Dark fiber
Encyclopedia
A dark fiber or unlit fiber is an unused Optical fiber
, available for use in fiber-optic communication
.
The term dark fiber was originally used when referring to the potential network capacity of telecommunication infrastructure, but now also refers to the increasingly common practice of leasing fiber optic cables from a network service provider
.
work required. This includes planning and routing, obtaining permissions, creating ducts and channels for the cables, and finally installation and connection. This work usually accounts for more than 60% of the cost of developing fiber networks. For example, in Amsterdam's city-wide installation of a fiber network, roughly 80% of the costs involved were labor, with only 10% being fibre. It therefore makes sense to plan for, and install, significantly more fiber than is needed for current demand, to provide for future expansion and provide for network redundancy
in case any of the cables fail.
Many fiber optic cable owners such as railroads or power utilities have always added additional fibers for lease to other carriers.
In common vernacular, dark fiber may sometimes still be called "dark" if it has been lit by a fiber lessee and not the cable's owner.
, a large number of telephone companies
built optical fiber networks, each with the business plan of cornering the market
in telecommunications by providing a network with sufficient capacity to take all existing and forecast traffic for the entire region served. This was based on the assumption that telecoms traffic, particularly data traffic, would continue to grow exponentially
for the foreseeable future.
The availability of wavelength-division multiplexing
further reduced the demand for fiber by increasing the capacity that could be placed on a single fiber by a factor of as much as 100. As a result, the wholesale price of data traffic collapsed. A number of these companies filed for bankruptcy
protection as a result. Global Crossing and Worldcom are two high profile examples.
Just as with the Railway Mania
, the misfortune of one market sector
became the good fortune of another, and this overcapacity created a new telecommunications market sector.
s would not sell dark fiber to end users, because they believed selling access to this core asset would cannibalize their other, more lucrative services. Incumbent carriers in the US were required to sell dark fiber to competitive local exchange carrier
s as Unbundled Network Element
s (UNE), but they have successfully lobbied to reduce these provisions for existing fiber, and eliminated it completely for new fiber placed for fibre to the premises (FTTP) deployments.
Competitive local carriers were not required to sell dark fiber, and many do not, although fiber swaps between competitive carriers are quite common. This increases the reach of their networks in places where their competitor has a presence, in exchange for provision of fiber capacity on places where that competitor has no presence. This is a practice known in the industry as "coopetition
".
Meanwhile, other companies arose specializing as dark fiber providers. Dark fiber became more available when there was enormous overcapacity after the boom years of the late 1990s through 2001. The market for dark fiber tightened up with the return of capital investment to light up existing fiber, and with mergers and acquisitions resulting in consolidation of dark fiber providers.
Dark fiber capacity is typically used by network operators to build SONET
and dense wavelength division multiplexing (DWDM) networks, usually involving meshes of self-healing ring
s. Now, it is also used by end-user enterprises to expand Ethernet
local area networks, especially since the adoption of IEEE standards for Gigabit Ethernet
and 10 Gigabit Ethernet
over single-mode optical fiber
. Running Ethernet networks between geographically separated buildings is a practice known as "WAN
elimination".
, Moore's law
holds true with fiber optics. The amount of data coming out of an optical fiber is doubling every nine months. Thus, excluding the transmission equipment upgrades, the cost of transmitting a bit over an optical network decreases by half every nine months. The availability of dense wavelength-division multiplexing DWDM and coarse wavelength division multiplexing CWDM is rapidly bringing down the cost of networking, and further progress seems assured.
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
, available for use in fiber-optic communication
Fiber-optic communication
Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information...
.
The term dark fiber was originally used when referring to the potential network capacity of telecommunication infrastructure, but now also refers to the increasingly common practice of leasing fiber optic cables from a network service provider
Network service provider
A network service provider is a business or organization that sells bandwidth or network access by providing direct backbone access to the Internet and usually access to its network access points...
.
For capacity expansion
One reason that dark fiber exists in well-planned networks is that much of the cost of installing cables is in the civil engineeringCivil engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...
work required. This includes planning and routing, obtaining permissions, creating ducts and channels for the cables, and finally installation and connection. This work usually accounts for more than 60% of the cost of developing fiber networks. For example, in Amsterdam's city-wide installation of a fiber network, roughly 80% of the costs involved were labor, with only 10% being fibre. It therefore makes sense to plan for, and install, significantly more fiber than is needed for current demand, to provide for future expansion and provide for network redundancy
Redundancy (engineering)
In engineering, redundancy is the duplication of critical components or functions of a system with the intention of increasing reliability of the system, usually in the case of a backup or fail-safe....
in case any of the cables fail.
