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Internet-2 Fall Meeting Optical Panel. Tuesday September 20 th 2005 brian.smith@meriton.com. Electrical vs Optical Switching in R&E Networks. Capabilities Economics Reliability. Capabilities. Economics. The most cost effective solution is dependent on
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Internet-2 Fall Meeting Optical Panel Tuesday September 20th 2005 brian.smith@meriton.com
Electrical vs Optical Switching in R&E Networks • Capabilities • Economics • Reliability
Economics • The most cost effective solution is dependent on • The architecture of the node (East-West / Mesh) • How much traffic is required to add/drop at the node • How much traffic is Pass-through at the node • OEO and OOO available in same node for most cost effective solution over network lifespan.
Economics Example 1: All traffic is ‘available’ for add/drop at the node but can be pass-through if necessary – assumes 10GigE traffic OEO is more cost effective at all capacities
Economics Example 2: Fixed capacity of 32 wavelengths – %age of traffic available at the node is variable – Assumes 10GigE traffic OOO more cost effective with increasing pass-through traffic
Economics Example 3: QUILT Network Model (October 2004) : Metro 2-1 node. Mix of 2.5G(50%) and 10G(50%) traffic. 25% pass-through traffic (10G) OOO / OEO equally cost effective at Day-1 :OEO becomes more attractive as more capacity is added
Reliability OPTICAL ELECTRONIC Electronic switching is a well proven, field deployed technology. With increase in market volumes (2008) Optical ROADM reliability will be on a par with electrical reliability
Questions • Are there performance issues related to OOO vs OEO ? • With OOO, the express (pass-thru) wavelengths will traverse a longer optical path, though more optical amplifiers and filters than the equivalent OEO solution so . . • The required OSNR for the OOO case will be higher than OEO due to the build up of non-linear impairments and a reduction in the dispersion window. • OOO will experience more pass-band narrowing through the cascaded optical ROADM – therefore more signal distortion effects must be managed within the link engineering. • OOO does however provide dynamic gain flattening and power equalization. • Optical amplifiers with advanced transient suppression and monitoring features are required for OOO. • The number of OEO nodes traversed will eventually be limited by jitter accumulation along the path. • If design is within link budget limitations, both will perform equally well
Questions • What are the advantages/disadvantages of OOO vs OEO related to monitoring ? • An Electronic switch fabric has access to layer 0, 1 and higher Performance Monitoring which provides for remote network troubleshooting and for fast, effective protection switching. • OOO has access to optical power/OSNR measurement only. • Electronic switching fabrics allow loop-backs to be set remotely which cuts the cost and time required for network troubleshooting – there is no equivalent in an OOO system.
Questions • What are the advantages/disadvantages of OOO vs OEO related to switching especially in providing dynamic capabilities ? • OEO is by definition non-blocking and so multi-degree ring interconnection and mesh networking are simple compared to OOO from an engineering and control perspective. Where the number of pass-through wavelengths is small, OEO provides a more cost effective solution. • In the cases where significant pass-through traffic is required (in east west or multi-degree networks), OOO provides a more cost effective solution than OEO. • For cases where the traffic is a mix of 2.5G and 10G, add/drop and pass-through at a node, the cost differential is less well defined (as was discussed re the Quilt network model !) • In large rings and multi-degree cases OOO requires complex path dispersion management which is fiber type dependent.
Questions • Which is better suited beyond 10G and what are the advantages/disadvantages of each ? • From a cost perspective, OOO is better suited to 40G traffic when pass-through wavelengths are required at a node. • For 40G pass-through, OEO would cost a minimum of 4 times that of an equivalent 10G port – switching electrically at native 40G rates is not on the development radar • For OOO and depending on the 40Gbps+ technology used, there will be a limit on the number of cascaded OOO hops in a chain (ring or mesh) before pass-band narrowing starts to cause significant ISI. • 40Gbps+ will require more strict control of dispersion in OOO systems and will have a reduced OSNR tolerance compared to 10G systems.