Dark Fibre vs Carrier-Neutral Interconnection: What Buyers Need

Two different answers to the same question

Once your equipment is in a data centre, it needs to reach the outside world: offices, a second site, cloud platforms, partners and the internet. Two terms come up early in those conversations: dark fibre and carrier-neutral interconnection. They solve different problems.

Dark fibre is about owning the path. You lease raw fibre between two points and run your own equipment over it. Carrier-neutral interconnection is about choice. You place your equipment in a facility where many networks are present and connect to the ones you need. Most businesses end up using carrier-neutral interconnection, and some add dark fibre for specific links. This guide explains both, the trade-offs, and how to decide.

What dark fibre is

Dark fibre is optical fibre that is installed but not "lit" by the provider. You lease a fibre pair between an A end and a B end, and you supply the optics and network equipment that send light down it. The provider looks after the glass and the route. You decide the speed, the protocol and how the link is managed.

Australian providers describe it in similar terms. Telstra's dark fibre terms describe the service as a pair of unlit single-mode fibres between two sites, with the customer responsible for its own equipment and patch cords. NEXTDC's metro interconnect fibre service provides a pair of unmanaged fibre cores between its data centres in the same city, with the customer supplying optics and setting the capacity.

Dark fibre is different from a managed wavelength or a managed Ethernet service. With those, the carrier lights the fibre and sells you a defined amount of bandwidth with a service level agreement. Dense wavelength division multiplexing (DWDM) lets many wavelengths share one fibre, which is why managed wavelengths are often more practical over long distances.

Dark fibre suits organisations that:

• Need very high or growing capacity between two fixed points, such as a primary and secondary data centre in the same city.

• Want full control over equipment, encryption and upgrade timing.

• Have the network skills to design, monitor and troubleshoot an optical link.

What carrier-neutral interconnection means

A carrier-neutral data centre is one that is not tied to a single telecommunications carrier. Many carriers, internet providers, cloud on-ramps and internet exchanges can establish a presence in the building, and customers connect to them with cross-connects through a meet-me room.

The value is choice and competition. In a facility with many networks on site, you can compare offers, buy from more than one carrier for diversity, and switch providers at contract renewal without moving your equipment. You can also reach cloud platforms and partners directly inside the building, as explained in our connectivity choices guide.

Being carrier-neutral does not guarantee that every network is present in every building. Lists of on-net providers vary by site and change over time, so always confirm the exact networks in the facility you are considering. The provider directory and compare tool are a good starting point.

Cost and control trade-offs

Dark fibre and carrier-neutral services shift cost and responsibility in different ways:

• Up-front costs. Dark fibre usually involves build or connection charges and your own optical equipment. Lit services from a carrier mostly bundle the equipment into a monthly fee.

• Ongoing costs. Dark fibre is typically priced per route rather than per megabit, so adding capacity can mean upgrading optics rather than paying more each month. Lit services are usually priced by bandwidth and term.

• Control. With dark fibre you choose the equipment, encryption and upgrade path. With lit services, the carrier manages the transmission layer and you rely on its service levels.

• Responsibility. With dark fibre, your team owns more of the fault-finding. With lit services, the carrier monitors the link and handles much of the restoration.

• Contract terms. Dark fibre is often sold on longer terms because the provider may need to build or reserve the route.

Prices vary widely by route, provider and term, so get written quotes for each option rather than relying on rules of thumb. Our colocation cost guide explains how connectivity fits into total cost.

Resilience: one fibre pair is not redundancy

A single dark fibre pair is a single path. Telstra's terms state that each dark fibre service is non-diverse unless specifically agreed, and that it does not monitor or maintain diversity after delivery. NEXTDC's guidance for its metro fibre service notes that faults in street fibre, such as during road works, are more likely than faults inside the data centre and can take considerably longer to fix, and recommends considering a second path.

For critical links, plan for:

• Two fibre pairs on physically separate routes, with separate building entries.

• A lit service or internet path as a backup if a second fibre route is not available.

• Written route information, so you know where paths share trenches, ducts or bridges.

Our guides on Sydney–Melbourne fibre and geographic redundancy cover longer routes.

A note on regulation

If you lease dark fibre from a licensed carrier for your own use, the carrier owns the network. Organisations that build or own fibre themselves should check their obligations. The Australian Communications and Media Authority (ACMA) explains that under the Telecommunications Act 1997, the owner of a network unit used to supply carriage services to the public generally needs a carrier licence, unless a nominated carrier declaration or an exemption applies. Use within the owner's "immediate circle", such as its employees and related companies, is generally not treated as supply to the public. Get advice if your plans involve owning fibre or supplying services to others.

When to choose each

Carrier-neutral interconnection is usually the better starting point when you need internet access, cloud connectivity, several carriers for diversity or flexibility to change providers. Dark fibre becomes attractive when you have a stable, high-capacity link between two fixed sites, the skills to run it, and a reason to want full control.

Many organisations use both. A common pattern is a primary site and a secondary site in carrier-neutral facilities in the same city, joined by dark fibre, with internet and cloud services bought through cross-connects in each building. Compare options in your city on our Sydney, Melbourne and Brisbane pages.

Questions to ask before you sign

• Which carriers, internet exchanges and cloud on-ramps are present in this exact building today?

• For dark fibre, what is the route length and expected optical loss, and which optics are supported?

• Is the fibre route diverse from my other paths, and will you tell me if it changes?

• Who is responsible for fault-finding, and what are the repair commitments?

• What are the cross-connect fees at each end, and how long do they take to deliver?

DChunt is independent and does not resell data centre space or network services. Our free assessment can help you match connectivity needs to the right facilities.