CONSOLIDATED METRO CABLE LANDING STATIONS

1 CONSOLIDATED METRO CABLE LANDING STATIONSW hitepaperWToday s global network is composed of numerous submarine and terrestrial networks stitched together to interconnect all major continents, except Antarctica. When a submarine network lands, it does so in the traditional CABLE LANDING station (CLS), which houses network equipment facing both the submarine and terrestrial networks. The inland METRO network is where the major Point-of-Presence (PoP) typically is located, meaning a terrestrial backhaul network from the CLS to the inland PoP is commonly implemented, as illustrated in Figure 1. For a variety of reasons mostly due to the undersea operating environment and transoceanic distances traveled the submarine network industry took different network technology paths from their terrestrial brethren for decades. As a result, the submarine-to-terrestrial demarcation point lies within the CLS, where these divergent networks meet.

2 As terrestrial networking technology is increasingly leveraged in the CLS, this inefficient network demarcation point has come into question, and frequently is being eliminated to allow for seamless global networking from METRO PoP to METRO Traditional CABLE LANDING station , on the Beach The traditional CLS houses the Submarine Line Terminating Equipment (SLTE) and SDH Interconnection Equipment (SIE) that, together, form one end of the optical link. The CLS also houses Line Terminating Equipment (LTE) that forms one end of the terrestrial backhaul network, which connects the CLS to the inland METRO PoP. The demarcation point is situated between the wet and dry networks, as shown in Figure 2, and commonly is located between the SIE and the Terrestrial Line Terminating Equipment (TLTE). By leveraging several new technologies such as coherent detection and Remote Optical Add/Drop Multiplexers (ROADMs), the housed CLS network equipment can be minimized significantly, with most remaining functionality physically moved into the inland METRO PoP.

3 This move is made possible by virtue of the increased reach afforded by coherent detection and the photonic switching capabilities of ROADMs, the robustness of which has been proven for a 1. CLS to METRO network PoP via the terrestrial backhaul networkCable LANDING StationMetro NetworkInland PoPSubmarine NetworkTerrestrial BackhaulFigure 2. Traditional CLS design, on the beachWetPlantCable LANDING StationTerrestrial BackhaulSubmarine-Terrestrial Network Demarkation PointMetro Inland PoPMetro NetworkIntelligentSwitchTLTETLTESIESLTET echnology Enablers: 100G WaveLogic 3 and ROADMs Ciena s coherent transmission technology, known as WaveLogic, enables several new features that allow network operators to rethink how they have designed their networks in the past. The latest version of WaveLogic introduces industry-leading Soft Forward Error Correction (FEC), which greatly increases achievable distances to open up new possibilities related to CLS designs.

4 The significantly longer achievable distances afforded by WaveLogic especially when coupled with coherent-optimized uncompensated wet plants often allow for moving the submarine wavelength termination point from the CLS all the way inland to the METRO PoP. These incoming wavelengths are optically 2 Figure 3. Inland METRO PoProuted inland using either fixed filters or flexible ROADMs; the latter allow for remote control and are key enablers of agile photonic networks. Keeping wavelengths in the optical domain for as long as possible reduces latency, requires equipment that consumes less power and space, and reduces the operational complexity of the network as a longer reach afforded by Ciena s WaveLogic also often allows for the complete removal of the face-to-face terrestrial backhaul terminals. This removal is possible because sufficient link budget is available to route wavelengths coming from submarine network to traverse the terrestrial backhaul distance, from the CLS to the inland METRO PoP, without the need for any REGENs.

5 This simplification significantly reduces network cost, latency, complexity, and power/space consumption, which helps increase network operator competiveness. By leveraging both WaveLogic and agile ROADMs, the network operator can greatly simplify its network design from the submarine network all the way back to the inland METRO PoP, as shown in Figure 3. The inefficient WetPlantCable LANDING StationTerrestrial BackhaulMetro Inland PoPMetro NetworkIntelligentSwitchSLTEROADM submarine-to-terrestrial network demarcation point is eliminated by physically moving the SLTE functionality inland. Costly and inefficient client-side handoffs between the two networks in the CLS are no longer necessary. SLTE functionality can also be integrated into the same node, as shown in Figure 4, to eliminate inefficient client-side handoffs between previously distinct SLTE and METRO intelligent switches.

6 This simplifies the global network even Figure 4. METRO node consolidationWetPlantCable LANDING StationTerrestrial BackhaulMetro Inland PoPMetro NetworkSLTE + IntelligentSwitchROADM further by essentially integrating traditional CLS functionality into a METRO PoP, with only the routing of light performed by the Wavelength Selective Switch (WSS) within the ROADM left housed in the CLS. Integrating the SLTE into the METRO switch facilitates building out intelligent mesh networks. The elimination of numerous Optical-Electrical-Optical (OEO) stages significantly reduces overall network latency as well, which is a primary design target of network operators result of this technology-and-network-node convergence is the elimination of the demarcation point between what has been traditionally referred to as the submarine and terrestrial networks.

7 The demarcation point is replaced by a simpler converged network, shown in Figure 5, which, due to the seamless interconnection between land and sea, results in global networks that are simpler to design, manage, and maintain. The key functionality once housed in the CLS is now physically located in the inland METRO PoP, making it far easier to access, maintain, and physically protect a growing concern for Inland METRO PoP METRO networks are the destinations for traffic carried over submarine networks, so keeping this traffic in the photonic domain routed right into the METRO PoP yields numerous benefits, such as lower latency and cost, to both network operators and end-users alike. Advances in industry-leading WaveLogic coherent technology and ROADM-based photonic switching allow for this change in network design, especially as it pertains to the traditional CLS network design.

8 As SLTE functionality is integrated directly into the METRO PoP, and into CABLE LANDING StationInland PoPConverged NetworkMetro NetworkInland METRO PoPSLTE + IntelligentSwitchCable LANDING StationROADMF igure 5. Converged global network convergenceCiena may from time to time make changes to the products or specifications contained herein without notice. Copyright 2012 Ciena Corporation. All rights reserved. WP116 intelligent switch in particular, network design and operation are greatly simplified from both a METRO and global perspective. The METRO network becomes the centralized junction point between submarine, regional, and long-haul networks, which cost-effectively allows for direct interconnection to collocated data centers. Because METRO networks are the destination point for most traffic flowing through the world s global network, overland and undersea, making them the logical termination point for submarine wavelengths is now that changethe way you > Simplify and reduce the cost of building and maintaining CLS network designs> Improve how traffic is handed off between submarine networks and METRO terrestrial networks > Leverage new technologies to create seamless global networks from METRO PoP to METRO PoPSolution > Ciena s 6500 Packet-Optical Platform, providing 40G/100G industry-leading WaveLogic Coherent Optical Processor intelligence and photonically-switched ROADMs.

9 Allowing all-optical transportBenefits> Significant scalability to meet bandwidth growth while fully leveraging existing wet plants assets> Simple and rapid capacity increases without any changes to the existing submarine wet plant> Reduction in latency, cost, power, and space by consolidation of CLS functionality into the METRO PoP