When Does Dark Fiber Make Sense?

Dark Fiber is an appealing WAN option for many enterprises due to its high bandwidth capabilities. But when does utilizing dark fiber actually make sense?

dark fiber
Ginger Woolridge

Nov 12, 2021


Corporations have different business models and networking needs. To support the functionality of complex and data heavy applications, one thing is for sure - you will require a significant amount of network bandwidth and control over your network.

In such cases, dark fiber - a high capacity, customer managed communication line - becomes an appealing Wide Area Network (WAN) option.

What is Dark Fiber?

Dark fiber, which also goes by the terms “unlit fiber” and “black fiber”, is fiber optical cabling that a telecommunications service provider has laid but does not use.

They often sell the lines to other carriers, like AT&T and Comcast, but sometimes also to enterprises in need of high bandwidth connections. The businesses light up the cabling by deploying network equipment on both ends of the line and establish their own high speed, private network.

Such deployments represent a significant and growing portion of the WAN market. The global dark fiber network market accounted for $5.16 billion in revenue in 2020 and is expected to reach $10.51 billion in 2028, a Compound Annual Growth Rate (CAGR) of 9.3%.

When Does it Make Sense to Deploy Dark Fiber?

High Bandwidth Requirements

‍Companies with high bandwidth needs (often 100G bps or more of capacity) are prime candidates for dark fiber. With dark fiber, enterprises can scale their network applications far beyond the bandwidth capabilities that even lit fiber usually offers.

Dark Fiber is a dedicated WAN service, so only one company uses the transmission line or “strand” in question. Consequently, they are ensured that their data travels from its start to its destination without being interrupted by someone else’s traffic.

And with this, your cost does not scale with your data usage. Instead of paying more when using more data (the payment structure of most ISPs with lit fiber, also known as burstable bandwidth), a dark fiber network offers economies of scale with a fixed payment for unlimited data usage.

It’s worth noting that a single strand of dark fiber can now transmit up to 800 Gbps of data. So, if your company’s bandwidth requirements are significantly lower than that and you don’t plan to scale your network needs anytime soon, dark fiber might not be worth it for you.

You are comfortable purchasing and managing the optics on both ends

When utilizing dark fiber, the user is entirely in charge of purchasing and managing fiber optic equipment used to “light up” the dark fiber.

These electronics are expensive and can be complex to maintain. The customer must furnish all network gear at each point-of-presence (POP) from Add-Drop multiplexers to optical regenerators, which boost the line’s light intensity and eliminate signal attenuation along the fiber route.

You are comfortable with owning responsibility for fully managing, supporting, configuring and troubleshooting the link.

With dark fiber, your IT team is entirely responsible for managing, configuring, supporting, and troubleshooting the connection.

Deploying and maintaining a dark fiber network can be a challenging endeavor. The process requires highly trained and skilled personnel to implement and maintain the equipment, skills that many companies’ staffs lack.

When Tight Security & Uptime Standards are Required

Your network security is enhanced when utilizing dark fiber. Since it is a private network, dark fiber is not susceptible to the ruses hackers use to gain access to others’ computer systems on shared networks. The customer is also able to deploy whatever cybersecurity solutions they are comfortable with to ensure safe data transmission.

Additionally, you can expect improved network uptime when utilizing dark fiber. With dark fiber, your company data is segregated from the public Internet, and even the carrier’s core network backbone. Consequently if the carrier has an outage, the dark fiber connections are not impacted. The customer determines how much redundancy to put into the network design, so it creates availability measures that meet their business demands.

Dark Fiber Downsides

But dark fiber is not a panacea. The service fits only with companies with significant bandwidth needs and select use cases, such as Disaster Recovery as a Service (DRaaS) and large file transfers.

Additionally, dark fiber strands are often leased in longer terms (three to 20 years) than their lit fiber counterparts (two to five years). Read more about the dark fiber long term commitment here: Indefeasible Right of Use (IRU) leases.

Finally, dark fiber is not as widely available as other telecommunications services. When searching for dark fiber service, one must keep in mind that just because a telecommunications services company has a dark fiber line nearby, it does not mean that they will lease it to you. As with all wireline technologies, the "last mile" to termination is always the trickiest to work out. Some areas, especially more remote locations lack ready access to a nearby dark fiber network.

Dark Fiber Pricing

Dark fiber is often charged by the “strand” and cost will vary based on the distance of the connection.

We have seen one provider price two strands within the same city for $650 MRC, and we have also seen carriers charge thousands for similar lengths.

Check out this report for our full analysis on dark fiber pricing.

The Next Step

Dark fiber is a popular option for companies that need high bandwidth, private network connections. However, the level of IT sophistication needed to select, deploy, and maintain these lines extends beyond many organizations’ capabilities.

So when trying to determine if this network option meshes with your communications needs, you may need input from a telecom expert. Many Lightyear customers have successfully deployed dark fiber and other high speed network options.

To get started, you can utilize Lightyear’s 2-minute online questionnaire to configure your dark fiber needs and source quotes. If you aren’t sure about dark fiber, schedule a demo today for more information about how Lightyear can help you in the dark fiber evaluation process.

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