Preparation of Optical Fiber

As many other processes the outside vapour phase oxidation(OVPO) is used to prepare both the step and the graded index fiber. The SiCl4 and GeCl4 in the gaseous stage are mixed Oxygen to obtain pure SiO2 as given by the following reactions.

SiCl4+2H2O=SiO2+(HCl)
i.e,vapour +gas=solid+gas


GeCl4+O2=Geo2+2Cl2
i.e,vapour+gas=solid+gas

The mixture of Sio2 and GeO2 is then passed through a burner so that a layer of this mixtur is deposited on a cool rotaing mandrel.

The burner is moved back and forth over the lenght of the mandrel dto deposit approximately 200 layer sothe mixture.The amount of GeO2 is not changed untl the core calddding interface is reached to prepare a step index fiber,whereas it is gradulally changed at the completion of each travers of the burner for preparing a graded index fibre. In this process ,SiO2 is the base material and GeO2 is the dopant.

The compounds such as P2O5 and F can also be used as dopants.After depositing the required number of layers, the mandrel is remover and the central hole is collapsed.The resulted shape of the mixture is called the preform. It is possible to draw a biber of lenght around 10km eith 120 micro meter cor in diameter.
The mixture from which the fiber is prepared is usually denoted by single symbol such as GeO2-SiO2 in this case, which is read as SiO2(Silica glass) dopped with Ge2.

types of optical fiber

Step indes fiber:
An optical fiber with a core of constant refractive index(n1) and a cladding of slightly lower refractive indes(n2) is known as the step index fiber.A term 'step' is given because the refractive index profile for this type of fiber makes a step change at the cor-cladding interface. All the fibers considered so far are therefore the step index fiber.

Graded indes fiber:
The optical whose refractive index is maximum n1 at the axis and gradually decreases with the radial distance from the axis to a xonstant refractive index n2 the caldding is known as the graded index fiber.The profile parameter alpha condtrols the profile i.e shape of the refractive indes of core of the fiber. Although an infinite number of profiles can be obatined with different values of alpha, only the step.

Uses of optical fiber

Uses of optical fiber

1. Audio/Video:In optical fibers we can send the huge amount of signals including audio and video signals.
   
2. Networking:Likewise,in the field of networking it plays the vital role . Because,since it has a higher bandwidth ranging from GHz-THz.

Advantages

optical fiber advantages

1. Greater bandwidth
2. Bandwidth raises from GHZ -THz
3. Less attenuation
4. Secured data propagation
5. Highly sealed data and higly protected from outer climate.
6. Data propagate with the velocity of light.
7. Data propagation is fast than the other.
8. Highly reliable the the other comminication media.
   

Drawbacks of optical fiber

Drawbacks:
while talking about the advantages and drawbacks of optical fiber it quite expensive in joining the terminals of optical fibers end to end.Till today record joining the optical terminal end to end are even done underneath the ocean.Such joining fibers are called splicing. And there are many kinds of splicing .

And the another things i.e drawbacks is the form and the structures of optical fiber may be bended hazardously of it may be even break as well while undergroundig the optical fibers. So, in case of such things optical fibers should be hold with great care.

Total Internal Reflection

Total Internal Reflection:

In optical fiber the one of the main thing to be understood is the way of occuring the total internal reflection.

Mainly, the total internal reflection is occured when the light passes from rarer medium to
denser medium. It is occured when the incident angle is greater than the critcal angle.When such phenomena is possible then occurence of total internal reflection is possibled.But if the incident angle is less than critical angle in the denser medium then possibility of occuring total internal reflection is far less.

Therefore,to transfer or propagate the data through optical medium total internal reflection plays vital role.

Physical structure of optical fiber

Physical structure:

Optical fiber is buit of via of three layers inclu
ding internal,middle and outer layers respectivelym.

1. Internal :-It's the one of the main core innings through which the main signal is transferred in the form of light occuring total internal reflection.Data send is propagate in the form of light.
2. Middle:-The secondary one is cladding.It is the secondary part through which data transferred is made safe and helps to minimizes the attenuation.
3. Outer:-It's the one of the outermost part of optical cable which is callled as the Jacket layer.It is one of the protecting layer which saves the datas from wheather, climate and other external calamities.
   

INTRODUCTION

Optical Fiber
In theory, the greater the carrier frequency, the larger the available transmission bandwidth and thus the information-carryaing capacity of the communication systyem. For this reason radio communication was developed to higher frequencies(i.e VHF and UHF) leading to the introduction of the even higher frequency microwave and latterly, millimetre wave transmission.It may be also be noted that communicatio at opica frequencies offers an increase in the potential usable bandwidth by factor of around 10000 over high frequency microwave transmission.

Until 1966 when Kao an Hockham and Werts simultaneously brought the proposals for optical communication via dielectric waveguides or optical fiber the optical communication was carried out through free space using fires, reflecting mirrors,and signaling lamps.The main drawback of free sapce opical communication is the degradation of the optical signal by distrurbances such as rain ,snow,fog,dust and atmospheric turbulence.the optical communication via fibre which is now popularly termed as the optical fiber communicationn has overcom this drawback. The information source provides an electrical signal, which drivers an optical source to give modulation of the lightwave carrier. Th optical source,which provides the electrical- optical conversion may be either a semiconductor lase or light emittin diode(LED) . The transmission medium consists of an optical fiber cable. The optical detector proveids demodulation aof the optical carreir. the optical detector, which provides optical-electrical conversion,may be a photodiode or a phototransistor.The optical carrier may be modulated using either an analog aor digital signal.

Science is to know the fact information. Information technology and advanced devices has brought out immense changes in the world. So, as a development of technology optical fiber has played one of the big role in the field of information technology.Optical fiber has won the over the technology of co-axial cables and twisted cable respectively.

Defination:
Optical word comes from the optics,which means light.It is a kind of glass through which data is transferred in the form of light occuring total internal reflection.
Optical fiber is one of the best technology till now which has following advantages:

1. Enormous/Higher potential bandwidth .



2. No repeaters is needed from 30km-80km.



3. Attenuation is minimum.



4. Transferring the data in the high speed.



5. Data is secured and no losses of datas.



6. Small/size and weight.



7. Electrical isolation.



8. Immunity to interference.



9. Signal security.



10. Low transmission loss.



11. Ruggeddness and flexibility.



12. System reliability and ease of maintenace.



13. Potential low cost.