OPTICAL FIBERS: OPTICAL FIBERS: MATERIALS & FABRICATIONMATERIALS & FABRICATION

By By

Dr Neena Gupta Dr Neena Gupta

Asstt. Prof Asstt. Prof

E& EC DepttE& EC Deptt

PEC ,ChdPEC ,Chd

IntroductionIntroduction

Optical fiber communication systems are more advantageous Optical fiber communication systems are more advantageous over metallic communication Systems becauseover metallic communication Systems because

Cost effectiveness & Stable over long distancesCost effectiveness & Stable over long distances

Available in different sizes ,refractive indices, index profiles, Available in different sizes ,refractive indices, index profiles, material and operating wavelength for different system material and operating wavelength for different system applications.applications.

Can be handled in a more efficient manner than conventional Can be handled in a more efficient manner than conventional electrical transmission cables without degradation of the electrical transmission cables without degradation of the characteristics or damage.characteristics or damage.

The fibers and fiber cables may be terminated and connected The fibers and fiber cables may be terminated and connected together (jointed) without excessive practical difficulties.together (jointed) without excessive practical difficulties.

Optical FibersOptical Fibers

An optical fiber contains three layers: An optical fiber contains three layers:

Core - made of highly pure glass with a high refractive Core - made of highly pure glass with a high refractive index for the light to travelindex for the light to travel

Cladding- a middle layer of glass with a lower refractive Cladding- a middle layer of glass with a lower refractive index index

And an outer polymer jacket to protect the fiber from And an outer polymer jacket to protect the fiber from damage. damage.

Optical Fiber Optical Fiber

Types of Optical FiberTypes of Optical Fiber

• On the basis of Refractive IndexOn the basis of Refractive IndexStep Index FiberStep Index FiberGraded Index FiberGraded Index Fiber

• On the basis of ModesOn the basis of ModesSingle mode FiberSingle mode FiberMultimode FiberMultimode Fiber

Optical Fiber Optical Fiber

   Various materials used for making fibersVarious materials used for making fibers

Various methods of preparation for silica based optical fibers (both Various methods of preparation for silica based optical fibers (both liquid and vapour phase) with characteristics suitable for liquid and vapour phase) with characteristics suitable for telecommunication applications.telecommunication applications.

Developments in the area of fiber about polymeric fibers for lower Developments in the area of fiber about polymeric fibers for lower bandwidth, very short haul applications.bandwidth, very short haul applications.

The requirements for optical fiber cabling in relation to fiber protection, The requirements for optical fiber cabling in relation to fiber protection, and and

Finally, cable design strategies and their influence upon typical fiber Finally, cable design strategies and their influence upon typical fiber cable construction.cable construction.

Points to be Discussed

Fiber MaterialsFiber Materials

  In selecting materials for optical fibers, a number of In selecting materials for optical fibers, a number of requirements must be satisfied:requirements must be satisfied:

It must be possible to make long, thin, flexible fibers from the It must be possible to make long, thin, flexible fibers from the material.material.

The material must be transparent at a particular wavelength The material must be transparent at a particular wavelength for the fiber to guide light efficiently.for the fiber to guide light efficiently.

Physically compatible materials having slightly different indices Physically compatible materials having slightly different indices for the core and cladding must be available.for the core and cladding must be available.

Materials satisfying these requirements Materials satisfying these requirements are glasses and plasticsare glasses and plastics

The majority of fibers are made of glass consisting either of silica The majority of fibers are made of glass consisting either of silica (SiO(SiO22) or a silicate.) or a silicate.

The variety of available glass fibers ranges from high-loss glass The variety of available glass fibers ranges from high-loss glass fibers with large cores used for short transmission distances to fibers with large cores used for short transmission distances to very transparent (low loss) fibers employed in long haul very transparent (low loss) fibers employed in long haul applications.applications.

Plastic fibers are less widely used because of their substantially Plastic fibers are less widely used because of their substantially higher attenuation than glass fibers.higher attenuation than glass fibers.

