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Optical Fiber

ClassificationCan be classified in a number of waysOn the basis of manufacturingSingle component/Multi componentGlass core glass clad

Doped silica core clad

All plastic fiber

On the basis of profile

Step indexMulti mode

Mono mode

Graded index

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Multi Mode Step IndexMade up of glass or doped silica

Reasonably large core diameter and NA to

facilitate efficient coupling of incoherent lightPerformance characteristics vary widely

depending upon material used in fabrication

Structure

Core diameter: 50 to 400 mClad diameter: 125 to 500 m

Buffer jacket diameter: 250 to 1000 m

Numerical Aperture: 0.16 to 0.5

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Multi Mode Step IndexPerformance characteristics

Attenuation Approx 2.5 to 50 dB/Km @ 0.85 m wavelength

40 dB/Km for glass fiber

5 dB/Km for doped silica fiber

0.4 dB/Km @ 1.3 m wavelength

Bandwidth 6 to 50 M Hz Km

Application Short haul communication

Limited bandwidth applications

Relatively low cost applications

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Multi Mode Graded IndexMade up of glass or doped silica

Higher purity level than MMSI fibers

Many different structural profiles developedfor different application

Structure (Typical)

Core diameter: 30 to 100 m

Clad diameter: 100 to 150 m

Buffer jacket diameter: 250 to 1000 m

Numerical Aperture: 0.2 to 0.3

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Multi Mode Graded IndexStructural types

50 /125 m (core-clad) with NA between 0.20 to0.24 recommended by ITU-T for telecomapplications @ 0.85 and 1.3 m wavelength.Now mainly used for Data Links and LANs

65/124 m (core-clad) with NA between 0.26 to0.29 for long distance subscriber loops operating

@ 0.85 and 1.3 m. Now mainly used for LANs100/125 m (core-clad)with NA of 0.29. High

coupling efficiency with LEDs operating @ 0.85m. Used in low cost, short distance applications

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Multi Mode Graded IndexPerformance characteristics

Attenuation Approx 2 to 10 dB/Km @ 0.85 m wavelength

0.4 dB/Km @ 1.3 m and 0.25dB/Km @1.55 m

Bandwidth 300 to 3 GHz-Km

ApplicationMedium haul communication

Medium to high bandwidth applications

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Single Mode Step IndexMade up of doped silica

Small core diameter

StructureCore diameter: 5 to 10 m

Clad diameter: Generally 125m

Buffer jacket diameter: 250 to 1000 m

Numerical Aperture: 0.08 to 0.15 (usuallyaround 0.1)

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Single Mode Step IndexPerformance characteristics

Attenuation Approx 2 to 5dB/Km @ 0.85 m wavelength

BandwidthGreater than 500MHzKm

Theoretically 40GHzKm @ 0.85 m

Practical bandwidth of 10GHzKM @ 1.3 m

Application Long haul communication

Excessive bandwidth applications

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Plastic Clad FibersMultimode fibers with both step and graded

profiles

Glass core and plastic clad (often siliconrubber)

Lower induced radiation losses (improvedperformance under certain environments)

Slightly cheaperStructure SI GICore diameter: 100 to 500 50 to

100 m

Clad diameter: 300 to 800 125

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Plastic Clad FibersPerformance CharacteristicsStep Index: 5 to 50 dB/Km

Graded index: 4 to 15 dB/Km

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Optical Fiber CableWhy we need cabling

Unprotected optical fiber has many

disadvantagesPoor strength and stability

Brittle and small cross sections are susceptibleto damage during laying

Hence cabling is done to improveFiber protection Fiber damage and breakage during installation and

throughout life

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Optical Fiber CableCable strength Should have similar mechanical properties as of

electrical cables

Increase in resistance to mechanical stress, strainand adverse environmental condition

Squeezing and vibrations

Identification of joints

Stability Reduction of micro bending due to environmental

conditions specially temperature

Reduction in hydrogen absorption and nuclear

radiation exposure