Fibre optic networks are becoming the transmission medium of choice in today’s networks. The traditional copper-based cabling is on the way to not supporting the high-bandwidth requirements of multi-media sites. Coupled with its life span of about 10 to 15 years, many copper-based UTP installations are needing to be replaced or upgraded.
A further motivator is that the limited length of cables, currently around 90-95 metres means additional expense in networking equipment like cabinets and switches. The use of Passive Optical Lan cabling in buildings overcomes distance limitations and is increasingly being used when copper cabling needs to be upgraded or replaced.
We often hear the phrase “Dark Fibre” casually used in cabling circles. What does it mean, and why should you consider using it?
Dark Fibre
The simplest definition of dark fibre is optical fibre that has been laid but is not currently in use. It may also refer to a blown fibre environment where the fibre tubes are not populated. There are currently large amounts of dark fibre in the US and Europe, laid but not used. The term arises because when active optical fibre carries light, but unused fibre doesn’t. Hence active fibre is lit, and unused fibre is dark.
The collapse of the dotcom bubble has resulted in the existence of large amounts of dark fibre. Organisations, particularly Telcos, installed lots of fibre in the expectation that the growing dotcom economy would need it. When the bubble burst, it was in the ground, and just stayed dark.
Technical advances like wavelength-division multiplexing, allowing larger volumes of data to be carried on existing cables further reduced the demand for additional fibre.
The cabling companies who installed dark fibre want to make money from it, so they lease it to companies and individuals for their own use. This can make financial and timing sense for both parties.
A major cost in creating a network is the cost of laying the network cabling and the cables themselves. Most budgets show that the cost of creating the physical network is much higher than the cost of the cables themselves. Many ancillary costs are associated with network installations, trenching, creating ducts, channels and manholes, and finally the installation costs themselves.
Laying fibre over long distances can be very time consuming and expensive. It is almost always more cost effective to lease existing dark fibre than lay more fibre of your own.
In recent years the use of blown fibre to allow new fibre to be installed at a later stage without the need for trenching has saved both time and cost when networks need to be extended. It also provides benefits in reducing maintenance time if cables need to be replaced. Blown fibre uses tubes that will contain the fibre cabling. When they are used, a device like a large hair-dryer literally blows the fibre cabling along the tubes to the destination. This is a lot cheaper than installing new cable in trenches and saves significant time in setting up new networks or extending existing ones.
Why You Should Use It
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Connectivity
Fibre provides high-capacity, high-speed point to point connectivity that supports the high-bandwidth applications in today’s multi-media environments.
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Scalable
Using leased dark fibre can provide a fibre environment that grows with your business. It can be cheaper, requiring less capital expenditure. You can create your own private network without needing to lay your own fibre. As a result, it can be brought into operation more quickly.
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Coverage
In the US there is plenty of dark fibre in most major metropolitan centres, and often between them as well. Your network can be configured to quickly expand to provide regional and national coverage.
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Control
It’s your network, so you control how it is to be used, the end-point equipment and how and when it is to be deployed and managed.
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Security
You have your own fibre, separate from anyone else’s. It’s your own private network.
The availability of dark fibre to individuals makes good financial and operational sense. It transfers cost from capital expenditure to operational expenditure. It reduces the time to bring a network or network extension into operation because the fibre already exists. Overall, it’s a boon.
