Assessing the differences between multimode and singlemode fibre

04 January 2018

Alastair Waite, data centre solution architect, EMEA, CommScope

Alastair Waite, data centre solution architect, EMEA, CommScope

Recent predictions say there will be a 25 to 35 per cent annual growth in data traffic. This is putting data centre managers under increasing pressure to evolve to provide higher capacity across almost every type of network.

To facilitate this growth, many have begun to use fibre optic cables and transceivers to such an extent that fibre is now the trend in many data centres.

With the need to provide higher capacity, the design of data centres that can deliver this at an optimal cost is also changing. One of the hot discussions to emerge from this is around the type of fibre to deploy: singlemode or multimode. 

The fashionable answer may be to deploy singlemode, as used by long-haul telecoms networks. However, if multimode can also deliver high capacity with distance support, there are reasons to consider continuing with its use. 

Here are a few of the issues that should be considered when weighing up the options: 

Support for distances: lower cost multimode may be more attractive, but only if it can support the speeds that will be required as the network evolves.

Singlemode, on the other hand, is commonly used in data centre entrance facilities and its long-distance capabilities make it the only choice for links between the centre and MANs/WANs. In fact, many long-reach, high-speed options are only available in singlemode.

Costs: comparing these between network types involves assessing the cost of the entire link – transceivers, trunks and patch cords. While the outlay for any link is length-dependent, some have an inherently higher cost due to an increased number of fibres. Therefore, knowing the link length enables you to determine the lower-cost solution. When the average channel length is known, making an accurate comparison between link types becomes easier.

Network topology: some data centres may have more than 100,000 servers while others may have just a few. Some use a centralised placement of network equipment while others distribute networking equipment throughout the data centres. These design requirements and choices determine the number of network links and the distance those links must support.

Considering these factors will ensure a cabling solution that is easy to maintain as well as scale as you grow in line with rising data demands.