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What is Dark Fibre and What are the Benefits?

What is Dark Fibre and What are the Benefits?

What is Dark Fibre?

Modern internet traffic is carried by miles and miles of fast fibre optic cabling that’s been laid in the ground. However, not all of that fibre optic cabling is being utilised.

In its most basic form, fibre optic cabling is a glass conductor between a transmitter (laser beam) and a receiver. The electronic signals are changed to pulses of light for the laser to transmit, the receiver then collects these pulses of light and converts them back into electronic signals.

The unused cores, which have no electronic devices attached at either end, have been given the name dark fibre in reference to its ‘unlit’ state.

What are the benefits of Dark Fibre?

Disaster Recovery

Every network engineer’s worst nightmare is the loss of connectivity of a fibre optic link. Whilst spare SFP’s (Small Form-Factor Pluggable) and patch leads can be found in almost all server rooms, spare fibre link cables are more of a rarity.

There are specialist companies that will come out on a call out basis should a cable get damaged, either through an accident or rodent/animal damage. However, this may still take several hours to complete. Where dark fibres are installed, they can easily be swapped over to allow for repair works to be carried out without the rush.

Potential Cost Savings

If your organisation has an issue with a damaged cable that is stopping network connectivity to a key part of your business and emergency repair is required, you may find yourselves at the mercy of whoever can get to you the quickest.

Having the ability to move to pre-installed dark cabling will allow you to obtain quotations to carry out the works in the best and most cost-effective manner without time restraints.

What are the Drawbacks of Dark Fibre?

Will it Work?

The main drawback of dark fibre is that it will sometimes present a false sense of security. If a lit fibre should become damaged, your network connectivity will alert you to it. However, there is no such system for dark fibre and if it were to become damaged, in all probability the first time you would know about it would be at the point when you need it the most. This can be minimised with regular testing, inspection and verification of these dark links.


Any network engineer who has experienced a cable related outage, will agree that a dark fibre is an asset to any network infrastructure. Network downtime can be a huge problem, therefore, processes to minimise the potential disruption are very important.

Remark Group have the experience and knowledge to advise you on the best structured cabling solution for you. Get in touch today to discuss your needs further.

Written by our Project Manager, Jonathan Dolby. Jonathan has 13 years of experience in network infrastructure and specialises in structured cabling.

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