/N frequency router. The router can interconnect N input highways with N output highways in a completely noninterfering way. It is possible to address each output highway uniquely by the choice of frequency (frequency routing) and each output highway can receive any given frequency from only one input. This switch architecture therefore has three advantages: its novel output buffering scheme achieves the best possible performance, there is no need for a complicated contention resolution mechanism between input highways, and there is no splitting loss of the transmitted optical power. An experimental switch with a one-cell FDM buffer was constructed. The tunable frequency convertor based on fast tunable frequency lasers can transmit high-speed optical cells to which frequencies are assigned on a cell-by-cell basis. The frequency router is an integrated-optic arrayed-waveguide grating 16/spl times/16 filter produced by using planar-lightwave-circuit (PLC) technology. The one-cell FDM output buffer based on optical fiber delay lines can store FDM cells and select only one cell at each timeslot over the output highway. A 2.5-Gb/s experimental switch was successfully operated, And an experimental FDM loop buffer was also demonstrated. This stores two cells at a data rate of 2.5 Gb/s. The bit error rate (EER) of the cells after up to 10 circulations is <10/sup -9/. The performance of the buffer in terms of the probability of cell loss and the cell wafting time in the buffer is analyzed numerically. It is concluded that fewer optical buffers are needed to satisfy the desired probability of the cell loss compared with the conventional electronic buffers. The scale of the switch can be expanded in a modular fashion in two ways using a multistage frequency router and a multistage switching network. And the multihop FRONTIERNET architecture is proposed to reduce the required frequency channels rather than the single-hop FRONTIERNET. The switch scale is also very easy to expand by connecting the frequency-router-based switching submodules.

Photonic FDM multichannel selector using coherent optical transversal filter

This paper describes a photonic frequency-division-multiplexing (FDM) multichannel selector using a coherent optical transversal filter and discusses its application to a photonic FDM highway switch. The selector can select several arbitrary channels out of several multiplexed frequency channels. The selector function takes advantage of the fact that the filter can express arbitrary frequency characteristics. An experimental 16-tap filter is fabricated according to silica-based-waveguide technology, which can monolithically integrate a variety of optical components. Arbitrary channel selection and signal transmission characteristics are confirmed by measuring the frequency characteristics of the selector and the bit-error-rate performance. >

Demonstration of 30 circulations in a transparent optical-loop buffer for 2-channel FDM packets at a data rate of 2.8 Gbit/s

Summary form only given. Buffering is indispensable in packet-switching systems. Optical frequency-division multiplexing (FDM) techniques make it possible to design a compact buffer fabric. A transparent optical-loop buffer is one of the simplest buffering schemes; the packet storage time corresponds to the number of circulations in a loop-connected optical fiber. In this paper we present an experimental optical loop-buffer employing a differential receiver which can receive power-fluctuated packets. The proposed system can preserve two FDM-packets for up to 30 circulations and provides frequency-channel expandability.

Optimization of light-path configuration order in IP over WDM networks using fast traffic matrix estimation

We propose an algorithm for determining light-path configuration order to minimize the reconfiguration time from a disrupted state to a suboptimal state. It computes a near-optimal solution within one minute on a 1000-node network.

Multi-staged network restoration from massive failures considering transition risks

In a scenario of restoration from massive failures, a network is repaired through multiple restoration stages because availability of repair resources is limited. In a practical case, a network operator should assure the reachability of important traffic in transient stages, even as risks and/or operational overheads caused by stage transitions are suppressed. We discuss the novel problem of optimizing both traffic recovery ratio and transition risks caused by paths switching operation. We formulate our problem as linear programming, and show that it obtains Pareto-optimal solutions of traffic recovery versus transition risks. We also propose a heuristic algorithm for applying networks consisting of a few hundred nodes, and it could produce sub-optimal solutions within 4% difference from optimal solutions.

Theoretical and Experimental Study of Statistical-Decision Method for Link-Capacity Adjustment

To utilize network resources effectively and guarantee the system reliability in Internet exchanges (IXs) in the future, the use of photonic IXs that employ optical cross connects and generalized multiprotocol label switching is considered. This paper presents a theoretical and experimental study of link-capacity adjustment for a photonic IX employing a statistical-decision method for traffic monitoring. We present parameter estimation of the statistical-decision method in detail considering the traffic characteristics in IXs. Then, experiments on the link-capacity adjustment are presented. The first experiment shows the link-capacity adjustment of an optical path to evaluate path addition from one path to two and path deletion from two optical paths to one. The second experiment shows the link-capacity adjustment using multiple paths. We confirmed that there is no packet/frame loss in either experiment during the transmission of demo traffic, which simulates daily traffic changes.

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.

Content aware routing: A content oriented traffic engineering

Content transfer, e.g. video transfer, is now becoming major traffic in the current Internet. Content transfer originally has a content oriented feature of “wherever content is retrieved, users only take care of what content they obtain”. Conventional traffic engineering aims to obtain optimal routes for traffic between ingress and egress router pairs, which has “location oriented feature, i.e. where to connect”. With content oriented feature of user demand for content traffic, traffic engineering can be changed towards content oriented routing design. In this paper, we propose a novel content oriented traffic engineering, named CAR (Content Aware Routing). In CAR, routes are designed for content and egress router pair, i.e. content traffic towards a receiver-side router. Content demand can be flexibly distributed to multiple servers(repositories) providing the same content, which means content can be obtained from anywhere. With numerical examples by linear programming formulation, we comparatively evaluate CAR with comparing with combination of CDN and traffic engineering, i.e. location oriented designs. Numerical results show that CAR improves maximum link utilization significantly with slight increase of network resource usage.

Router-OXC cooperation for fault recovery employing GMPLS control plane for photonic IX

This paper proposes fault recovery procedures to improve the reliability of photonic Internet exchanges and presents experimental results that confirm the feasibility of employing these procedures for the first time. The proposed procedures employ cooperation between routers and optical cross-connects using over-lay model generalized multi-protocol label switching control plane to utilize network resources efficiently.

Theoretical and Experimental Study of Statistical Decision Method for Link Capacity Adjustment in Photonic IX

This paper proposes a statistical decision method for link capacity adjustment and estimates the decision parameters using a numerical simulation in order to achieve stable operation of the proposed method. The results of the experiments conducted using multiple paths confirm the effectiveness of the proposed method.