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the active equipment required remains more expensive than multimode equipment . Further , while most data centre backbone links do not require the reach distances currently supported by singlemode fibre , which include up to 10 kilometres ( km ) for speeds ranging from 40 to 400Gb / s , hyperscale data centre backbone links often exceed the 100m maximum link length supported by multimode equipment . Hence , while multimode fibre remains the more common choice for these links , new developments in optimised reach ( ie ., 500m ) singlemode data centre solutions are expected to change the landscape of data centre architectures . And even selecting multimode fibre has become a more complex endeavour , especially with the upcoming 3rd edition of the ISO / IEC 11801 standard that will include a new type of wideband multimode fibre , designated as OM5 .
While existing OM3 and OM4 multimode fibre is specified to operate in the 840 to 860 nanometre ( nm ) wavelength range with 850nm as the optimal wavelength , new OM5 wideband multimode fibre specifies a wider range of wavelengths between 840 and 953nm to support wavelength division multiplexing ( WDM ) technology . WDM technology multiplexes multiple signals onto a single fibre using different wavelengths .
Fully backwards compatible with existing OM4 fibre specifications , OM5 fibre and WDM technology offer the theoretical capacity to either increase transmission speeds or reduce fibre strand counts by a factor of four . For example , using standard OM3 or OM4 multimode fibre , 100 gigabit speeds require the use of eight fibres via the 100GBASE-SR4 application ( four fibres transmitting at 25Gb / s and four receiving at 25Gb / s ). In contrast and as shown in Figure 1 , using the single-lane 25Gb / s application 25GBASE-SR with WDM technology , OM5 fibre links could potentially support 100Gb / s using just two fibres ( four different wavelengths on one fibre transmitting at 25Gb / s on and four different wavelengths on one fibre receiving at 25Gb / s on ).
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Similarly , using 100GBASE-SR4 specifications , 400 gigabit OM5 fibre links could be created using 8-fibre MPO / MTPs transmitting and receiving at 100 Gb / s over four different wavelengths .
While OM5 may seem like an advantage in terms of reducing fibre strand counts , it is important to note that there are no applications currently under development within the Institute of Electrical and Electronics Engineers ( IEEE ) to operate over this medium and , as a result , there is no available information on data rate , link length , or strand count for installing this media today . In addition , because IEEE typically develops applications based on a significant installed base , it is not certain when and if any application will be developed . Further , OM5 carries a significant cost premium over OM4 , and a premium will also apply to any future transmission equipment . As such , one of the emerging singlemode fibre applications may be the better solution for anyone looking to future proof for 400 Gigabit . For example , the pending IEEE P802.3bs ( 400GBASE- DR4 ) standard is slated to cost effectively support 400Gb / s over singlemode to 500m using 8-fibre MPO / MTP solutions with four fibres transmitting at 100Gb / s and four receiving at 100Gb / s .
In addition , the pending IEEE P802.3cd ( 50GBASE-SR ) standard – anticipated to release in 2018 – will support single lane 50Gb / s , demonstrating IEEE ’ s commitment to the development of higher capacity applications over the
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Figure 1 : 25GBASE- SR with WDM technology over OM5 fibre links can support 100Gb / s using just two fibres |
installed base of OM3 and OM4 multimode fibre . There is also work on singlemode technologies for shorter reach ( 500m ) applications via the pending IEEE P802.3cd ( 100GBASE-DR ) and IEEE P802.3bs ( 200GBASE- DR4 / 400GBASE-DR4 ) that may provide yet another case for singlemode fibre to be considered .
All channels point to 2 and 8
In looking at current and future applications – for both multimode and singlemode – it is easy to see that the foreseeable future
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