Dark Fiber is private, nonpublic routable network in underground conduit or arial runs typically to connect point to point locations.  Lit Fiber can be defined similarly however it’s often used to denote a “carrier” is on-net with their infrastructure.  This on-net services typically provide global WAN options such as Internet, Private Line, MPLS or other SDWAN capable services.


Lit Fiber options do provide cheaper alternatives when you look to connect to some of the best diverse ISPs.   


Pros and Cons of Dark Fiber


  1. Private & non-routable over the internet but can support private LAN/WAN
  2. You or the carrier control the capacity used and allocated for the locations you want to route traffic to.
  3. Often, dark fiber is diverse from other carriers for some or all components.  Diversity could exist in separate conduits however even if it’s in the same collapsed underground facility, there is equipment diversity between your org and another.



  1. Maintenance both on the fiber & equipment, someone must maintain card failures, training & support of the infrastructure.
  2. Fiber Cuts – no matter what route you build, the chances of someone not calling the local utilities to map out underground utilities such as fiber, then place a backhoe through causing a cut it very common.

Cost – Dark Fiber typically costs more, often double compared to a share private line with other customers on a carrier circuit.   Additionally, the cost of fiber over a 36-month period (typical contract term if you outsource the lease) lowers approximately 30-40%.  Keep this in mind and work with your FinOps team if this supports cloud to determine an Opex vs Capex mode.  It is recommended to look at the Telecom Expense across the dark fiber plant an organization has to be sure of cost management.


We provide free Fiber route mapping between client locations including DataCenters to Cloud onramps

Pictured below is Equinix’s DC6 facility in Datacenter alley in Ashburn, VA.  Attempting to identify fiber connectivity on your own can be daunting and risky if you do not fully understand the complexities.


Using Lit Dark Fiber to support your Cloud Connectivity and Cloud Onramps

Many organizations who take a methodically approach to Software Defined Cloud Interconnect (SDCI) options, use Lit Fiber as part of their design.  Watch this webinar where we cover SDCI options and best practices.



KMZ File for Dark Fiber or other Lit Fiber Solutions

Most carriers use Google .KMZ File formats to map out their physical dark fiber and lit routes in a geography.   Often a carrier will provide access to these proprietary files if a NDA is signed.  Many of the traditional Local Exchange Carriers will not provide KMZ files easily because it’s proprietary and can be viewed as a competitive and security concern to simply show where lit fiber resides.

Macronet Services does have tools to help define a solid dark fiber network, 20+ years of experience and a maniacal focus on engineered solutions.  Please contact us for a quick assessment.