Fiber Optic Cables

Optical fiber

Optical fiber is the technology associated with data transmission using light pulses travelling along with a long fiber which is usually made of plastic or glass. Metal wires are preferred for transmission in optical fiber communication as signals travel with fewer damages.
An optical fiber (or fibre in British English) is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data transfer rates) than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer. Fibers are also used for illumination and imaging, and are often wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. Specially designed fibers are also used for a variety of other applications, some of them being fiber optic sensors and fiber lasers.

Fiber optics is also commonly used in telecommunication services such as internet, television and telephones. For example, Verizon and Google use fiber optics in their Verizon FIOS and Google Fiber services, respectively, providing gigabit internet speeds to users.
Fiber optic cables are used as they hold a number of advantages over copper cables, such as higher bandwidth and transmit speeds.
A fiber optic cable can contain a varying number of these glass fibers - from a few up to a couple hundred. Surrounding the glass fiber core is another glass layer called cladding. A layer known as a buffer tube protects the cladding, and a jacket layer acts as the final protective layer for the individual strand.

The technique of transmitting data from one location to another by transmitting infrared light pulses using optical fiber is known as fiber optic communication. Here, the light is in the form of a carrier signal that is changed to hold the data. The fiber optic cables replace the electrical cables whenever long distance, high bandwidth, and resistance to electromagnetic interference are necessary.
Fiber-optic communication is mainly used for transmitting voice, video & telemetry using LANs. In many telecommunication companies, optical fiber is used for transmitting the signals of telephone, cable TV signals, Internet communication. In Bell Labs, the researchers have investigated and reached a record of BW distance 100 petabit × kilometers for each second with fiber-optic communication.

How fiber optics works
Fiber optics transmit data in the form of light particles -- or photons -- that pulse through a fiber optic cable. The glass fiber core and the cladding each have a different refractive index that bends incoming light at a certain angle. When light signals are sent through the fiber optic cable, they reflect off the core and cladding in a series of zig-zag bounces, adhering to a process called total internal reflection. The light signals do not travel at the speed of light because of the denser glass layers, instead traveling about 30% slower than the speed of light. To renew, or boost, the signal throughout its journey, fiber optics transmission sometimes requires repeaters at distant intervals to regenerate the optical signal by converting it to an electrical signal, processing that electrical signal and retransmitting the optical signal.
Fiber optic cables are moving toward supporting up to 10-Gbps signals. Typically, as the bandwidth capacity of a fiber optic cable increases, the more expensive it becomes.
Light travels down a fiber optic cable by bouncing off the walls of the cable repeatedly. Each light particle (photon) bounces down the pipe with continued internal mirror-like reflection.
The light beam travels down the core of the cable. The core is the middle of the cable and the glass structure. The cladding is another layer of glass wrapped around the core. Cladding is there to keep the light signals inside the core.

Types of Optical Fibers
Single-Mode Fibers: Single-mode fibers are used to transmit one signal per fiber; these fibers are used in telephone and television sets. Single-mode fibers have small cores.
Single mode fiber is the simplest structure. It contains a very thin core, and all signals travel straight down the middle without bouncing off the edges. Single mode fiber optic cables are typically used for CATV, Internet, and telephone applications, where the signals are carried by single mode fibers wrapped into a bundle.
Multi-Mode Fibers: Multimode fibers are used to transmit many signals per fiber; these signals are used in computer and local area networks that have larger cores. Multimode fiber is the other type of fiber optic cable. It is about 10 times larger than a single mode cable. The light beams can travel though the core by following a variety of different paths, or in multiple different modes. These cable types can only send data over short distances. Therefore, they are used, among other applications, for interconnecting computer networks.
There are four types of multimode fiber optic cables, identified by “OM” (optical multimode). An industry association designated them as OM1, OM2, OM3 and OM4. They are described by ISO/IEC 11801. OM4’s standard was approved by TIA/EIA 492AAAD. Each OM has a minimum Modal Bandwidth requirement.

Uses of Optical Fiber
You may have seen plastic fibers carrying colored lights in decorative applications. What you may not have seen are the real glass fiber optic cables that are now the foundation of our communication and computer networks. Many thousands of miles of installed fiber optic cable carry many types of information underground, in tunnels, building walls, ceilings, and other places you don’t see. For examples of uses of optical fiber in our daily life include applications such as:

• computer networking
• broadcasting
• medical scanning
• military equipment

In recent years, other fiber optic uses have arisen. Fiber optic cables have become the backbone for MANs, WANs and LANs. There has been a trend toward “FTTX” or “Fiber to the XXXX” applications. That is, for example, Fiber to the:

• Home (FTTH)
• Curb (FTTC)
• Premise (FTTP)
• Building (FTTB)
• Node (FTTN)

Initially, fiber optic uses were primarily trunk cable lines designed to carry signals to larger populated areas. Over time, theses cables have extended their reach to the home, the building, etc., giving rise to the FTTX trend.

Some of the most popular uses of fibre optic cables are :

• Internet. Fibre optic cables transmit large amounts of data at very high speeds.
• Computer Networking.
• Surgery and Dentistry.
• Automotive Industry.
• Telephone.
• Lighting and Decorations.
• Mechanical Inspections.
• Cable Television.

Source: Few websites, Wikipedia...