The main use of plastic fibers is in short distance applications and The main use of plastic fibers is in short distance applications and in abusive environments, where the greater mechanical strength of in abusive environments, where the greater mechanical strength of plastic fibers offers an advantage over the use of glass fibers.plastic fibers offers an advantage over the use of glass fibers.

Glass FibersGlass Fibers

Glass is made by fusing mixtures of metallic oxides, sulphides Glass is made by fusing mixtures of metallic oxides, sulphides or selenides. The resulting material is a randomly connected or selenides. The resulting material is a randomly connected molecular network rather than a well defined orderly structure molecular network rather than a well defined orderly structure as found in crystalline materials.as found in crystalline materials.

   The largest category of optically transparent glasses from which The largest category of optically transparent glasses from which

optical fibers are made consists of the oxide glasses. Of these, optical fibers are made consists of the oxide glasses. Of these, the most common is silica, which has a refractive index of 1.458 the most common is silica, which has a refractive index of 1.458 at 850 nm. at 850 nm.

To produce two similar materials having slightly different To produce two similar materials having slightly different indices of refraction for the core and cladding, either fluorine or indices of refraction for the core and cladding, either fluorine or various oxides (referred to as dopants) such as Bvarious oxides (referred to as dopants) such as B22OO33, GeO, GeO22 or or PP22OO55 are added to the silica. The addition of GeO are added to the silica. The addition of GeO22 or P or P22OO55 increases the refractive index whereas doping the silica with increases the refractive index whereas doping the silica with fluorine or Bfluorine or B22OO33 decreases it. decreases it.

Since the cladding must have a lower index than the core, Since the cladding must have a lower index than the core, examples of fiber composition are:examples of fiber composition are:

1.1. GeOGeO22 – SiO – SiO22 core; SiO core; SiO22 cladding cladding

2.2. PP22OO55 – SiO – SiO22 core; SiO core; SiO22 cladding cladding

3.3. SiOSiO22 core; B core; B22OO33 – SiO – SiO22 cladding cladding

4.4. GeOGeO22 – B – B22OO33 – SiO – SiO22 core; B core; B22OO33 – SiO – SiO22 cladding cladding

Here the notation GeOHere the notation GeO22 – SiO – SiO22, e.g., denotes a GeO, e.g., denotes a GeO22 doped silica doped silica glass.glass.

The principle raw material for silica is sand. Glass composed of The principle raw material for silica is sand. Glass composed of pure silica is called pure silica is called silica glass, fused silicasilica glass, fused silica, or , or vitreous silicavitreous silica. . Some of its desirable properties are:Some of its desirable properties are:

A resistance to deformation at temperatures as high as 1000A resistance to deformation at temperatures as high as 1000ooC.C.

A high resistance to breakage from thermal shock because of its A high resistance to breakage from thermal shock because of its low thermal expansion.low thermal expansion.

Good chemical durability, and high transparency in both the Good chemical durability, and high transparency in both the visible and infrared regions of interest to fiber optic visible and infrared regions of interest to fiber optic communication systems.communication systems.

Its high melting temperature is a disadvantage if the glass is Its high melting temperature is a disadvantage if the glass is prepared from the molten state. This problem is partially prepared from the molten state. This problem is partially avoided when using vapour deposition techniques.avoided when using vapour deposition techniques.

Fluoride glasses have extremely low transmission losses at Fluoride glasses have extremely low transmission losses at mid infrared wavelengths (0.2 to 8 mid infrared wavelengths (0.2 to 8 μμm) with the lowest loss m) with the lowest loss being around 2.55 being around 2.55 μμm. m.

Heavy metal fluoride glass, which uses ZrFHeavy metal fluoride glass, which uses ZrF44 as a major as a major component and glass network former. component and glass network former.

Moderate resistance to crystallization by adding more Moderate resistance to crystallization by adding more constituents such as ZBLAN (after its elements ZrFconstituents such as ZBLAN (after its elements ZrF44, BaF, BaF22, LaF, LaF33, , AlFAlF33 and NaF), as shown in table.This material forms the core of and NaF), as shown in table.This material forms the core of the glass fiber. the glass fiber.

