Fibre Optics 2

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FIBRE OPTICS

COMMUNICATION

PRESENTED BY :-AJAY RANA

B.TECH 3RD YEAR

ROLL NO. 0803231011



INTRODUCTION

� Fiber-optic communication is a method of transmitting information fromone place to another by sending pulses of light through an optical f ibre.

� The light forms an electromagnetic carrier wave that is modulated to carryinformation.

� First developed in the 1970s, f iber-optic communication systems haverevolutionized the telecommunication industry and have played a major role inthe advent of the information age.

� The process of communicating using f iber-optics involves the following basic steps:

a. Creating the optical signal involving the use of a transmitter,

b. Relaying the signal along the f iber,

c. Ensuring that the signal does not become too distorted or weak,

d. Receiving the optical signal,

e. Converting it into an electrical signal.



What are Fiber Optics?

Fiber optics (optical f ibers) are long, thin

strands of very pure glass about the

diameter of a human hair. They are

arranged in bundles called optical

cables and used to transmit light signalsover long distances.



Optical Fiber

� Core

± Glass or plastic with a higher index of

refraction than the cladding

± Carries the signal

� Cladding

± Glass or plastic with a lower index of

refraction than the core

� Buffer

± Protects the f iber from damage and

moisture

� Jacket

± Holds one or more f ibers in a cable





� Fig. 3A shows how a light ray passing from material 1 tomaterial 2 is refracted in material 2 when A1 is less than thecritical angle.

� Fig. 3B shows the condition that exists when A1 is at thecritical angle and angle A2 is at 900. The light is directedalong the boundary between the 2 materials.

� Fig. 3C shows that any light ray incident at an angle greaterthan A1 of Fig. 3B will be reflected back into material 1 withA2 equal to A1.

Physics of Light



Fig 1: Fiber for light beam propagation

Reflection in Optical Fiber



� From fig. 1, the light rays are reflected from the

inner walls as they propagate lengthwise along the

fiber.

� A single light beam can be modulated

simultaneously by hundreds, or even thousands, of

independent signals.

Reflection in Optical Fiber



Total internal reflection in optical fibers

� Total internal reflection forms the basis for lightpropagation in optical fibers.

Total Internal Reflection of Light



� Mode simply means path from which light ispropagated.

� If there is only one path for light to take down thecable, it is called single mode.

� If there is more than one path, it is called multi-mode.

Mode of Propagation







� The light rays that strike the core/cladding interface at anangle greater than the critical angle are propagated downthe core in a zigzag fashion, continuously reflecting off theinterface boundary.

� There are many paths that a light ray may follow as itpropagates down the fiber. As a result, all light rays do notfollow the same path and hence do not take the sameamount of time to travel the length of the fiber.

Multi-mode Step-Index Fiber





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Advantages of f iber optics

Much Higher Bandwidth (Gbps) - Thousands of channels can be

multiplexed together over one strand of f iber

Immunity to Noise - Immune to electromagnetic interference (EMI).

Safety - Doesnt transmit electrical signals, making it safe inenvironments like a gas pipeline.

High Security - Impossible to tap into.

Less Loss - Repeaters can be spaced 75 miles apart (f ibers can be made

to have only 0.2 dB/km of attenuation)

Reliability -More resilient than copper in extreme environmentalconditions.

Size - Lighter and more compact than copper.

Flexibility - Unlike impure, brittle glass, f iber is physically very flexible.

.





Present Telecommunications

Internet Access

Cable and Satellite Television

Decorative Light Source



Optical Fibre In Telecommunication

BSNL has the largest optical f ibre cable network in the country,

comprising at least 600,000 route kilometres covering all state

capitals and district headquarters. The f irm also operates around

42,000 telecom towers.

Tata Teleservices plans to spend Rs.2 billion to raise its optical

f ibre network to 5,000 km in the east byMarch 2006, the company.

Reliance fully-owned subsidiary of the his Industries, will lay a

4000 route km optical f iber network in Uttar Pradesh, investing 40

billion.





The Internet



THANK YOU

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Fibre Optics 2