TRANSMISSION TRANSMISSION MEDIAMEDIA

Fiber Optic CableFiber Optic Cable

Fiber Optic CableFiber Optic Cable Fiber-optic cables are composed of a glass or plastic Fiber-optic cables are composed of a glass or plastic

inner core surrounded by cladding, all encased in an inner core surrounded by cladding, all encased in an outside jacket. outside jacket.

Fiber-optic cables carry data signals in the form of Fiber-optic cables carry data signals in the form of light. The signal is propagated along the inner core by light. The signal is propagated along the inner core by reflection.reflection.

Relatively new transmission medium used by Relatively new transmission medium used by telephone companies in place of long-distance trunk telephone companies in place of long-distance trunk lines.lines.

Also used by private companies in implementing local Also used by private companies in implementing local data communications networks.data communications networks.

Require a light source with injection laser diode (ILD) Require a light source with injection laser diode (ILD) or light-emitting diodes (LED).or light-emitting diodes (LED).

plastic jacket glass or plasticcladding

fiber core

Fiber Optic LayersFiber Optic Layers

consists of three concentric sectionsconsists of three concentric sections

Refraction

Critical Angle

Reflection

Refraction & ReflectionRefraction & Reflection

Fiber Optic TypesFiber Optic Types Signal propagation in optical fibers can be Signal propagation in optical fibers can be

multimode (multiple beams from a light source multimode (multiple beams from a light source moves through different path) or single-mode moves through different path) or single-mode (essentially one beam from a light source). (essentially one beam from a light source).

Multimode step-index fiberMultimode step-index fiber In multimode step-index propagation, the core In multimode step-index propagation, the core

density is constant and the light beam changes density is constant and the light beam changes direction suddenly at the interface between the direction suddenly at the interface between the core and the cladding.core and the cladding.

Multimode graded-index fiberMultimode graded-index fiber In multimode graded-index propagation, the core In multimode graded-index propagation, the core

density decreases with distance from the center. density decreases with distance from the center. This causes a curving of the light beams.This causes a curving of the light beams.

Single mode fiberSingle mode fiber•This uses step-index fiber and a highly focused source of light This uses step-index fiber and a highly focused source of light •Has very low density,which make c=90,so beam becomes almost Has very low density,which make c=90,so beam becomes almost horizontal.horizontal.

fiber optic multimodestep-index

fiber optic multimodegraded-index

fiber optic single mode

Fiber Optic SignalsFiber Optic Signals

Fiber Optic AdvantagesFiber Optic Advantages Higher transmission rate of 100Mbps.Higher transmission rate of 100Mbps. It supports voice,video and data.It supports voice,video and data. Greater capacity (bandwidth of up to 2 Greater capacity (bandwidth of up to 2

Gbps).Gbps). Smaller size and lighter weightSmaller size and lighter weight Lower attenuationLower attenuation Immunity to environmental interferenceImmunity to environmental interference Highly secure , it is almost impossible to Highly secure , it is almost impossible to

tap into a fiber cable.tap into a fiber cable. Safe and easy installation.Safe and easy installation. More compact & lighter than copper wireMore compact & lighter than copper wire

Fiber Optic Fiber Optic DisadvantagesDisadvantages

expensive over short distanceexpensive over short distance UnidirectionalUnidirectional requires highly skilled installersrequires highly skilled installers adding additional nodes is difficultadding additional nodes is difficult Maintenance and repairing cost is Maintenance and repairing cost is

high.high.

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