Dark Fibre vs Lit Fibre

There is a lot of conversation about fibre –  but what exactly is the difference between dark fibre and lit fibre, and which one is right for you?

There are several pros and cons for choosing either Dark Fibre vs Lit Fibre.

Dark Fibre is simply a length of fibre optic cable which has no equipment connected to it and is not transmitting any data. A business will lease or buy this fibre from a network provider and then fully manage the equipment, deployment, security, traffic and maintenance themselves.

In contrast to this choosing a ‘lit’ option puts the onus on the network provider who will then be responsible for keeping the fibre lit and ensuring availability and capacity. Lit services like Ethernet, Optical Wavelengths of Optical services most often come with a Service Level Agreement (SLA) which promises the business a certain level of availability and support – up to 99.99%. Capacity across lit fibre can scale from 1Gbps to 100Gpbs with even some high-speed 200Gbps across either standard or dedicated wavelengths.

Dark Fibre capacity is limitless and is easily scalable. As the whole fibre is leased by and dedicated entirely to that business, it means they use the capacity how they choose. That includes taking advantage of technology like Dense Wave Multiplex Divisioning (DWDM) where equipment at the end of the fibre can split the light out in to the various wavelengths of the spectrum to carry data and increasing capacity significantly – up to 400Gbps across a single fibre using 80 channels.

Whilst lit fibre lacks the ability to easily and quickly scale, the timescales of getting Dark Fibre set up are much longer and more costly.

With Dark Fibre, businesses are themselves responsible for leasing the fibre as well as buying and maintaining the equipment and the IT staff needed to use the fibre. For lit fibre any downtime would be the issue of the carrier but can be a bit more restrictive in terms of routes as the fibre is already laid and connectivity to the premises depends on whether the network provider’s route runs there.

Dark Fibre and Lit Fibre offer businesses very different options, so it is important to consider what is most important to your business – whether that is cost, diverse routing, dedicated bandwidth and the kind of levels of capacity and whether it will need scaling in the future.

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