Fiber Optic Cable

(Communication Terms – Applications – Advantages & Disadvantages)

Definition

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

 

Types of Fiber 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).

Fiber 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 fiber connector. Expressed in negative dB relative to incident power.

Bandwidth: The range of signal frequencies that a fiber optic cable will transmit.

Buffer: Protective coating over the fiber.

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 fiber optic cable where the core diameter is much larger than the wavelength of light being transmitted. Two common multimode fiber 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 fiber. 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 fiber 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: Fiber 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 fiber optic cables for wiring HDTV, CATV, video on-demand, internet and other applications.

Advantages of Fiber Optic Cable

Less Expensive: For long distance transmissions, fiber optic cable is much less expensive than pure copper network cable.

Inflammable: As no electricity passes through fiber optic cable, no fire hazard exists.

Lightweight: Fiber optic cable is much less in weight than the copper cable and it takes less space in the ground.

Digital Signals: Fiber optics are very suitable for transmitting digital information, that’s why fiber optic cables are preferred in computing networks.

Light Signals: Unlike the electrical signals, light signals in one fiber optic do not create interference with light signals in other fiber optic.

Thinner: Fiber optic cables are found in less diameter than the copper cables.

Ease of Installation: Due to flexibility and thinner size, installation of fiber optic cables is easy as compared to installation of copper cables. Fiber optic cables do not make excessive noise when passing along electric cables.

High Bandwidth: Fiber optic cables has high capacity of carrying high bandwidth signals for long distance and do not need repeaters like other cables. Fiber optic cables have bandwidth 400MHz/km while coaxial cable has bandwidth 1 MHz/km.

Disadvantages of Fiber Optic Cable

High Installation Cost: Installation cost of fiber optic cable, interfaces and cost of transmitters and receivers is much higher.

Limited Fiber Optic Power: A limited amount of optic power can be transmitted over fiber optic cable, if we pass excessive amount of power the inner core glass may burst.

Unidirectional Transmission: Transmission of signal is unidirectional in fiber optic cable, if we need bidirectional transmission, we need two fiber optic cables.

Fiber Optic Cable Connectors

Connector Type

Coupling Type

FiberApplication

ST Twist on Single/Multimode LANs

FC Screw on Single/Multimode Telecommunications

SC Snap on Single/MultimodeCAT5

Test Equipment

LC Snap on-RJ-45 Single/Multimode Gigabit Ethernet

MU Push/Pull Single/MultimodeMedical/Military Equipment

MT-RJ Snap on-RJ-45 Single/Multimode Gigabit Ethernet/ATM

MPO Push/Pull Single/Multimode Transceivers