FACILITIES ca bling
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http://www.dcseurope.info/n/hnhb
Beating the specification: looking beyond
FTTH
Joost Grillaert, Fibre Product Manager Nexans Cabling Solutions, explores the impact of reach capabilities for 40G Ethernet over multimode fibre.
WHILST TRAFFIC INCREASES as a result of the greater capacity offered by FTTH, the supporting infrastructure also requires an upgrade to higher speeds. First of all, data centres that handle FTTH traffic must be enabled to handle these higher volumes. To achieve that, migration to 40G is required. Although many data centre operators are wondering whether they shouldn’t jump straight to 100G, 40G seems to be the first step for mainstream data centres, as more efficient solutions for 100G are being developed.*
Most switch suppliers are currently already offering 40G solutions. However, migrating to 40G isn’t as easy as it may seem. Ever since the 40G standard was approved in 2010, data centre owners and installers have been expressing their concerns about one specific drawback: the limited operational distances as described in the specification. The relatively short distance offered by the 40G standard using multimode fibre has a number of consequences for data centre and FTTH network design, as more complex configurations are simply not possible. For existing data centres this could even mean a redesign is in order, as channel lengths are decreased and the number of cross connects is limited.
Data centres are often split across different rooms within a single building, either by design or simply because the building’s architecture dictates a specific layout. Sometimes, the SAN isn’t located in the server room. In other cases, a data centre might be located in multiple adjacent buildings. The required cabling distances
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www.dcseurope.info I November 2013
really add up very quickly. There is, however, hope: in practice new networking products will be able to potentially solve any problems imposed by increased distances. As a consequence, installers might not be as limited by the new standard as originally believed...
Quadruple distance
The 40G specification guarantees effective data transport up to a distance of 150 metres. However, tests carried out at Nexans Data Communications Competence Centre (DCCC) in the USA, show that far greater distances - in excess of 600 metres - can be realised using pre-terminated fibre assemblies with 9 MPO connectors. That’s more than four times the reach, with more than four times the connectors specified by the IEEE. During the 100G frame testing with a 7-connector channel, a distance reach of 500 metres was successfully achieved. The performance boundaries of pre-terminated optical fibre assemblies were extensively tested using a variety of configurations and platforms. To make sure test results were relevant to real world applications, multiple connection points were used to test the links between switches.
To summarise: the recent test results demonstrate that high-quality enhanced OM3 and OM4 cables consistently exceed the IEEE Standard for both 40G and 100G Ethernet by a substantial margin. The DCCC results are particularly noteworthy, not only for the distances achieved, but also due to the utilisation of frame error rate
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