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A System view of Optical Fiber Communication

A System view of Optical Fiber Communication. Prepared by. Ismail Ali Al-Qaram. Zeyad Al-Qabbani. Ali Kamel Al-Awami. Overview:. An optical fiber is a glass or plastic fiber designed to guide light along its length by total internal reflection.

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A System view of Optical Fiber Communication

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  1. A System view of Optical Fiber Communication

  2. Prepared by Ismail Ali Al-Qaram Zeyad Al-Qabbani Ali Kamel Al-Awami

  3. Overview: An optical fiber is a glass or plastic fiber designed to guide light along its length by total internal reflection Optical fibers are widely used in fiber-optic communication, which permits digital data transmission over longer distances and at higher data rates than electronic communication.

  4. History Optical fiber was developed in 1970 by Corning Glass Works with attenuation low enough for communication purposes (about 20dB/km) • 1st generation operated at a wavelength 0.8 µm • 2nd generation 1.3µm • 3rd generation 1.55µm • 4th generation 1.6µm • 5th generation extending the wavelength range over which a WDM system can operate.

  5. Types of optical fiber: • SINGLE-MODE FIBER • - narrow core, diameter (8 microns or less). • - Light travels parallel to the axis. • - little pulse dispersion. • Uses: • Telephone & cable television networks

  6. STEP-INDEX MULTIMODE FIBER - large core, diameter: 100 microns - travel in direct route, other rays zigzag as they bounce off the cladding - pulse, spread out, losing its well-defined shape • Uses: • short distances, for example an endoscope

  7. GRADED-INDEX MULTIMODE FIBER - core has refractive index that diminishes gradually from the center axis out toward the cladding. - the light rays move down the axis advance more slowly than those near the cladding. - light in the core curves helically. - shortened path & higher speed less dispersion.

  8. Comparison

  9. BASIC CABLE DESIGN • Two basic cable designs: • 1- Loose-Tube Cable: • Uses: • - used in outside-plan installations. • Properties: - holds up to 12 fibers per buffer tube. - fibers are loosely packaged in gel filled buffer tubes to repel water. - endure outside temperatures and high moisture. - Typically, distance not to exceed 50 feet.

  10. 2-Tight-Buffered Cable • Uses: - often used for intra-building • Properties: • no gel, connectors terminated directly onto the fiber without difficult to use breakout kits • less expensive installation - (Temperature rating -40ºC to +85ºC). - Typically, long distance

  11. Communication Applications • Fiber-optic cable is used by many telecommunications companies to transmit telephone signals, internet communication, and cable television signals, sometimes all on the same optical fiber

  12. Communication System Using Optical Fiber • Components of the Transmission System: • Transmitters • Amplifiers • Receivers

  13. Transmitters: - The most commonly used optical transmitters are semiconductor devices such as Light emitting diodes (LEDs) and laser diodes. - A semiconductor laser emits light through stimulated emission rather than spontaneous emission high output power (~100 mW) - efficiency (~50%) LEDs: - wide spectral width of 30-60 nm - Output power 100 microwatts - efficiency (~1%) laser diodes: - wide spectral width of0.81-0.87 µm - High data rates, long distances

  14. Amplifiers: - Solution for fiber attenuation and fiber distortion. - amplifies the optical signal directly without having to convert the signal into the electrical domain. - Made by doping a length of fiber with an rare-earth mineral (erbium), and pumping it with light from a laser with a shorter wavelength than the communications signal (typically 980 nm) • Recivers: - The main component of an optical receiver is a photo detector that converts light into electricity through the photoelectric effect. - detectors are also used due to their suitability for circuit integration in regenerators and wavelength-division multiplexers

  15. Wavelength-Division Multiplexing (WDM) : • WDM is dividing the wavelength capacity of an optical fiber into multiple channels. • Requirements: • - multiplixer in the transmition. • - demultiplexer in the receiving. • bandwidth can be divided up to 80 channels • - carry information at around 14 Terabits/s over 160 km of fiber.

  16. Attenuation • - attenuation is caused by a combination of material absorption, and connection losses. • attenuation in modern fiber is • about 1000 db/km. • - other causes of attenuation are physical stresses to the fiber, microscopic fluctuations in density, and imperfect splicing techniques.

  17. Comparison between electrical transmission and fiber optics

  18. THE END Thanks for listening

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