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Will 400Gbps ever be relevant to Africa?

31 May, 2013
ICT Africa
May 31, 2013

The lingering perception of Africa as a continent of famine and wars has always resulted in a gross underestimation of the demand for ICT services in Africa. Most people who have attempted any long term forecast of ICT services and bandwidth requirements in Africa have always gotten it wrong. Perhaps the trickiest thing to predict has been future transmission rate requirements in African backbone networks.

I remember talking to some people in the telecommunication industry in Africa some ten years ago about what was needed to prepare for the adaption of 10 Gbps line rates in the long haul network. Somebody remarked that “Africa was not America” and that such high data rates were not going to be required in Africa. At the time, most of the African operators deploying backbone networks were deploying SMT-4s (or 622Mbps) or 2.5 Gbps. Today, almost every African operator deploying a new backbone network is deploying 10Gbps.

Only three years ago, I was discussing 100Gbps with a representative of an incumbent telecommunication operator in North Africa. He thought 100Gbps was too futuristic and that it was going to take a life time for anyone to implement it. I was very excited to meet him again this year and updated him on the fact that a number of operators throughout the world, including in Angola, were deploying commercial 100Gbps. I also told him to look out for 400Gbps in the not too distant future.

Perhaps we should all look at the evolution of international standards for transmission rates to get a better indication of likely future transmission rates. Today 40Gbps and 100Gbps are standardised and the standards organisations are working on 400Gbps. Prototypes for 400Gbps have already been showcased at the Optical Fibre Conference (OFC) in Anaheim, California, in March 2013. We expect commercial availability of 400Gbps systems by the 2014-2015 timeframe and for early adapters to deploy these systems by the 2017 timeframe.

Given everything we know now; history of line rates in Africa, rapid deployment of mobile networks, deployment of high bandwidth mobile technologies such as LTE, video streaming on mobile handsets, initial deployment of FTTH in Africa and the utilisation of many bandwidth hungry applications; there is no need to believe that 400Gbps will not be relevant to Africa. 100Gbps is already being deployed in Africa and I can bet that in ten years’ time there will be widespread deployment of 100Gbps and early adapters will start to deploy 400Gbps thereafter.

The question we get asked a lot is why the need to move to extremely high data rates when multiple channels can be transmitted in a single fibre pair using DWDM (Dense Wavelength Division Multiplexing) technology. While the operating wavelength band of standard single mode fibre is extremely wide, from about 1260nm to about 1625nm (in excess of 360nm), the erbium doped fibre amplifiers (EDFAs) used to boost signals in long haul transmission systems have a limited bandwidth of about 40nm. The most cost effective EDFAs to make operate in the C-band, between 1530 and 1570nm. Most DWDM systems made today operate in this band at central wavelengths specified by the so called ITU Grid. The spacing between channels is typically 100GHz (0.8nm) giving 50 channels or 50GHz (0.4nm) giving 100 channels.

In practice the components used to generate all these channels have their own limitations. Typical systems are capable of 64 channels at 50GHz spacing and 32 channels at 100GHz spacing so that you are practically limited to 64 channels or 640Gbps if you are transmitting at 10Gbps per channel. For large operators in developed countries; Verizon, AT&T, NTT, BT, Deutsche Telekom, etc.; this falls far too short for their requirements and hence the need to migrate to higher data rates per channel. When more and more operators migrate to 100Gbps, the cost of 100Gbps systems will go down. If you ever needed up to 100Gbps of transmission capacity in the future, it will be less expensive to buy one 100Gbps line card than to buy ten 10Gbps line cards. The same argument holds for 400Gbps.

We are also asked the question about whether existing fibre will work with 100Gbps and 400Gbps but we will defer that discussion to a future ICT Africa article to keep the size of this article manageable.


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