The Dark Side of Fiber: Pros and Cons of Dark Fiber

Dark fiber networks can help enterprises scale network applications and improve performance and security. Consider dark fiber with our pros and cons guide.

dark fiber meme 2
Ginger Woolridge

Nov 11, 2021


Cover Photo Source: BBC

Just like the color of your lightsaber defines what type of Jedi you are, whether the fiber optic cable you are procuring is lit or not determines the capabilities and quality of your network connectivity. "Lit" fiber, which looks like strands of glass pulsating with light, is actively in use and transporting data. But dark fiber, or wholesale fiber, refers to unlit fiber optic cable that is not carrying traffic - and is potentially the answer to your networking needs.

“If Only You Knew The Power Of The Dark Side...” - The Empire Strikes Back

We've discusseddark fiber before. By harnessing dormant fiber cable, enterprise-level businesses can scale their network applications far beyond the bandwidth capabilities that twisted-pair copper or coax or even lit fiber offers. Yet, deploying and operating lightwave networks can be costly and requires highly trained and skilled personnel to implement.

Is leasing dark fiber right for your business? Managing a fiber network only makes sense for organizations needing the firepower of a dedicated optical network: some examples include very high capacity interconnections between multiple sites, data centers for real-time replication, and large data transfers. While dark fiber can be cost-effective, its value often lies in applications requiring >10 Gbps of throughput, specific routing, and/or very low latency.

Consider the following pros and cons of dark fiber networks before taking the leap:

1. Dark fiber is not as available as lit fiber services such as Wide Area Ethernet or point to point solutions.

While every office building has twisted-pair copper, coaxial or lit fiber wiring, simplifying the deployment of Ethernet solutions, some locations may lack ready access to a nearby dark fiber network. As with all wireline technologies, the "last mile" to termination is always the trickiest to work out.

What’s more, unlike lit fiber services, dark fiber is often a product that is available only to the wholesale market or, in the case of companies like AT&T and Comcast - not available at all. When searching for dark fiber it is important to keep in mind that just because a company has a fiber network nearby, it does not mean that they will lease you dark fiber. However, some examples of “friendly” dark fiber providers with extensive networks who will sell dark services to both commercial and wholesale channels are Zayo and Crown Castle.

2. International Private Leased Circuit (IPLC) or Indefeasible Right of Use (IRU) Lease?

Providers may offer fiber connections to enterprise customers through either an IPLC, for international circuits, or IRU lease. Contrasts between IPLC and IRU leases include:

  • Borrowing from the business fable of the chicken and the pig opening a restaurant, the chicken is involved with an IPLC but the pig commits to an IRU. An IPLC lease may be month-to-month or last 2-5 years. Conversely, an IRU lease is an absolute betrothal to lightwave networking. Once signed, a lease with an IRU clause cannot be voided or unmade and generally lasts for the service life of the fiber network (viz., 25-30 years).

  • An IRU is paid upfront in addition to monthly recurring fees and allows the customer to lease bandwidth capacity to network "subletters." This subletting option is typically unavailable with IPLC contracts. IPLC leases are not pre-paid contracts.

Both IRUs and IPLCs can be either half-circuit or full-circuit. Full-circuit is one-stop shopping (OSS) with network peering and IP transit included. There's no need to liaison with other carriers for network-to-network interfacing (NNI); the carrier provides all circuit management and support. With a half-circuit connection, the customer is responsible for contracting with a carrier(s) for management and support at the far end.

Essentially, going half-circuit means managing two separate fiber circuits provided by two or more carriers. This arrangement, while often cheaper than full-circuit, adds the hassle of paying two (or more) separate invoices, currency conversion issues, transit fees, establishing point-of-contacts with representatives of all carriers terminating traffic, diligent traffic and bandwidth management, etc.

3. Can Your Business Afford Lightwave Networking Gear?

When a customer leases dark fiber, it receives dedicated strands, usually with availability and restoration supported by a service level agreement (SLA) that dark fiber providers will often customize. However, the customer must furnish all network gear at each point-of-presence (POP)—say, an Add-Drop Multiplexer (ADM)—and optical regenerators (to boost light intensity and eliminate signal attenuation) along the fiber route.

At the risk of understatement, the cost of acquiring this network equipment is not cheap. The personnel needed to configure, operate, maintain and monitor the gear and network also adds to the overall cost. If your business has the resources, staff, and expertise to run an extensive ISP or a multiservice network (MSN), then operating a dark fiber network is within your reach. Otherwise, businesses should consider whether or not they are prepared to troubleshoot and repair their own private networks. The carrier is responsible for only ensuring the integrity of the physical link itself.

We did a deep dive on WAN connectivity pricing, including dark fiber pricing factors, check it out here.

4. Scalability or Setup?

A turnkey lit fiber solution puts the onus of bandwidth availability and support on the provider, who offers SLAs to the customer. Yet, lit fiber bandwidth is fixed; while convenient and readily available, any scalability will take considerable time to deploy with lit fiber solutions.

With dark fiber, as we noted here, you "dictate the capabilities of the entire network’s architecture, speed, and security.” There are minimal limits to your bandwidth capabilities with dark fiber, with the gear you are connecting on both ends of the strand being the only control. For the most bandwidth-intensive enterprises, dark fiber is actually cost-competitive/cheaper than lit fiber and gives you complete control over how you scale your network.

With dark fiber, companies needing to increase bandwidth in a twinkling can do so within a predictable cost framework: often just a one-time Capex to purchase new optical equipment that supports higher throughput. Instead of paying more when using more data (the payment structure of most ISPs with lit fiber), a dark fiber network offers economies of scale with a fixed payment for unlimited data usage.

Another virtue of dark fiber is that the subscriber is entirely in charge of their destiny, meaning that you will not be subjected to move, add or change orders that require carrier intervention. This could very well be the reason Yoda said “If Once You Start Down The Dark Path, Forever Will It Dominate Your Destiny.” in Return of the Jedi

5. How Important Are Data Speeds, Latency, and Security?

With best effort services, most ISPs are rife with bottlenecks built into their network architecture at various points to monetize the carrier's services. That is not the case with dedicated WAN services, such as Dark Fiber.

Dark fiber networks ensure that your data travels the most direct path between point A and point B, quickening data speeds and lowering latency. Your IT team manages your dark fiber network, identifying performance issues and addressing them without waiting for ISP techs to intervene. When buying dark fiber, a good question for the provider is to ask how far the distance of the link is between both sites - the closer to a straight line, the lower the latency.

By its physical nature as a private network, dark fiber allows for the easy implementation of data security protocols. Since your data is segregated from the Internet, and even the carrier’s core network backbone, you're protected from outages that can arise from ISP’s.

Are You Ready for Dark Fiber?

If the overhead to run your networks continues to rise month after month due to ever-increasing data loads, it may be time to consider switching to dark fiber. The predictable costs, low latency, and complete control of your network are just a few of the benefits you can expect when you move over to the “dark side of fiber.”

Undoubtedly, taking the plunge into dark fiber should be carefully considered. Lightyear can help you select a proven and capable provider to plan, build, and launch a network customized to your needs, both now and for the future.

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