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FEATURE DATA CENTRE OPTICS


entry is crucial. Pure technology is not the only consideration, says CommScope’s Kolesar and he offered a cautionary tale. ‘IEEE 802.3 defined an Ethernet physical layer


at 10Gb/s called 10GBASE-LX4,’ he recalled. ‘It was a four-wavelength interface, designed to enable the legacy plant of that day, which was OM1 and OM2 multimode fibre.’ Te LX4 used wavelengths in the 1300nm range, which is typically used with singlemode fibre. As such it employed singlemode lasers with the more stringent singlemode alignment tolerances rather than the cheaper VCSELs that are used today. ‘Te technology was eclipsed by the adoption of


OM3 fibre which allowed a simpler, serial, VCSEL-based solution known as 10GBASE-S, which is what still is in use today,’ said Kolesar. He also noted that an exclusivity agreement prevented LX-4 from being well sourced and supplied – consequently its market penetration was small. Heeding the lessons of the past, both fibre and


transceiver manufacturers hope to encourage adoption of SWDM-based products by ensuring that standards are in place early in the process so that vendors can develop products to a common specification.


Structured cabling standards Multimode fibre standards are developed under TR42, the structured cabling committee of the Telecommunications Industry Association (TIA). CommScope’s Paul Kolesar has chaired the TR42.11 subcommittee on fibre optic systems for around 10 years. He said: ‘I was the one who introduced OM3 and OM4 to the industry and this will be my third attempt at bringing an evolution to multimode transmission through wideband fibre,’ he noted. Tird time lucky, it would seem. At the group’s


October 2014 meeting, CommScope’s proposal to initiate a project to develop the wideband multimode fibre specification received significant


Cabling Evolution Map - Ethernet Examples Data Rate 10G


Parallel TX


RX 40G 100G 25G


Parallel TX


RX N/A


10G, 25G Parallel


w/ WDM TX


RX


@fibresystemsmag | www.fibre-systems.com


SWDM enabling 4x fiber count reduction


Imagine running 10G, 40G and 100G


over the same cable plant using duplex LC connections


Legend 400G N/A


parallel fiber transmission WDM transmission WDM + parallel transmission


Cabling evolution or revolution: Parallel cables in combination with shortwave WDM will enable cost-effective 100G and 400G transmission over multimode fibre


support and was able to get underway. Te output will be a new fibre specification to be published as TIA-492AAAE. ‘Projects can get started in any number of


ways,’ explained Kolesar. ‘With this particular one we had worked behind the scenes with a number of the key players so that when everyone felt


This will be my third attempt at bringing an evolution to multimode transmission through wideband fibre


well-enough prepared we went in together to make a multi-company proposal and that was quite powerful.’ ‘We are hoping that most of the technical work


will be completed sometime in early to mid-2016 time frame,’ said Kamino from OFS. ‘If you are familiar with the standards process you know that necessarily having the technical agreement does not mean that the document published in that time frame but everyone has a pretty good idea of what is going on.’ Kamino notes that although standards


Glimpse of the future: CommScope and Finisar demonstrated 100G transmission with 225m reach over WBMMF at OFC 2015 in Los Angeles


18 FIBRE SYSTEMS Issue 9 • Autumn 2015


development is a time consuming, complex process, it is a necessary process to deliver a well-balanced, low-cost solution. He said: ‘What you do not want to do is optimise the fibre without any idea of the limitations of the devices and systems. Tat is why we try and get input from all of these different groups.’ Not only does this entail


working with manufacturers of fibre and cable, but also working with other standards groups to make sure that the new hardware will be able to support future applications. Standards bodies are always anticipating the


next step in technology. ‘Te IEEE is likely to initiate a study group for 50 Gigabit Ethernet within the next two plenary meetings, say within the next six months or so,’ said Kolesar. Te scope is likely to include a four-lane variant to provide 200-Gb/s links. In addition he notes that the International Committee for Information Technology Standards (INCITS) T11 committee, which defines Fibre Channel interconnection schemes, is already considering the next generation of Fibre Channel interface that includes single-lane and four-lane variants based on 50Gb/s. SWDM would allow both of these four-lane standards to be delivered using a two-fibre duplex interface. ‘It is also possible that these applications standards bodies will revisit existing data rates to define next-generation SWDM variants for 100G or 128G Fibre Channel,’ Kolesar added. Te standards work will certainly not end


there. ‘Tis opens up new areas of growth beyond the current standards that are being worked on such as 100G or 400G. Tere is already talk of speeds beyond 400G, and this [WBMMF] offers a novel way of being able to support these data rates,’ said Kamino. He concluded: ‘Te advent of WDM coupled


with higher speeds for VCSELs and multimode fibre will make it possible to achieve 400Gb/s and even 1.6Tb/s in compact cable structure, such that multimode fibre links are likely to remain the low-cost paradigm in enterprise data centres for years to come.’l


CommScope


CommScope


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