Fiber Optic

Optical fiber 

Transmission media are the physical way that  device can connect on network, Transmission media divided into two parts wired and wireless.each of them have its on types 

The optical fiber or fiber optic is one of the most popular and used for transferring data throw content  

Optical Fiber Anatomy 

Core:  The glass or plastic center of an optical fiber. 

Cladding: Glass or plastic surrounding the core of an optical fiber; the optical density of the cladding must be less than that of the core.

Optical fibers use reflection to guide light through a channel. The difference in density of the two materials must be such that a beam of light moving through the core is reflected off the cladding instead of being refracted into it. 

The composition of a typical fiber-optic cable

The outer jacket is made of either PVC or Teflon. Inside the jacket are Kevlar strands to strengthen the cable. Kevlar is a strong material used in the fabrication of bulletproof vests. Below the Kevlar is another plastic coating to cushion the fiber. The fiber is at the center of the cable, and it consists of cladding and core.

Propagation mode:

Multimode:

In fiber optics technology multimode fiber is used for signal transmission for short distances. light waves dispersed into many paths as they goes through the cable's core.

Single-mode:

In fiber optics technology single mode fiber is one of two types of fiber currently in use. It is a single strand of glass fiber for a single ray (or mode).of light transmission. Single mode fiber is used for long distance transmission.

Multimode has two types : 

step-index: Single mode optical fiber with a uniform refractive index throughout the core. The step is the shift between the core and the cladding, which has a lower refractive index. 

graded-index:Contains a core in which the refractive index diminishes gradually from the center axis out toward the cladding. The higher refractive index at the center makes the light rays moving down the axis advance more slowly than those near the cladding. Due to the graded index, light in the core curves helically rather than zigzag off the cladding, reducing its travel distance. The shortened path and the higher speed allow light at the periphery to arrive at a receiver at about the same time as the slow but straight rays in the core axis. The result: digital pulse suffers less dispersion. This type of fiber is best suited for local-area networks. 

Advantage

-Higher bandwidth, less signal attenuation, Immunity to electromagnetic interference, Resistance to       corrosive materials

-Light weight, Greater immunity to tapping.

Disadvantage

-Installation and maintenance, Unidirectional light propagation, 

-Cost