Douglas Marquis

A wideband all-optical WDM network

We describe some of the results of the Advanced Research Projects Agency (ARPA) sponsored Consortium on Wideband All-Optical Networks in developing architectures, technology components, and applications for the realization of scaleable, wideband, and transparent optical wavelength-division multiplexing (WDM) networks. Our architecture addresses all-optical transport over the wide, metropolitan, and local areas. It utilizes wavelength partitioning, routing, and active multiwavelength cross-connect switches to achieve a network that is scaleable in the number of users, data rates, and geographic span. The network supports two services which can be point-to-multipoint or multipoint-to-multipoint simplex or duplex connections. The A service is a transparent physically circuit-switched service and the B-service is a scheduled time-slotted circuit which is transparent within its time slots. We have developed a 20-channel local and metropolitan area WDM testbed deployed in the Boston area, now undergoing characterization and experimental applications.

Security issues in all-optical networks

All-optical networks are emerging as a promising technology for terabit per second class communications. However, they are intrinsically different from electro-optical networks, particularly because they do not regenerate signals in the network. The characteristics of all-optical network components and architectures manifest new and still unstudied security vulnerabilities but also offer a new array of possible countermeasures. We focus on two types of attacks on the physical security of the network: service disruption, which prevents communication or degrades quality of service (QoS), and tapping, which compromises privacy by providing unauthorized users access to data which may be used for eavesdropping or traffic analysis.

Bossnet: an all-optical long haul networking testbed

Bossnet (Boston South Network) is an optical networking testbed developed for the purposes of expanding knowledge about long haul communication using fiber optic transmission technology, and for demonstrating futuristic applications that demand very high bandwidths. Bossnet is the creation of the Defense Advanced Research Projects Agency (DARPA), the Massachusetts Institute of Technology, Lincoln Laboratory, and Qwest Communications. The network became active in December of 1999 and is planned to remain operational through December 2003. This paper describes the infrastructure, reviews our initial experiments, and gives an overview of our plans.

Autonomous Timing Determination in a Time-Slotted WDM All-Optical Network

Introduction: There are several network services provided by the 20 wavelength all-optical network (AON) testbed deployed in the Boston metropolitan area[ 11 by the Consortium on Wideband AllOptical Networks[2]. One is a scheduled time and wavelength division multiplexed service which supports multiple simultaneous and independently optically routed connections for users with data rates variable from -10 Mbps to 1.244 Gbps. A key feature of this T D W M service is the time-slot synchronization required for the efficient use of network resources, especially when data is transmitted in short high-rate bursts or time-slots. We demonstrate autonomous transmitter/receiver synchronization over a metropolitan area testbed. This allows signals from widely distributed sources to mesh without collision on common a wavelength at a common fiber, router or other time-shared network resource. TDWWDM Service Description: In the TDM/WDM communication service (which we call the AON B-service) transmitters and receivers are assigned time slots lasting 1.953 ps into which data is encoded at a channel rate of 1.244 Gbps. 128 time slots are defined for each 250 ps frame. Each time slot is carried on one of 20 optical wavelengths each of which may be independently routed or broadcast to different destinations via the hierarchical AON architecture (Fig. 1). Users are scheduled sets of time slots and wavelengths for their transmission and connection needs. Fig. 2 illustrates the mapping of user sessions across time slots and channel frequencies [3]. For each wavelength, time slots not scheduled for one user are available to other users. Fast-tuning transmitters may be assigned one time-slot/wavelength schedule and fast-tuning receivers[4] another, depending on the ne:eds of their users. The timing problem arises when time slots originating in widely separated nodes of the network (e.g. the optical terminals in Fig. 1) must mesh without collision on a common wavelength at (a common network resource such as a fiber, star coupler, router, switch or other component. For high network efficiency, scheduled signals must never collide at a given time on a given wavelength in a given resource. In addition, only insignificant amounts of dead or guard time must be allotted to separate successive scheduled transmissions on a given wavelength and resource. Because transmitters and receivers have distinct schedules, receivers also must be able to identify the slot number of the received data in order to tune at the right time to the appropriate frequency and to correctly deliver data to the user channels. Autonomous Timing in the AON: The time-slotted WDM B-Service of the AON testbed derives its timing from a 1.244 GHz master oscillator which is injiected into the network at Level-1 and propagated downward to the L-0 hubs and the OTs via an out of band optical control channel. The 1.244 GHz signal is recovered at the optical terminals (OTs) and usedl to generate a 4 kHz (250 ps) frame reference. Since the frame reference for all OTs are derived from a common master oscillator they are frequency-locked but possess an arbitrary phase offset determined by the initial state of the counters used to generate the frame clock from the 1.244 GHz master and the differences in propagation delay. Absolute phases at are established when a B-service connection is first made. Determination of clock phase relies on detection of a valid-data transmission window in the received signal stream and the recognition of valid 8B/10B data code-words within that window (]Fig. 3). This takes place autonomously at startup by the optical terminals and requires no test-equipment. The receiver timing offset (delay) is determined relative to existing metropolitan-area (L1) traffic by :sliding in time the received valid data window (which is slightly longer than the user data payload) to center the position of the received data payload within the window. The edges of the valid data window are sensed by FIFO status indicators in

