How Optical Fiber Communication Works

Optical Fiber communication is a method of transmitting information from one place to another, signal are sent in the form of light which is first converted into the light from electrical signals and transmitted and converted back to electrical signal on the recieving side. It suitable for transmitting of video,voice and telemetry through local area networks, computer networks, or across long distances.

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 fiber is used by many telecommunications companies to transmit telephone signals, Internet communication, and cable television signals.


Transmitter

Semiconductor devices such as light-emitting diodes (LEDs) and laser diodes are the most commonly used optical transmitters. The difference between LEDs and laser diodes is that LEDs produce incoherent light, while laser diodes produce coherent light. For use in optical communications, semiconductor optical transmitters must be designed to be compact, efficient and reliable, while operating in an optimal wavelength range and directly modulated at high frequencies.


Receiver

An optical receiver is a photodetector which converts light into electricity using the photoelectric effect. The primary photodetectors for telecommunications are made from Indium gallium arsenide. The photodetector is typically a semiconductor-based photodiode. Several types of photodiodes include p-n photodiodes, p-i-n photodiodes, and avalanche photodiodes. Metal-semiconductor-metal (MSM) photodetectors are also used due to their suitability for circuit integration in regenerators and wavelength-division multiplexers.

Wavelength-division multiplexing

Wavelength-division multiplexing (WDM) is the technique of transmitting multiple channels of information through a single optical fiber by sending multiple light beams of different wavelengths through the fiber, each modulated with a separate information channel. This allows the available capacity of optical fibers to be multiplied. This requires a wavelength division multiplexer in the transmitting equipment and a demultiplexer (essentially a spectrometer) in the receiving equipment. Arrayed wave-guide gratings are commonly used for multiplexing and demultiplexing in WDM. Using WDM technology now commercially available, the bandwidth of a fiber can be divided into as many as 160 channels to support a combined bit rate in the range of 1.6 Tbit/s.

Characteristics of Fiber Optic Communication

The following characteristics listed below are important to be discussed and makes it a good mode of communication.

  1. Smaller diameter : The diameter of Optical fiber cable is about 300 micrometers in diameter making it to be smaller than the thickness of a human hair.
  2. Light-weight : The Optical fiber cable is light in weight compared to the copper cable.
  3. Bandwidth : Single laser light dispersion means that a good amount of signal can be transmitted (Information being transferred in bits) per second which results in high bandwidth for long distances.
  4. Long-distance signal transmission : Laser light doesn’t disperse, it can be easily transmitted over long distances.
  5. Transmission security : Using Optical fiber makes the data more secured because of encryption and no presence of the electromagnetic.
  6. Low attenuation : The fiber is made of glass and laser is traveling through it, the signal transmitted has only 0.2 dB/km loss.

Applications of Optical Fiber

In the Telecommunication industry optical fiber communication are mostly used for:

  • Cable Television Signal transmission.
  • Telephone Signals transmission.
  • Internet Communication.
  • Optical fibers are also used in homes, industries, offices for long distance as well as for small distance communication.

Advantages of Optical Fiber Communication

  1. No Interference: Fiber-optic cables are immune to problems that arise with electrical cables, such as ground loops or electromagnetic interference (EMI) including nuclear electromagnetic pulses.
  2. Resistance to corrosion due to non-metallic transmission medium.
  3. High electrical resistance: Making it safe to use near high-voltage equipment or between areas with different earth potentials.
  4. Lighter weight: Compared with electrical cables, fiber-optic cables are very lightweight. Example it is used in aircraft.
  5. No sparks: Important in flammable or explosive gas environments.
  6. Easy Amplification: A large number of channels can be re-amplified in a single fiber amplifier if required for very large transmission distances.
  7. Large Transmission capacity: With a single silica fiber it can carry over hundreds of thousands of telephone channels, utilizing only a small part of the theoretical capacity.
  8. Not electromagnetically radiating, and difficult to tap without disrupting the signal—important in high-security environments.
  9. Much smaller cable size: Important where pathway is limited, such as networking an existing building, where smaller channels can be drilled and space can be saved in existing cable ducts and trays.
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