To make a lower refractive index glass, one partially replaces To make a lower refractive index glass, one partially replaces ZrFZrF44 by HaF by HaF44 to get a ZHBLAN cladding. to get a ZHBLAN cladding.

MATERIAL MOLECULAR %age

ZrF4 54

BaF2 20

LaF3 4.5

AlF3 3.5

NaF 18

Halide Glass Fiber

Ultra pure materials must be used to reach this low loss level. Ultra pure materials must be used to reach this low loss level.

Fluoride glass is prone to devitrification( becoming opaque and Fluoride glass is prone to devitrification( becoming opaque and crystalline). crystalline).

Fiber making techniques have to take this into account to Fiber making techniques have to take this into account to avoid the formation of micro crystalloids, which have a drastic avoid the formation of micro crystalloids, which have a drastic effect on scattering losses. effect on scattering losses.

Although these glasses potentially offer intrinsic Although these glasses potentially offer intrinsic minimum losses of 0.01 to 0.001 dB/Km, minimum losses of 0.01 to 0.001 dB/Km, fabricating long lengths of these fibers is difficult fabricating long lengths of these fibers is difficult becausebecause

Active Glass FibersActive Glass Fibers

Incorporating rare earth elements (atomic numbers 57 to 71) into a Incorporating rare earth elements (atomic numbers 57 to 71) into a glass give the resulting material new optical and magnetic properties. glass give the resulting material new optical and magnetic properties. These new properties allow the material to perform amplification, These new properties allow the material to perform amplification, attenuation, and phase retardation on the light passing through it. attenuation, and phase retardation on the light passing through it. Doping can be done both for silica and halide glasses.Doping can be done both for silica and halide glasses.

Two commonly used materials for fiber lasers are erbium and Two commonly used materials for fiber lasers are erbium and neodymium. The ionic concentrations of the rare earth elements are neodymium. The ionic concentrations of the rare earth elements are low to avoid clustering affects. low to avoid clustering affects.

By, examining the absorption and fluorescence spectra of these By, examining the absorption and fluorescence spectra of these materials, one can use an optical source which emits at an absorption materials, one can use an optical source which emits at an absorption wavelength to excite electrons to higher energy levels in the rare earth wavelength to excite electrons to higher energy levels in the rare earth dopants. When these excited electrons drop to lower energy levels, dopants. When these excited electrons drop to lower energy levels, they emit light in a narrow optical spectrum at the fluorescence they emit light in a narrow optical spectrum at the fluorescence wavelength.wavelength.

Plastic Clad Glass Plastic Clad Glass FibersFibers

Optical fibers constructed with glass cores and glass claddings are very Optical fibers constructed with glass cores and glass claddings are very important for long distance applications where the very low losses important for long distance applications where the very low losses achievable in these fibers are needed. achievable in these fibers are needed.

For short distance applications (upto several 100 m), where higher For short distance applications (upto several 100 m), where higher losses are tolerable, the less expensive plastic clad silica fibers can be losses are tolerable, the less expensive plastic clad silica fibers can be used. used.

These fibers are composed of silica cores with the lower refractive These fibers are composed of silica cores with the lower refractive index cladding being a polymer (plastic material). These fibers are index cladding being a polymer (plastic material). These fibers are often referred to as PCS (Plastic Clad Silica Fibers).often referred to as PCS (Plastic Clad Silica Fibers).

A common material source for the silica core is selected high purity A common material source for the silica core is selected high purity natural quartz. A common cladding material is a silicone raisin having a natural quartz. A common cladding material is a silicone raisin having a refractive index of 1.405 at 850 nm. refractive index of 1.405 at 850 nm.

Silicon raisin is also frequently used as a protective coating for other Silicon raisin is also frequently used as a protective coating for other type of fibers. Another popular plastic cladding material is type of fibers. Another popular plastic cladding material is perfluoronated ethylene propylene (Teflon FEP). This low refractive perfluoronated ethylene propylene (Teflon FEP). This low refractive index, 1.338, of this material results in fibers with potentially large index, 1.338, of this material results in fibers with potentially large numerical apertures.numerical apertures.

