Home | Articles | About | Contact | Forum |
Friday, September 20, 2019

Lunarpages.com Web Hosting

Mailing List

By Joining the mailing list you will be notified of site updates.

Show Your Support For
This Site By Donating:

Audience: System Admins - I.T. Managers
Last Updated: 6/6/2011 1:50:09 PM
**All times are EST**

Dark Fiber Definition and Uses

By Erik Rodriguez

Tags: Dark Fiber, Leased Dark Fiber, CWDM, DWDM with Fiber, Dark Fiber vs. Leased Line, Metro Ethernet

This article provides information on what dark fiber is, and how it is used. Dark fiber is used almost exclusively by telecom providers and data centers. It has several popular uses and they are explained in detail below.

What is dark fiber?

Dark fiber is just what it sounds like, fiber that is not "lit" therefore it is not being used. Fiber optic cable is very expensive to bury. It requires a ton of permitting, construction plans, and labor. Due to the various hoops that need to be jumped, fiber is often buried in bulk. Meaning, if they are going to run fiber down a main street or highway, they run a lot.

Uses for dark fiber

Dark fiber can be used for many different things. Voice, data, or a combination of the two can all take advantage of dark fiber. Some organizations such as government or educational institutions may lease dark fiber from the owner. The owner is usually a city or telecom provider. Leasing such fiber is not cheap and some providers refuse to lease dark fiber to the public.


Dark fiber is usually provided as a single or group of fiber optic cables. Organizations using dark fiber are generally responsible for providing equipment on both ends. This equipment usually comes in the form of multiplexing equipment specific to the application. Short distance dark fiber can use CWDM. Long distances will generally use DWDM. The multiplexing gear allows organizations to send multiple streams of voice and/or data over a single fiber. There are many different types of multiplexers that can accept multiple fiber optic cables.

Dark fiber vs. leased line

Dark fiber differs from other leased line technologies such as a DS-3 or OC-3 because it provides a bare medium. The bare medium means a "blank" strand of fiber and not a completed transport solution from a telecom/service provider. For example, a DS-3 is a TDM (time division multiplexed) solution in which the service provider performs the multiplexing inside their own network. The customer is handed a usable circuit be it point-to-point or Internet transport. Using a DS-3, you are stuck at ~45 Mbps, and cannot add your own multiplexing equipment as the circuit is already multiplexed.

Real world use

Service providers that have multiple data centers often use dark fiber and attach multiplexers to each end so they can transport data from different locations. For example, and service provider may have a data center in New Jersey, and Montreal. The distance between these data centers is fairly large, so they will often use a dark fiber or fibers running CWDM. This would allow them to transfer data at multiple Gbps.

Their alternative would be to lease point-to-point connections such as DS-3s or more realistically 10 Gbps Metro Ethernet circuits. The cost of leasing a point-to-point Metro Ethernet connection at 1 Gbps would not make sense if they could utilize dark fiber running CWDM or DWDM to move voice and data. Often, data center will use this dark fiber links between data centers to backhaul transport to the Internet from other data centers in the event of a failure or capacity issue. Transporting data across a dark fiber is shown below:

Contact Us

If you found this information useful, click the +1 button

Your E-mail:


Type verification image:
verification image, type it in the box


NOTE: this form DOES NOT e-mail this article, it sends feedback to the author.

Juniper SRX anti-spam filtering config
Windows Server 2008 Clustering Configuration
Windows 2008 R2 Network Load Balancing (NLB)
Extreme Networks: Downloading new software image
Juniper SRX save config to USB drive
Juniper SRX logout sessions
Extreme Networks Syslog Configuration
Command line drive mapping
Neoscale vs. Decru
Data Security vs. Data Protection
Juniper SRX Cluster Configuration
HOWTO - Create VLAN on Extreme Switch
Using a Non-local Colocation Facility
Linux Server Administration
IT Chop Shops
Flow Viewers: SFLOW, NetFLOW, and JFLOW
Exchange 2007 Back Pressure
IPtables open port for specific IP
Politics in IT Departments
HOWTO - Block Dropbox
Cisco IOS Cheat Sheet
Subnet Cheat Sheet
Design a DMZ Network
How DNS works
Firewall Configuration
Juniper SSG Firewalls
Server Management
Configuring VLANs
Runlevels in Linux
Server Clustering
SONET Networks
The Red Hat Network
Server Colocation
Complicated Linux Servers
Dark Fiber
Data Center Network Design
Firewall Types
Colocation Bandwidth

Copyright © 2002-2016 Skullbox.Net All Rights Reserved.
A division of Orlando Tech Works, LLC
By using this site you agree to its Terms and Conditions.
Contact Erik Rodriguez