Fiber optic medium

A fiber optic cable consists of a center pure (silica) glass core not much wider than a human hair through which light signals pass. It is surrounded by a glass cladding. sometimes the cladding is surrounded by PVC to increase the cable strength and provide a support for the cladding. The cladding is sometimes surrounded by metal fibers to give extra strength to the cable.

An emitter sends the signals from one end of the cable and a light sensor senses this signals and then converts into its digital equivalent. There is a  transceiver located at both ends of the cable where the signals are converted from electrical to light signals and vice versa. Fiber optic cables are available in different sizes with varying core and cladding diameters but the most commonly used fiber optic cable is the 62.5/125 micrometer. The diameter of the core is 62.5 micrometer and that of the cladding is 125 micrometer. Almost all network technologies that use fiber optic cable require pair of fibers to create the popular fiber optic cabling.


Categories of fiber optic cables

  • Signal Mode :- A type of cable that has only a single strand of glass fiber with a thin diameter. This is a 9/125 micrometer fiber cable. The diameter of the core-glass is approximately 9 micrometer. only a single light attenuation than multi mode fiber thus more information can be transmitted over long distances, increasing speed of transmission.  Fiber optical that use laser are known as single mode cable.


ADVANTAGE  Single mode fiber optic cable id that data can be transmitted at higher speed. Single mode fiber can also transmit data over longer distance, than 1 km as compared to multi mode cables. 

DISADVANTAGE Single mode fiber are that only one signal can be transmitted through it. To transmit two signals you need two stands of fiber optical cable.

  • Multi-Mode :- A type of cable that contains a glass fiber with a larger diameter. Multiple modes of light signals can be propagated through it. This is a 62.5/125 micrometer fiber cable. Light signals are transmitted into the fiber using different path and wavelengths.  Multi mode fiber transmits the data over short distances as the various modes tend to spread over long distances. Resulting in attenuation. Fiber-optical cables that use LEDs are known as multi mode cables.


ADVANTAGE This type of cable is that you can transmit two or more signal using a signal fiber. 

DISADVANTAGE  This type of cable is that data can not be transmitted over long distances using this cable. Since two or more signals are transmitted using one fiber, the transmission speed is less as compared to single mode fiber optic cables.


A connector is a mechanical device that is attached to fiber optic cable or the light source. A number of connectors are used to connect fiber cables. The connectors used with these cables depend on the different kinds of light emitting sources such as lasers and LEDs as well as the different types of light sensors used. The primary types of connectors used with these cables :-

  • Straight tip (ST) :-  It was developed by AT & T. A popular connector used with fiber cable and used in gigabit Ethernets or backbone. Joins individual fiber to optical device. ST can be used for both single and multi mode fibers. It is easy to insert  and remove this connector from the fiber. There are two type of connectors ST and ST-ll. It is similar to BNC T connector. 


  • Sub Miniature Type a (SMA)  :- Defines a connector that uses two individual connectors for each fiber strand. SMA looks similar to the ST but user a threaded outer shell. This type of connection is more rugged, particularly under the stress of vibrations. SMA’s are available in two versions – 905 and 906.

  • Subscriber/Standard connector (SC) :- A type of low cost connector used in 100 Base- FX fiber optic networks and it can be pushed into the device and can be removed by pulling out. It is a one piece component with two slots in it to attach two fiber to send and receive signals. It is similar to the video or audio plug. The SC connector is smaller than the ST and sub miniature type A (SMA) connectors and is about the same size as an RJ45 UTP connector.