Dark Fiber what is it? How is it priced and how different is it from ‘traditional’ internet connectivity?


Dark Fiber what is it? How is it priced and how different is it from ‘traditional’ internet connectivity?

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Dark fiber is fiber that has not been put into service, i.e. “lit”, by a service provider. It can be leased from the service provider that owns it, but it is up to the customer to provide the equipment to put it into service.

Dark fiber is a fiber optic line which have been patched through between two places without any equipment “lighting” the strands of the fiber. The term is currently often used for a number of different technologies which do actually have some sort of equipment such as light amplifiers, multiplexer prisms, etc. But the general idea is that the customer have to provide the equipment in the ends of the fiber and can use the fiber for whatever they want. So it does not have to be for network and does not have to be within any specification.

Dark fiber is typically used by a company to connect different server rooms and data centers within a city to each other. If you have dark fiber between two locations you can be guaranteed full speed, isolation from other networks and can do things like increased MTU, fully encrypted data streams or even quantum encryption. The ISP does not even see any of the data.

The difference between dark fiber and Internet connectivity is that dark fiber is not connected to the Internet, it is just connected to two different locations of yours. The ISP is just providing the physical infrastructure and nothing else. That being said it is not that uncommon to buy dark fiber from a data center or similar to a local Internet Exchange where there are lots of ISPs present. The Internet connectivity is cheaper because you are paying someone else for the infrastructure but overall this tends to be more expensive. So it is possible to get Internet through dark fiber in this roundabout way. There are also cheaper options for links then dark fiber where the ISP use their existing switching network for parts of the link. But then you are limited in what you can send over the link.

It’s just unused fibre, essentially a spare cable, you can plug into.

You might get multiple hops (e.g. from one office to a central location, and then back out to another office). You might also rent space for equipment along the way (e.g. you might get dark fibre to a central location, owned by the same/a different provider, from several places you own, then put some routing equipment in the central location).

For example, I work at a place that has dark fibre from various offices to central locations in each city. Then we rent leased lines (on a fibre used by other people as well) between cities.

Pricing is kind of wild. Depends massively on the route, how much competition, alternatives etc.

Getting dark fibre out of an office building to a data center can be quite reasonable. Unless, say, the office needs the fibre installed (e.g. it only passes by as is) and the provider has a monopoly on dark fibre into that data center, then it can be absurdly expensive.