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Applying undersea technologies to Project OxygenWilliam C. MarraTyco Submarine Systems Ltd.Holmdel, N. .Tel: 732-949-7951; FAX: 32-949-3833email: marra@submarinesystems.com

For the last 10years undersea fiber optic connectivity has been used on a global scale to provide one of themost cost effective transmission mediums for international communications. Project Oxygen is a visionarynetwork whose construction will be phased in time and connect more th an 50 countries with up to 160,000km of new undersea fiber optic cable. The network will integrate the newest and most sophisticatedtechnologies for providing ubiquitous end-to-end customer telecommunications services. Some of thetechnologies to be included are: Dense Wa v el en b ~ ivision Multiplexing (DWDM ) , undersea BranchingUnits (BUS) and Erbium Doped Fiber Amplifiers (EDFAs) as they apply to undersea applications,Asynchronous Transport Mode (ATM ), Synchronous Digital Hierarchy (SDH ) and P lesiochronous DigitalHierarchy (PDH ) transport capabilities and Network Management Systems (NM S).In order to better understand how these technologies are applied to Project Oxygen, we start by itemizingthe high level requirements that are applied to achieve the end-to-end network objectives of Projec t Oxygen.These include: global connectivity, low cost access to bandwidth, fast restoration, circuit provisioning andbandwidth on dem and, and centra lized monitor and control of the network.Global connectivity, low cost access to bandwidth and fast restoration can be realized by constructing thenetwork as a complex of interconnected loops. Each loop includes a multiplicity of undersea cablesegments that terminate at cable landing stations. Each cable segment includes up to fo ur pair of opticalfibers and undersea repeaters equipped with ED FA technology to provide optical gain of th e transm issionsignal. In some cases, BUSare installed in the main trunk cable and are used to split the fiber connectivityand route traffic to cable stations not necessarily needing the traffic capacity carried by entire underseacable. In all cases, the transmission capacity is 160 Gb/s per fiber pair and it is made up of 16 WDMca m er channels each channel operating a 10 Gb/s. Thus a four fiber pair cable segment can carry up t o 6 4individual WD M channels or 640 G b/s of transmission capacity. These large transmission capacities drivedown the access cost to bandw idth. As the cable segments close on themselves to form loops, it is possibleto take advantage of SDH ring switching technologies by sub divisi on of the 64 channels into 32 serviceand 32 protection channels. This results in a layered WDM ring network which suppo rts 32 independentlyoperating fast bi-directional line switching logical rings. As the loops are inter-connected, globalconnectivity is achieved. Thus three of the high level network objectives are attained: global connectivity,fast restoration and the high capacity undersea technology provides the basis of low cost access tobandwidth. These concepts are illustrated in Figure 1where two loops are show n.Each cable landing station is a network node which provides universal inter-operability between the highcapacity undersea cable transmission medium and the in-country telecommunication service providersnetwork. This is accomplished by providing a standardized STM-64 interface between the equipmentwhich terminates the undersea cable segments and the equipment that interfaces to the in-land serviceproviders network. This equipment that faces in-land provides several core h c t i o n s including ATM,SDH, and PD H customer traffic interfaces.

mailto:marra@submarinesystems.commailto:marra@submarinesystems.com

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Single Loop HasI Up To 64 Channels(32 Srv.& 32 Protn1

LayeredRings

KEY:0 able Station (CS)M Undersea RepeatersIBUBranch Cable& ain Trunk CableCustomer TrafficFigure 1 Illustration of inter-connected undersea cable loops & the formation ofWD M layered ring structures within a single loop having flexible connectivity.

Circuit provisioning, bandwidth on demand, and centralized monitor and control of the network areachieved by embedding in the transmission facilities an overlay Wide A rea Network (WA N). This WANconnects to the cable stations' Local Area Networks (LANs) and provides routing capa bilities to and fromthe Network Operations Centers (NOC s) at gateway cable stations. The LAN established at each cablestation is used to integrate that cable station's Element Managers (EM S) which are needed to m onitor andcontrol the transmission Network Elements (NEs) and undersea wet-plant equipment. This NMShierarchical structure and L A " communications infrastructure is shown in Figure 2.The NOC s ar e duplicated with synchronized data bases. From any NOC it is possible to manage the entirenetwork. This includes identifying problems, issuing corrective procedures, taking customer servicerequests and then configuring traffic acro ss the network between customer interfaces, billing for servicesand setting the desired security management structure of the network.

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Service Management:

Netw ork Management:Configuration ofTraffic PFaul Identification

NE * * * NE NEE * * *Undersea NEs, Transmission NEs NOC: Network Operations Centere.g., Wet-Plant Facing In-Land CS: Cable StationSupervisory, Power Network EM: Element ManagersNE: Network Element1ransmissionCable Station (CS)Figure 2: Network Management System Communicationsand Feature Infiastructure

Conclusion:It has been 10 years since the first undersea fiber optic cable system (TAT-8) was installed between the USand Europe. Since that time market pressure has driven undersea cable system transmission capacitie s, onthe average, to double each year driving down the circu it cost of international communications. In th at t h ethere have been some key enablers such as the incorporation of EDFAs in undersea repeaters, a betterunderstanding on non-linear transmission effects which have driven improvements in fiber and cab le designas well as new dispersion m anagement techniques. Undersea qualified W DM technologies such as couplers,narrow-band filters, grating filters and stable narrow line-width lasers have added greatly to capacityincreases. As capacities increased, it was necessary not only to focus on achieving higher transmissioncapa cities for point-to-point networks, but to consider alternative network configurations which providefast automatic restoration with overlay NMS infrastructures that support a vast array of features whichmake it possible to remotely manage global networks. These undersea technologies are app lied in varyingdegrees across many undersea cable projects; however, Project Oxygen provides a unique opportuni ty tofocus all of these technologies to one ubiquitous network on a global scale.References:1. H.D. Howard, et.al., Deploying the Worlds Largest Undersea Fiber Cable System, NFOEC-98Proceedings, September, 1998.