Signal attenuation and distortion presentation optical fiber communication

1. Introduction
 A waveguide is a structure that guides waves, such as electromagnetic or
microwave waves.
 Example: In water pipe, pipe is guiding water to its destination
 An optical wave guide is a cylindrical dielectric wave guide capable of confining and
guiding light waves.

2. Optical fibre structure
This has three elements
 Core (inner layer)
 Cladding (middle layer)
 Buffer (outer layer)

3. Types of Optical Fibre
waveguide
Mode based
Materials based
Refractive Index based

4. Mode based
This classification is based on the mode of propagation of light
 Single mode: This has only one single fundamental ray propagating in a
fibre.
 Single mode fibre has core diameter of 8 to 10 micro-meter and cladding
thickness of 125 micro-meter.
 These have high bandwidth and are used for data transmission in long
distances.
 These have no degradation and low dispersion

5.  Multi mode: This supports many propagating rays through fibre.
 Multi mode fibre has core diameter of 50-200 micro-meter and cladding
thickness of 125-400 micro-meter.
 These have limited bandwidth and are inexpensive
 These are used for data transmissions in short distances.
 These have high capacity and reliability.
 Multi-modes are also used when there is high optical power transmission
like laser welding.

6. Material based
Optical fibres can be classified based on core and cladding materials into
three types
 Glass core and cladding
 These have low attenuation and best propagation characteristics.
 These are delicate to handle
 Glass core and Plastic cladding
 These have medium attenuation and propagation characteristics.
 These are more uneven.

7.  Plastic Core and Cladding
 Polymethylmethacrylate is used for core.
 These have very high attenuation.
 These can be installed very easy and inexpensive.
 These are more flexible and uneven.

8. Refractive index based
Optical fibre can also be classified based on refractive index profile.
 Step-index: Refractive index is uniform and makes a step change at core-
cladding interface.
 Graded-index: These do not have a constant refractive index in the core,
but the index decreases from centre and these are inhomogeneous fibres.

9. Step index
 This can be further classified as step index single mode and multi mode.
 Low data rate and band width
 That ray path of light is in zig-zag manner
 Uniform core refractive index which is also high
 Step index fibres diameter of core is 50-200 micro-meters for multi mode and 10
micro-meters for single mode
 Used in application of local network
communications.

10. Graded index
 Multi-mode is the only type of graded index fibre.
 These have low attenuation with high band width.
 The ray path of light propagation is helical in manner.
 Refractive index at core is non uniform.
 These are best suited for medium to high bandwidth applications.
 Mostly used in local and wide area networks.

11. Thank You