Fibre Optic Cable

Fibre Optic Cable

(Communication Terms – Applications – Advantages & Disadvantages)

 

Definition

A fibre optic cable is a network cable that contains a glass core and cladding, buffer coating, strength members and an outer jacket. In fibre optic cables light pulses are used for sending information. These cables were designed for long distance and very high bandwidth communications.

 

Types of Fibre Optic Cable

  • Single-Mode: transmit infrared laser light and have small cores (about 9 microns in diameter).
  • Multi-Mode: transmit infrared light from LEDs and have larger cores (62.5 microns in diameter).

 

Fibre Optic Communication Terms

  • Absorption: A cause of attenuation where light signal is absorbed into the glass during transmission.
  • Attenuation: Optical loss of power. Attenuation is expressed in dB loss per length of cable. Attenuation is caused by absorption and scattering.
  • Attenuator: It’s a device used for reducing the power of an optical signal.
  • Back Reflection: A measure of the light reflected off the polished end of a fibre connector. Expressed in negative dB relative to incident power.
  • Bandwidth: The range of signal frequencies that a fibre optic cable will transmit.
  • Buffer: Protective coating over the fibre.
  • Insertion Loss: Attenuation caused by the insertion of a device (such as a connection point) to a cable.
  • Loss Budget: Maximum amount of power that is allowed to be lost per optical link.
  • Multimode: Type of fibre optic cable where the core diameter is much larger than the wavelength of light being transmitted. Two common multimode fibre optic cable types are 50/125 and 62.5/125.
  • Return Loss: The ratio of the power into a cable and the power of the light returning back to the fibre. This measurement can be expressed in positive decibel units (dB). A higher number is preferred. Return Loss = 10 log (incident power / returning back power).
  • Scattering: A cause of attenuation optic signal. Scattering occurs when light collides with individual atoms in the glass of cable.
  • Single mode: A type of fibre optic cable with a small core that allows only one mode of light to propagate.
  • Wavelength: A means of measuring light color. Expressed in nanometers (nm).

 

Uses of Optic Fiber Cable

  • Medical: Fibre optic cables are being used as lasers for surgeries, light guides and imaging tools.
  • Data Transmission: These cables are now highly being installed for data transmission over networks.
  • Networking: These cables are used for connecting servers and users in a network and increase accuracy and speed of data transmission in a network.
  • Broadcast: Broadcast/cable companies use fibre optic cables for wiring HDTV, CATV, video on-demand, internet and other applications.

 

Advantages of Fibre Optic Cable

  • Less Expensive: For long distance transmissions, fibre optic cable is much less expensive than pure copper network cable.
  • Inflammable: As no electricity passes through fibre optic cable, no fire hazard exists.
  • Lightweight: Fibre optic cable is much less in weight than the copper cable and it takes less space in the ground.
  • Digital Signals: Fibre optics are very suitable for transmitting digital information, that’s why fibre optic cables are preferred in computing networks.
  • Light Signals: Unlike the electrical signals, light signals in one fibre optic do not create interference with light signals in other fibre optic.
  • Thinner: Fibre optic cables are found in less diameter than the copper cables.
  • Ease of Installation: Due to flexibility and thinner size, installation of fibre optic cables is easy as compared to installation of copper cables. Fibre optic cables do not make excessive noise when passing along electric cables.
  • High Bandwidth: Fibre optic cables has high capacity of carrying high bandwidth signals for long distance and do not need repeaters like other cables. Fibre optic cables have bandwidth 400MHz/km while coaxial cable has bandwidth 1 MHz/km.

 

Disadvantages of Fibre Optic Cable

  • High Installation Cost: Installation cost of fibre optic cable, interfaces and cost of transmitters and receivers is much higher.
  • Limited Fibre Optic Power: A limited amount of optic power can be transmitted over fibre optic cable, if we pass excessive amount of power the inner core glass may burst.
  • Unidirectional Transmission: Transmission of signal is unidirectional in fibre optic cable, if we need bidirectional transmission, we need two fibre optic cables.

 

Fiber Optic Cable Connectors

Connector Type Coupling Type Fibre Application
ST Twist on Single/Multimode LANs
FC Screw on Single/Multimode Telecommunications
SC Snap on Single/Multimode CAT5Test Equipment
LC Snap on-RJ-45 Single/Multimode Gigabit Ethernet
MU Push/Pull Single/Multimode Medical/Military Equipment
MT-RJ Snap on-RJ-45 Single/Multimode Gigabit Ethernet/ATM
MPO Push/Pull Single/Multimode Transceivers

 

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