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Muhammad Awais Ali UW-11-EE-BSc-12Sikandar sittar UW-11-EE-BSc-76Faraz Hussain UW-11-EE-BSc-64Ali Raza UW-11-EE-BSc-08Saac Aurangzab UW-10-EE-BSc-50

Group Members

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TopicOptical Fiber

Communication

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IntroductionTransmission Media

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Introduction• Communications systems that carry information through a

guided fiber cable are called fiber optic systems.

• Use of optical fibers to replace conventional transmission lines and microwave wave-guide in telecommunication systems.

• Light is effectively the same as RF radiation but at a much higher frequency, theoretically the information-carrying capacity of a fiber is much greater than that of microwave radio systems.

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• As they are not electrically conductive, hence very suitable for use in areas where electrical isolation and interference are severe problems.

• An attenuation of less than 2dB/Km.

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Advantages of Optical Communications1) Extremely wide system bandwidth

- up to 10 GHz is possible

2) Immunity to EMI - such as lightning, electric motors, fluorescent lights

3) Virtual elimination of cross-talk

4) Lower signal attenuation than other propagation systems

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Advantages of Optical Communications5) Lighter weight and smaller size

6) Lower cost

7) Conversion of the earth’s resources - principal ingredient in glass is sand which is cheap and virtually unlimited supply

8) Safety - no hazard of short circuits nor spark will exist in optical fiber

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Fundamentals of Fiber Optic Systems

• Optical fibers guide light waves within the fiber material because light rays bend or change direction when they pass from one medium to another. This phenomenon is called reflaction.

• Optical fiber is a thin, transparent strand of material, usually glass or plastic or a combination of the two, that is used to carry light beams.

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Reflection in Optical Fiber• 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.

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Refraction of Light• Light travels at

approximately 3x108 m/s in free space and slower in a material denser than free space. This reduction in speed as it passes from free space into a denser material results in refraction of the light.

• Sshows the light is bent at the interface. The degree to which the ray is bent depends on the index of refraction n of the denser material.

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Physics of Light• The normal is an imaginary line

perpendicular to the interface of the 2 materials.

• The angle of incidence is the angle of incident ray to the normal.

• The angle of refraction is the angle of refracted ray to the normal.

• The critical angle is the angle of incidence that will produce a 900 angle of refraction.

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• 3 specific conditions are shown in Fig. The angle of incidence, A1 and the angle of refraction, A2.

• Material 1 is more dense than material 2, so n1 is greater than n2.

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• Fig. 3A shows how a light ray passing from material 1 to material 2 is refracted in material 2 when A1 is less than the critical angle.

• Fig. 3B shows the condition that exists when A1 is at the critical angle and angle A2 is at 900. The light is directed along the boundary between the 2 materials.

• Fig. 3C shows that any light ray incident at an angle greater than A1 of Fig. 3B will be reflected back into material 1 with A2 equal to A1.

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Applications include TelephonesInternetLANs - local area networksCATV - for video, voice and Internet connectionsUtilities - management of power gridSecurity - closed-circuit TV and intrusion sensorsMilitary - everywhere!

Fiber Optic Communications

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Why Use Fiber Optics?

• Economics• Speed• Distance• Weight/size• Freedom from interference• Electrical isolation• Security

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Total Internal Reflection of LightTotal internal reflection in optical fibers

• Total internal reflection forms the basis for light propagation in optical fibers.

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Fiber construction

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Fiber Optic Applications

• Fiber is already used in:– > 90% of all long distance telephony– > 50% of all local telephony– Most CATV networks– Most LAN (computer network) backbones– Many video surveillance links

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Fiber Optic Applications

• Fiber is the least expensive, most reliable method for high speed and/or long distance communications

• While we already transmit signals at Gigabits per second speeds, we have only started to utilize the potential bandwidth of fiber

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Light Used In Fiber Optics

• Fiber optic systems transmit using infrared light, invisible to the human eye, because it goes further in the optical fiber at those wavelengths.

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Propagation modes

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Mode of Propagation

• Mode simply means path from which light is propagated.

• If there is only one path for light to take down the cable, it is called single mode.

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

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Modes

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Fiber types

LOSSES OF POWER

1.Power Loss By Scattering And Absorption.

2.Power Loss Due To The Dispertion Or Scattering

Any Question??????

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Thanks

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