What Is a Fiber Optic Cable?

The Role of Fiber Optic Cables in Computer Networking and the Internet

Fiber Optics allow light and information to be transported over long distances.
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A fiber optic cable is a network cable that contains strands of glass fibers inside an insulated casing. They're designed for long distance, very high performance data networking and telecommunications.

Compared to wired cables, fiber optic cables provide higher bandwidth and can transmit data over longer distances.

Fiber optic cables support much of the world's internet, cable television and telephone systems.

How Fiber Optic Cables Work

Fiber optic cables carry communication signals using pulses of light generated by small lasers or light-emitting diodes (LEDs).

The cable consists of one or more strands of glass, each only slightly thicker than a human hair. The center of each strand is called the core, which provides the pathway for light to travel. The core is surrounded by a layer of glass called cladding that reflects light inward to avoid loss of signal and allow the light to pass through bends in the cable.

The two primary types of fiber cables are called single mode and multi mode fiber. Single mode fiber uses very thin glass strands and a laser to generate light while multi mode fibers use LEDs.

Single mode fiber networks often use Wave Division Multiplexing (WDM) techniques to increase the amount of data traffic that can be sent across the strand.  WDM allows light at multiple different wavelengths to be combined (multiplexed) and later separated (de-multiplexed), effectively transmitting multiple communication streams via a single light pulse.

Advantages of Fiber Optic Cables

Fiber cables offer several advantages over traditional long-distance copper cabling.

  • Fiber optics have a higher capacity. The amount of network bandwidth a fiber cable can carry easily exceeds that of a copper cable with similar thickness. Fiber cables rated at 10 Gbps, 40 Gbps and even 100 Gbps are standard.
  • Since light can travel much longer distances down a fiber cable without losing its strength, it lessens the need for signal boosters.
  • Fiber is less susceptible to interference. A traditional network cable requires special shielding to protect it from electromagnetic interference. While this shielding helps, it is not sufficient to prevent interference when many cables are strung together in close proximity to each other. The physical properties of glass and fiber cables avoid most of these issues.

Fiber to the Home (FTTH), Other Deployments, and Fiber Networks

Whereas most fiber is installed to support long distance connections between cities and countries, some residential internet providers have invested in extending their fiber installations to suburban neighborhoods for direct access by households. Providers and industry professionals call these "last mile" installations.

Some better known FTTH services in the market today include Verizon FIOS and Google Fiber. These services can provide gigabit (1 Gbps) internet speeds to each household. However, even though providers also offer lower cost, they typically also offer lower capacity packages to their customers.

  • FTTP (Fiber to the Premises): Fiber that's laid all the way up to the building.
  • FTTB (Fiber to the Building/Business/Block): The same as FTTP.
  • FTTC/N (Fiber to the Curb of Node): Fiber that's laid to the node but then copper wires complete the connection inside the building.
  • Direct fiber: Fiber that leaves the central office and is attached directly to one customer. This provides the greatest bandwidth but is more expensive.
  • Shared fiber: Similar to direct fiber except that as the fiber gets close to the premises of nearby customers, it's split into others fibers for those users.

What Is Dark Fiber?

The term dark fiber (often spelled dark fibre or called unlit fibre) most commonly refers to installed fiber optic cabling that is not currently being used.

It sometimes also refers to privately operated fiber installations.