Plastic claddings are only used for step index fibers. The core Plastic claddings are only used for step index fibers. The core diameters are larger (150 to 600 diameters are larger (150 to 600 μμm) than the standard 50 m) than the standard 50 μμm m diameter core of all glass graded index fibers, and the larger difference diameter core of all glass graded index fibers, and the larger difference in the core and cladding indices result in a high numerical aperture. in the core and cladding indices result in a high numerical aperture.

This allows low cost large area light sources to be used for coupling This allows low cost large area light sources to be used for coupling optical power into these fibers, thereby yielding comparatively optical power into these fibers, thereby yielding comparatively inexpensive but lower quality systems which are quite satisfactory for inexpensive but lower quality systems which are quite satisfactory for many applications.many applications.

PLASTIC FIBERSPLASTIC FIBERS

All plastic multimode step index fibers are good candidates for fairly All plastic multimode step index fibers are good candidates for fairly short (up to about 100 m) and low cost links.short (up to about 100 m) and low cost links.

Although they exhibit considerably greater signal attenuations than Although they exhibit considerably greater signal attenuations than glass fibers, the toughness and durability of plastic allow these fibers to glass fibers, the toughness and durability of plastic allow these fibers to be handled without special care. be handled without special care.

The high refractive index differences that can be achieved between the The high refractive index differences that can be achieved between the core and the cladding materials yield numerical apertures as high as core and the cladding materials yield numerical apertures as high as 0.6 and large acceptance angles of up to 700.6 and large acceptance angles of up to 7000. .

In addition, the mechanical flexibility of plastic allows these fibers to In addition, the mechanical flexibility of plastic allows these fibers to have large cores, but typical diameters ranging from 110 – 1400 have large cores, but typical diameters ranging from 110 – 1400 μμm. m.

These factors permit the use of inexpensive large area light These factors permit the use of inexpensive large area light emitting diodes which in conjunction the less expensive glass emitting diodes which in conjunction the less expensive glass fibers, make an economically attractive system. Examples of fibers, make an economically attractive system. Examples of plastic fiber constructions are:plastic fiber constructions are:

A polystyrene core (n1 = 1.6) and a methyl methacrylate A polystyrene core (n1 = 1.6) and a methyl methacrylate cladding (n2 = 1.49) to give an NA of 0.6.cladding (n2 = 1.49) to give an NA of 0.6.

A polymethyl methacrylate core (n1 = 1.49) and a cladding A polymethyl methacrylate core (n1 = 1.49) and a cladding made of its copolymer to give an NA of 0.5.made of its copolymer to give an NA of 0.5.

FIBER FABRICATIONFIBER FABRICATION

Two basic techniques are used in the Two basic techniques are used in the fabrication of all glass optical wave fabrication of all glass optical wave guides. These are the guides. These are the 

Direct Melt MethodsDirect Melt Methods    Vapour Phase Oxidation ProcessVapour Phase Oxidation Process

The direct melt methods follows traditional glass making procedures in The direct melt methods follows traditional glass making procedures in that optical fibers are made directly from the molten state of purified that optical fibers are made directly from the molten state of purified components of silicate glasses. components of silicate glasses.

In vapour phase oxidation process, highly pure vapours of metal halides In vapour phase oxidation process, highly pure vapours of metal halides (e.g., SiCl(e.g., SiCl44 and GeCl and GeCl44) react with oxygen to form a white powder of SiO) react with oxygen to form a white powder of SiO22 particles. particles.

The particles are then collected on the surface of a bulk glass by one of 4 The particles are then collected on the surface of a bulk glass by one of 4

different commonly used processes and are sintered (transformeddifferent commonly used processes and are sintered (transformed to a to a homogeneous glass mask by heating without melting) by one of a homogeneous glass mask by heating without melting) by one of a variety of techniques to form a clear glass rod or tube (depending on the variety of techniques to form a clear glass rod or tube (depending on the process). process).

