Fiber Types

There are two type of fibers

1. Multimode Fiber
2. Monomode Fiber   

Multimode Fiber

                                                          Core:50μm   
                                                          Cladding:125μm          

                                                                 50/125μm

                                                              Core:62.5μm
                                                              Cladding:125μm

                                                               62.5/125μm


Multimode fiber has two types 

1.  Step Index
2. Graded Index

Graded Index
                       
                          In this type of fiber,there is no step change of refractive index between core and the cladding.The core has a refractive indexthat gradually decreases  from the center to out words  to outer surface of fiber.

                            The rays close to the center are slowed down because they travel smaller distance.The rays tarveling away from the axis are speed up using law refractive index than the center.There for they can catched up.Now all the rays will arrive at nearly same times at  the Rx end.There for law dispersion-end  high band width is achieved.Graded index just help to all the rays with entered to fiber with any angle through acceptance cone.


 Monomode Fiber
                  To minimize dispersion we can reduce core diameter to very small valuves such as 5-10 μm 

                                                      
                                                     How ever cast of mono-mode fiber high due to manufacturing difficulties.For a multimode fiber 'NA' is between 0.2-0.3.But in a mono-mode fiber 'NA' is approximately 0.1 there for NA help us to identify the capability of the fiber.When the 'NA' is low the fiber is capable of transmitting higher bit rates. 

Fiber Construction

                                                                                                                                             










                                                                                                                                                                                                                                                                                        These photos showing the cross section of fiber cable. 






  Three types of fiber construction

• PCP:Plastic Cladding with Plastic Core
• PCS:Plastic Cladding with Glass Core
• SCS:Glass Cladding with Glass Core 

 Fiber Materials 
     
Core 

• Glass: Doped silica
• Plastic: Polystyrene  ,Polymethylmathaccrillic 

Cladding

• Glass:Doped silica
• Plastic:Silicon,Teflon 

                  

  
 

Introduction

In the past the light was used only to see things but not to communicate.Now we know that use of optical(light) waves can carry large amount of information.The air(Atmosphere) is not a very good transmission medium for optical communication.There are many reason for make signal attenuate..optical communication become a reality with the development of optical fibers.The optical fiber communication belongs to the category of wired communication.To carry this optical frequencies over long distance we need a guiding device.This device is the optical fiber.