Dark Fibre

What is Dark Fibre?

The term “Dark fibre” refers to cables that have spare fibres inside that have no equipment at connected. Any fibre requires optical equipment connected to it before it can be used, using light signals to pass signals from end to end (hence the term ‘optical’ Fibre). So if a fibre is presently unused it is said to be “dark”.

Dark Fibre Networking

Organisations that are able access Dark Fibre connections between their premises are able to connect their own equipment to it. Thus at that point the fibre will cease to be ‘Dark’ and will in fact be ‘Lit’! However unlike a normal leased line or FTTP connection from an ISP or Service Provider, the whole fibre is dedicated to you.

Dark fibre isn’t shared with other users but is dedicated to the organisation so it can offer significantly higher capacity and lower latency than typical broadband or leased line connections.As far as the actual fibre owner is concerned the fibre remains ‘Dark’ since their equipment is not used, and their responsibility stops beyond making sure that it is properly connected.

So in ‘Dark Fibre’ Networks, the equipment used to ‘light’ up the fibre is your choice and your responsibility – and with that choice you can do a lot more, with very compelling business propositions beyond the alternatives from Service Provider services.

Business Services based on Dark Fibre Networks

Fibre based services require an end to end connection between locations. Using that fibre,organisations can create any kind of connectivity service with bandwidths from as low as a few kilobits per second through to fairly typical Gigabit connections to 10s or even 100s of gigabits – all using the very same fibre. The only difference is the equipment on the end!

Versus Leased Line or FTTP services: As organisations grow, they often require more and more bandwidth. Thus organisations feel compelled to increase their bandwidth or service level, or to add new services that offer alternative characteristics such as latency, security, availability or protocol support. But this can become an expensive endeavour once these multiple or high bandwidth services are added.

The cost of Dark fibre based network connectivity services using equipment that is owned by the organisation scales differently, because the fibre itself remains the same. When new or different network services are added, only the equipment needs to be upgraded and once that has been done it is yours!

Wavelength Division Multiplexing (WDM)

At a Glance: Wavelength division multiplexing (WDM) expands fibre capacity by use of different colours of light operating on one fibre pair. Each colour operates independently as if it were an individual fibre in its own right and each can support network connections operating from the kilobit range to the 100Gigagbit range. This has a clear financial incentive as improving the equipment at the ends of fibre cables is drastically more cost-effective than placing more fibre in the ground. At Sorrento we use the term Virtual Fibre for this.

This is just one example of how to use fibre to improve the efficiency of your network. There aremany others. More information can be found on our Guide to Wavelength Division Multiplexing.