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Optical Fiber ClassificationCan be classified in a number of waysOn the basis of manufacturing

Single component/Multi component Glass core glass clad Doped silica core clad All plastic fiber

On the basis of profileStep index

Multi mode Mono mode

Graded index

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Multi Mode Step IndexMade up of glass or doped silicaReasonably large core diameter and NA to facilitate

efficient coupling of incoherent lightPerformance characteristics vary widely depending upon

material used in fabricationStructure

Core diameter: 50 to 400 µmClad diameter: 125 to 500 µmBuffer jacket diameter: 250 to 1000 µmNumerical 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 µm wavelength 40 dB/Km for glass fiber 5 dB/Km for doped silica fiber 0.4 dB/Km @ 1.3 µm 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 silicaHigher purity level than MMSI fibersMany different structural profiles developed for different

applicationStructure (Typical)

Core diameter: 30 to 100 µmClad diameter: 100 to 150 µmBuffer jacket diameter: 250 to 1000 µmNumerical Aperture: 0.2 to 0.3

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Multi Mode Graded IndexStructural types

50 /125 µm (core-clad) with NA between 0.20 to 0.24 recommended by ITU-T for telecom applications @ 0.85 and 1.3 µm wavelength. Now mainly used for Data Links and LANs

65/124 µm (core-clad) with NA between 0.26 to 0.29 for long distance subscriber loops operating @ 0.85 and 1.3 µm. Now mainly used for LANs

100/125 µm (core-clad)with NA of 0.29. High coupling efficiency with LEDs operating @ 0.85 µm. 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 µm wavelength 0.4 dB/Km @ 1.3 µm and 0.25dB/Km @1.55 µm

Bandwidth 300 to 3 GHz-Km

Application Medium haul communication Medium to high bandwidth applications

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Single Mode Step IndexMade up of doped silica Small core diameterStructure

Core diameter: 5 to 10 µmClad diameter: Generally 125µmBuffer jacket diameter: 250 to 1000 µmNumerical Aperture: 0.08 to 0.15 (usually around 0.1)

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Single Mode Step IndexPerformance characteristics

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

Bandwidth Greater than 500MHzKm Theoretically 40GHzKm @ 0.85 µm Practical bandwidth of 10GHzKM @ 1.3 µm

Application Long haul communication Excessive bandwidth applications

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Plastic Clad FibersMultimode fibers with both step and graded profilesGlass core and plastic clad (often silicon rubber)Lower induced radiation losses (improved performance under

certain environments)Slightly cheaperStructure SI GI

Core diameter: 100 to 500 50 to 100 µmClad diameter: 300 to 800 125 to 150 µmBuffer jacket diameter: 500 to 1000 250 to 1000 µmNumerical Aperture: 0.2 to 0.5 0.2 to 0.3

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Plastic Clad FibersPerformance Characteristics

Step Index: 5 to 50 dB/KmGraded index: 4 to 15 dB/Km

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Optical Fiber CableWhy we need cablingUnprotected optical fiber has many disadvantages

Poor strength and stabilityBrittle and small cross sections are susceptible to damage

during layingHence cabling is done to improve

Fiber 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, strain and adverse

environmental condition Squeezing and vibrations

Identification of jointsStability

Reduction of micro bending due to environmental conditions specially temperature

Reduction in hydrogen absorption and nuclear radiation exposure