Many fiber optic cable owners such as railroads or power utilities have always added additional fibers for lease to other carriers.
In common vernacular, dark fiber may sometimes still be called "dark" if it has been lit by a fiber lessee and not the cable's owner.
Overcapacity
In the dot-com bubbleDot-com bubble
The dot-com bubble was a speculative bubble covering roughly 1995–2000 during which stock markets in industrialized nations saw their equity value rise rapidly from growth in the more...
, a large number of telephone companies
Telephone company
A telephone company is a service provider of telecommunications services such as telephony and data communications access. Many were at one time nationalized or state-regulated monopolies...
built optical fiber networks, each with the business plan of cornering the market
Cornering the market
In finance, to corner the market is to get sufficient control of a particular stock, commodity, or other asset to allow the price to be manipulated. Another definition: "To have the greatest market share in a particular industry without having a monopoly...
in telecommunications by providing a network with sufficient capacity to take all existing and forecast traffic for the entire region served. This was based on the assumption that telecoms traffic, particularly data traffic, would continue to grow exponentially
Exponential growth
Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...
for the foreseeable future.
The availability of wavelength-division multiplexing
Wavelength-division multiplexing
In fiber-optic communications, wavelength-division multiplexing is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths of laser light...
further reduced the demand for fiber by increasing the capacity that could be placed on a single fiber by a factor of as much as 100. As a result, the wholesale price of data traffic collapsed. A number of these companies filed for bankruptcy
Bankruptcy
Bankruptcy is a legal status of an insolvent person or an organisation, that is, one that cannot repay the debts owed to creditors. In most jurisdictions bankruptcy is imposed by a court order, often initiated by the debtor....
protection as a result. Global Crossing and Worldcom are two high profile examples.
Just as with the Railway Mania
Railway Mania
The Railway Mania was an instance of speculative frenzy in Britain in the 1840s. It followed a common pattern: as the price of railway shares increased, more and more money was poured in by speculators, until the inevitable collapse...
, the misfortune of one market sector
Market sector
The term market sector is used in economics and finance to describe a set of businesses that are buying and selling such similar goods and services that they are in direct competition with each other...
became the good fortune of another, and this overcapacity created a new telecommunications market sector.
Market
For many years incumbent local exchange carrierIncumbent local exchange carrier
An ILEC, short for incumbent local exchange carrier, is a local telephone company in the United States that was in existence at the time of the breakup of AT&T into the Regional Bell Operating Companies , also known as the "Baby Bells." The ILEC is the former Bell System or Independent Telephone...
s would not sell dark fiber to end users, because they believed selling access to this core asset would cannibalize their other, more lucrative services. Incumbent carriers in the US were required to sell dark fiber to competitive local exchange carrier
Competitive local exchange carrier
A competitive local exchange carrier , in the United States, is a telecommunications provider company competing with other, already established carriers ....
s as Unbundled Network Element
Unbundled Network Element
Unbundled Network Elements are a requirement mandated by the United States Telecommunications Act of 1996. They are the parts of the telecommunications network that the incumbent local exchange carriers are required to offer on an unbundled basis...
s (UNE), but they have successfully lobbied to reduce these provisions for existing fiber, and eliminated it completely for new fiber placed for fibre to the premises (FTTP) deployments.
Competitive local carriers were not required to sell dark fiber, and many do not, although fiber swaps between competitive carriers are quite common. This increases the reach of their networks in places where their competitor has a presence, in exchange for provision of fiber capacity on places where that competitor has no presence. This is a practice known in the industry as "coopetition
Coopetition
Coopetition or Co-opetition is a neologism coined to describe cooperative competition....
".
Meanwhile, other companies arose specializing as dark fiber providers. Dark fiber became more available when there was enormous overcapacity after the boom years of the late 1990s through 2001. The market for dark fiber tightened up with the return of capital investment to light up existing fiber, and with mergers and acquisitions resulting in consolidation of dark fiber providers.
