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FEATURE FIBRE OPTIC SYSTEMS


Where Fibre is Heading in the Long Term Growing Pains By Ed Cady, Technical Market Manager, Siemon


In the world of data and optical communications, Ethernet has expanded well beyond the original LAN section of the network that it has dominated for many years. Responding to Ethernet’s expansion and absorption of rivals, other interfaces like Fibre Channel have created newer standard interface versions using a ‘convergent tunnelling’ method. This preserves the native Fibre Channel protocol and transmits it over an Ethernet physical transport system.


Hundreds of interfaces from the IT, telecoms, audiovisual, security and industrial/instrumentation markets seem to be converging on Ethernet as the ‘common transport’ infrastructure. Ed Cady looks into the future and comments on how fibre might evolve at 40/100Gb and beyond.


Ethernet rules ok


Recently, the Ethernet community has evolved its technology to converge LAN with SAN into one physical network. This was partially accomplished with the recent implementation of Ethernet standard 10GBaseCR, which uses serial transmission over a two-pair ‘single lane’ twin-axial copper link. This convergence has lead to


the creation of Fibre Channel over Ethernet, a specification that helps to preserve the native protocol and its installed base, yet allows Ethernet infrastructure to be used. The InfiniBand community has similarly created a specification known as Remote Direct Memory Access over Converged Ethernet (RoCE - pronounced ‘Rocky’). Besides Fibre Channel, other data


storage interfaces such as NAS, iSCSI, iSATA and ATA over Ethernet are now all tunnelled over Ethernet using twin-ax 10GBaseCR copper cabling and SFP+ connectors. These storage interfaces can also be tunnelled over longer distances using Ethernet 10GBASE-T using category 6A and category 7A cabling systems. There are defacto standards using


these multi-protocols on so-called ‘collapsed architectural fabrics’ like the Unified Computing System, which also use SFP+ cabling. Besides UCS, there are several other defacto-standard unified style networks which also use the SFP+. Many have only recently come


across the concept of the SFP+ single- lane active connector. Its profile is being raised by recent developments in faster Ethernet technologies and the 25/26/28 Gbps QSFP++ active


10 NETCOMMS europe Volume II, Issue 1 2011


Many have only recently come across the concept of the SFP+ single-lane active connector.


Ethernet ‘category’ cabling systems, as is the HDBaseT signalling and HomePlugAlliance’s cabling adapters. So one could predict that the shielded category 6A/7A, SFP+ and QSFP+ are the three primary multi-protocol interconnects for now and for several years.


lane is actually being co-developed alongside 50Gbps per lane. This optical interface is beyond the capabilities of the LightPeak interface and could supplant even Ethernet, InfiniBand, Fibre Channel and the many other interfaces in newer data centres within five years.


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connector module. One could wonder whether all of


these ‘xyz over Ethernet’ interfaces will expand and use the developing QSFP++ module and cabling system, which is being standardised through the SFF-8661/2/3 specification. Ethernet standards 40GBaseCR4, 40GFCoE and InfiniBand 40G QDR are all using the same four lane QSFP+ connector, module and cabling. The SAS storage interface uses QSFP+ Active Optical Cables for longer reach applications, as does the video networking standard CameraLink-2. Will these various interface


communities stay converged using the new QSFP++ connector system for next generation 100Gb/s standards such as 100GBaseCR4, 100GFCoE, 100GFC SAN and InfiniBand 100G EDR? Only time will tell. There are many other convergent


interfaces like Fibre Channel over InfiniBand, USB attached SCSI, USB over SATA and SATA over USB. HDMI has recently released


its new revision-1.4 specification. This specification has 1Gbps Ethernet running through the new microHDMI cabling system. However, HDMI and DVI video signalling are already run through


Interface collisions


Technology is currently facing a potential round of interface collisions, convergence and collapsed interconnect. It is starting at the desktop level with DisplayPort, USB, SATA, HDMI and PCI-E (the new PC expansion-card interface) all being converged and transformed to the new multi-protocol LightPeak optical-only single fibre interface. It is rumoured that LightPeak might replace short-reach Serial Attached SCSI as well. It seems that there are both 10Gbps and 28Gbps versions of LightPeak.


In the fast lane


At the 25 to 40Gbps per lane data rate, electrical signalling over copper has very limited cable reach; up to three metres. Active optical cabling seems to have an equal portion of the forecasted volume versus copper at these data rates. It’s no wonder that there’s another


generation looming! A new optical interface which will be supported by chips in development that currently work (in labs) at 50Gbps per lane at distances of up to 2km. The next ‘next’ generation with 100Gbps per


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