Transmission modes, cross talk requirements, and performance of the circuit-switched A-service in the all-optical network

In summary, we have demonstrated uniform performance of the all optical network (AON) A-Service under Level-O broadcast and Level-1 routed, multicast and broadcast operation. We have demonstrated multihop operation with conventional wavelength changing. Finally, we presented measurements on the potential impairments of optical beat noise cross talk in transparent optical networks and showed how the AON manages such potential effects.

Performance of a wavelength-routed all-optical network at over 100 Gigabit/s

There are several network services provided by the 20 channel (50 GHz spaced) all-optical network (AON) testbed deployed in the Boston metropolitan area. In this work, we report on a new metropolitan area service with 10 Gbps access rates per channel using tunable transmitters and receivers to support, for instance, SONET OC-192 users. We demonstrate operation of more than 10 independent local and metropolitan channels for a total data rate exceeding 100 Gigabit/s. This is the first time such high rates have been demonstrated in a dense WDM system utilizing all-optical wavelength routing and partitioning for wavelength and channel re-use.

Control and interfaces for an all-optical network testbed

We describe some of the control and interface techniques employed in the construction of an all-optical network testbed fielded in the Boston metropolitan area. The network was developed by a consortium of AT&T Bell Laboratories, Digital Equipment Corporation, and the Massachusetts Institute of Technology under a grant from ARPA. The network testbed contains local, and metropolitan area nodes that support optical broadcast and routing modes. Electronic access is provided through optical terminals that support multiple services having data rates between 10 Mbps/user and 10 Gbps/user. Applications include video, support for ATM traffic, and telemedicine applications.

Description of all-optical network test bed and applications

We describe an all-optical network testbed deployed in the Boston metropolitan area, and some of the experimental applications running over the network. The network was developed by a consortium of AT&T Bell Laboratories, Digital Equipment Corporation, and Massachusetts Institute of Technology under a grant from ARPA. The network is an optical WDM system organized as a hierarchy consisting of local, metropolitan, and wide area nodes that support optical broadcast and routing modes. Frequencies are shared and reused to enhance network scalability. Electronic access is provided through optical terminals that support multiple services having data rates between 10 Mbps/user and 10 Gbps/user. Novel components used to implement the network include fast-tuning 1.5 micrometers distributed Bragg reflector lasers, passive wavelength routers, and broadband optical frequency converters. An overlay control network implemented at 1.3 micrometers allows reliable out-of-band control and standardized network management of all network nodes. We have created interfaces between the AON and commercially available electronic circuit-switched and packet-switched networks. We will report on network applications that can dynamically allocate optical bandwidth between electronic packet-switches based on the offered load presented by users, without requiring interfaces between users and the AON control system. We will also describe video and telemedicine applications running over the network. We have demonstrated an audio/video codec that is directly interfaced to the optical network, and is capable of transmitting high-rate digitized video signals for broadcast or videoconferencing applications. We have also demonstrated a state-of-the-art radiological workstation that uses the AON to transport 2000 X 2000 X 16 bit images from a remote image server.

Demonstration of multigigabit/per second services over a 20-channel WDM wavelength-routed all-optical metropolitan-area network

An experimental all-optical, wavelength-routed network testbed has been constructed in the Boston metropolitan area. The network has 20 optical channels, space by 50 GHz and provides dedicated circuit-switched wide-band service at user defined modulation formats and rates up to 10 Gbps, and time-slotted WDM services for medium and low-rate users. We are now characterizing the deployed network which spans over 87 km interconnecting four all-optical local-area networks in Littleton, Lexington, and Cambridge Massachusetts. We discuss wavelength sharing and reuse, local broadcast, routing, multi-cast and multi-hop connections at 1.244, 2.488, and 10 Gbps. We present the system design and the performance (e.g. BER and cross-talk) of local-broadcast, metropolitan-area-routed and broadcast transmission modes.