Dark fiber capacity is typically used by network operators to build SONET
Sonet
Sonet may refer to:* Sonet Records, European record label* Synchronous optical networking * Saab Sonett...
and dense wavelength division multiplexing (DWDM) networks, usually involving meshes of self-healing ring
Self-healing ring
A self-healing ring, or SHR, is a telecommunications term for loop network topology, a common configuration in telecommunications transmission systems. Like roadway and water distribution systems, a loop or ring is used to provide redundancy...
s. Now, it is also used by end-user enterprises to expand Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
local area networks, especially since the adoption of IEEE standards for Gigabit Ethernet
Gigabit Ethernet
Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second , as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks where it performed...
and 10 Gigabit Ethernet
10 Gigabit Ethernet
The 10 gigabit Ethernet computer networking standard was first published in 2002. It defines a version of Ethernet with a nominal data rate of 10 Gbit/s , ten times faster than gigabit Ethernet.10 gigabit Ethernet defines only full duplex point to point links which are generally connected by...
over single-mode optical fiber
Single-mode optical fiber
In fiber-optic communication, a single-mode optical fiber is an optical fiber designed to carry only a single ray of light . Modes are the possible solutions of the Helmholtz equation for waves, which is obtained by combining Maxwell's equations and the boundary conditions...
. Running Ethernet networks between geographically separated buildings is a practice known as "WAN
Wide area network
A wide area network is a telecommunication network that covers a broad area . Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations...
elimination".
Emerging Markets
In the last decade, many higher education institutions have bought up large quantities of existing fiber optics sitting dormant. Starting in 1999, Larry Starr, a technology director from the University of Illinois, connected the Urbana-Champaign campus to major academic, research, and telecommunications facilities in the Chicago area . At the same time, other schools began creating large urban networks to directly connect their school campuses with hospitals and large telecommunications companies in metropolitan areas. Since then, the U.S. research and education (R&E) community have been aggressively pursuing a revolutionary new means for delivering advanced networking capabilities. With the plummeting prices of fiber due to the over abundance, the option to own fiber networks has stomped out the competition leasing of commercial circuits elsewhere. Experts say that a mile of dark fiber that in the past would sell for $1,200 has sold, for as low $200 or less. The downturn in telecommunications has offered significant savings to schools, since intercity networks may include several hundred to several thousand miles of fiber optic cable.Variations
- Managed dark fiber is a form of wavelength-division multiplexed access to otherwise dark fiber where a simple "pilot" signal is beamed into the fiber by the fiber provider for management purposes using a transponder tuned to the assigned wavelength. DWDM systems generally require central management because their closely spaced wavelengths are subject to disruption by signals on adjacent wavelengths that are not within tightly controlled parameters, especially if amplification is required for signal transmission over 100 km.
- Virtual dark fiber using wavelength multiplexing allows a service provider to offer individual wavelengths ("lambdaLambdaLambda is the 11th letter of the Greek alphabet. In the system of Greek numerals lambda has a value of 30. Lambda is related to the Phoenician letter Lamed . Letters in other alphabets that stemmed from lambda include the Roman L and the Cyrillic letter El...
s" (λ) or "colors"), where access to a dark narrowbandNarrowbandIn radio, narrowband describes a channel in which the bandwidth of the message does not significantly exceed the channel's coherence bandwidth. It is a common misconception that narrowband refers to a channel which occupies only a "small" amount of space on the radio spectrum.The opposite of...
wavelength-division multiplexing (WDMWavelength-division multiplexingIn fiber-optic communications, wavelength-division multiplexing is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths of laser light...
) optical channel is provided over a wavelength division multiplexed fiber network that is managed at the physical level, but unlit by the network provider. This is typically done using coarse wavelength division multiplexing CWDM because the wider 20 nm spacing of the wave bands makes these systems much less susceptible to interference.
Rate of expansion
According to Gerry Butters, the former head of Lucent's Optical Networking Group at Bell LabsBell Labs
Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...
, Moore's law
Moore's Law
Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....
holds true with fiber optics. The amount of data coming out of an optical fiber is doubling every nine months. Thus, excluding the transmission equipment upgrades, the cost of transmitting a bit over an optical network decreases by half every nine months. The availability of dense wavelength-division multiplexing DWDM and coarse wavelength division multiplexing CWDM is rapidly bringing down the cost of networking, and further progress seems assured.