data centres
over multimode optical fibre cabling, longer distance transmission via WDM and LAN WDM over single mode optical fibre, and extremely short distances via multiple lanes of parallel coaxial copper cabling.
In practical terms within the data centre, the demand for increased bandwidth as 40 and 100 Gigabit become more prevalent means that transmission distances over existing fibre optic cabling infrastructure could well become more limited over time. Higher bandwidth requirements have, thus far, required the transition from multimode systems to single mode systems – with the likelihood of significantly increased costs. The development of the OM4 laser optimised, high bandwidth 50µm multimode fibre promises an additional performance layer, supporting faster speeds at longer distances, and, therefore, limiting the number of installations that require single mode fibre. OM4 has the capability of reaching 150m and supporting the vast majority of links required within the data centre. Several recent studies have shown that total link cost for 40 Gigabit Ethernet systems using the OM4 multimode system are one third of those using single mode cabling. For 100 Gigabit Ethernet, single mode can cost almost 10 times more than a multimode system. Single mode CWDM has a lower cabling cost, but a significantly higher transceiver cost when compared to OM3 and OM4 multimode parallel systems – which might have higher cabling costs, but much lower transceiver cost, using existing 10Gb/s VCSELS.
It’s time for OM4 Clearly, potential cost savings and longer distances are attractive starting points when discussing the benefits of OM technology, but there are significant other benefits.
OM4 is backwards compatible with existing OM3 systems – a not inconsiderable plus when one considers that some networking technologies do require a rip and replace approach to implementation. In terms of energy efficiency – increasingly important as link density and speed increase – there are further savings to be made. The 10G SFP+ fibre transceivers used as part of the OM4 multimode system offer potential energy savings of 9W per transceiver, and that’s 9W per transceiver less cooling required as well.
special feature
Strategic decision Strategic cable management is becoming an increasingly important issue within the data centre and OM4, used as part of a properly planned cable management strategy, offers the possibility of reducing and, therefore, simplifying, the number of paths and cables required. On the downside, 40 and 100 Gigabit Ethernet over multimode optical fibre will require a significant increase in the amount of optical fibre than is currently used for 10 Gigabit Ethernet – up to four times more for 40 Gigabit Ethernet and 10 times more for 100 Gigabit Ethernet. The management of optical fibre density is a key consideration moving forward. For example, managing and routing optical fibre cables in and above racks.
As a result, cabling needs should be considered independent from its short term use and made part of long term infrastructure planning, with the following benefits:
Reduction in operative costs. Shorter downtime during moves/adds/ changes (MACs). Improved reliability.
Reduced risk of unintended breakdowns.
Alongside the emergence of the OM4 standard, bend insensitive fibres have been developed to offer reduced size cable cabinets – reducing ownership costs, and looking to alleviate the pressure that massive optical cabling requirements put on installation practices, with the inherent chance of increasing bending loss. Recent studies have shown that in links having three to five joints – which is not unusual in data centres – the optical energy within the MM fibre also launches into higher order modes, which are highly affected by bending. The fact that certain lasers don’t launch all fibre modes in the
beginning doesn’t protect the link against accidental loss increase.
In particular BI-MM fibres allow small form factor designs in cable and connectivity, which enable the required transmission capacity along with significantly increased packing density. It should be put in perspective, that the next generation of Ethernet requires at least four times the number of fibres, but in practice room availability for this tends to be lower rather than higher. Implementation of bend insensitive fibre technology can provide multiple benefits, including increased spare system margin that improves 10G and up network reliability, increased flexibility thanks to option using sub-distributors, better suited for MACs, and the possibility of new, reduced size cable designs that are lighter in weight, have improved cooling efficiency, and have a reduced environmental footprint – supporting the development of greener data centres.
Carsten Fehr is marketing manager, responsible for the EMEA marketing and business development of Draka’s Datacom business which is a part of Draka Communications.
Carsten’s responsibility within Draka is centred on the optimisation, development and implementation of business models in data communications together with concepts for emerging
applications with a focus on fibre optics and next generation data communications infrastructures.
Carsten Fehr has 13 years of experience in product management as well as six years in R&D management, working with global vendors in the telecommunications industry.
27
The data centre’s core network needs to be capable of supporting much higher traffic speeds.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52