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.
Fiber is preferred over electrical cabling when high bandwidth, long distance, or immunity to electromagnetic interference are required.
Optical fibres are made up of three components:
• Core – Thin glass centre of the fibre where the light travels
• Cladding – Outer optical material surrounding the core that reflects the light back into the core.
• Buffer coating – Plastic coating that protects the fibre from damage and moisture.
The use and demand for optical fiber has grown tremendously and optical-fiber applications are numerous. Telecommunication applications are widespread, ranging from global networks to desktop computers. These involve the transmission of voice, data, or video over distances of less than a meter to hundreds of kilometers, using one of a few standard fiber designs in one of several cable designs.
Carriers use optical fiber to carry plain old telephone service (POTS) across their nationwide networks. Local exchange carriers (LECs) use fiber to carry this same service between central office switches at local levels, and sometimes as far as the neighborhood or individual home (fiber to the home [FTTH]).
Optical fiber is also used extensively for transmission of data. Multinational firms need secure, reliable systems to transfer data and financial information between buildings to the desktop terminals or computers and to transfer data around the world. Cable television companies also use fiber for delivery of digital video and data services. The high bandwidth provided by fiber makes it the perfect choice for transmitting broadband signals, such as high-definition television (HDTV) telecasts.
Intelligent transportation systems, such as smart highways with intelligent traffic lights, automated tollbooths, and changeable message signs, also use fiber-optic-based telemetry systems.
Another important application for optical fiber is the biomedical industry. Fiber-optic systems are used in most modern telemedicine devices for transmission of digital diagnostic images. Other applications for optical fiber include space, military, automotive, and the industrial sector.
The disadvantages of optical fibres are:
• Price – Even though the raw material for making optical fibres, sand, is abundant and cheap, optical fibres are still more expensive per metre than copper. Although, one fibre can carry many more signals than a single copper cable and the large transmission distances mean that fewer expensive repeaters are required.
• Fragility – Optical fibres are more fragile than electrical wires.
• Affected by chemicals – The glass can be affected by various chemicals including hydrogen gas (a problem in underwater cables.)
• Opaqueness – Despite extensive military use it is known that most fibres become opaque when exposed to radiation.
• Requires special skills – Optical fibres cannot be joined together as a easily as copper cable and requires additional training of personnel and expensive precision splicing and measurement equipment.