This rod or tube is called a preform. It is typically around 10 to 25 mm in This rod or tube is called a preform. It is typically around 10 to 25 mm in diameter and 60 to 120 cm long. Fibers are made from perform by using diameter and 60 to 120 cm long. Fibers are made from perform by using the equipment shown in the figure 2.the equipment shown in the figure 2.

The perform is precision-fed into a circular heater called the drawing The perform is precision-fed into a circular heater called the drawing furnace. Here the preform end is softened to the point where it can be furnace. Here the preform end is softened to the point where it can be drawn into a very thin filament, which becomes the optical fiber. drawn into a very thin filament, which becomes the optical fiber.

The turning speed of the take up drum at the bottom of the draw tower The turning speed of the take up drum at the bottom of the draw tower determines how fast the fiber is drawn. This, in turn, will determine the determines how fast the fiber is drawn. This, in turn, will determine the thickness of the fiber, so that a precise rotation rate must be thickness of the fiber, so that a precise rotation rate must be maintained. maintained.

An optical fiber thickness monitor is used in a feedback loop for this An optical fiber thickness monitor is used in a feedback loop for this speed regulation. speed regulation.

To protect the bare glass fiber from external contaminants such as dust To protect the bare glass fiber from external contaminants such as dust and water vapour, an elastic coating is applied to the fiber immediately and water vapour, an elastic coating is applied to the fiber immediately after it is drawn.after it is drawn.

String materials

Collapse to preform

Fiber drawing

Vapour axial Deposition(VAD)

Utside vapour phaseOxidation process ( OVPO)

Modified chemical vapour Deposition (MCVD)

Plasma-activatedChemical vapourDeposition (PCVD)

Flame hydrolysis Chemical vapour deposition

Preform

Furnance

Fiber

TraversingHeat souece

Outside Vapour Outside Vapour Phase OxidationPhase Oxidation

   The first fiber to have a loss of less than 20 dB/Km was made at the Corning The first fiber to have a loss of less than 20 dB/Km was made at the Corning

Glass Works by the Glass Works by the Outside Vapour Phase Oxidation Outside Vapour Phase Oxidation (OVPO process). (OVPO process).

First, a layer of SiOFirst, a layer of SiO22 particles called a suite is deposited from a burner onto particles called a suite is deposited from a burner onto a rotating graphite or ceramic mandrel. The glass suite adheres to this bait a rotating graphite or ceramic mandrel. The glass suite adheres to this bait rod and, layer by layer rod and, layer by layer ≈≈200 layers , a cylindrical, porous glass perform is 200 layers , a cylindrical, porous glass perform is built up. built up.

Refractive index modification is achieved through the formation of dopants Refractive index modification is achieved through the formation of dopants from non-silica materials (TiOfrom non-silica materials (TiO22, GeO, GeO22, P, P22OO55, Al, Al22OO33 etc.). etc.).

By properly controlling the constituents of the metal halide vapour stream By properly controlling the constituents of the metal halide vapour stream during the deposition process, the glass compositions and dimensions during the deposition process, the glass compositions and dimensions desired for the core and cladding can be incorporated into the perform. desired for the core and cladding can be incorporated into the perform. Either step or graded index performs can thus be made.Either step or graded index performs can thus be made.

When the deposition process is completed, the mandrel is When the deposition process is completed, the mandrel is removed and the porous tube is then vitrified in a dry removed and the porous tube is then vitrified in a dry atmosphere at a high temperature (above 1400atmosphere at a high temperature (above 14000 0 C) to a clear C) to a clear glass preform.glass preform.

This clear perform is subsequently mounted in a fiber drawing This clear perform is subsequently mounted in a fiber drawing tower and made into a fiber. The central hole in the tube tower and made into a fiber. The central hole in the tube preform collapses during this drawing process. Several Km preform collapses during this drawing process. Several Km ≈≈ 10 10 Km of 120 Km of 120 μμm core diameter fiber have been produced. m core diameter fiber have been produced.

Bandwidth x Length = 3 GHz.Km can be produced. Losses Bandwidth x Length = 3 GHz.Km can be produced. Losses ≈≈1 1 dB/Km and 1.8 dB/Km at 1.2 and 1.55 dB/Km and 1.8 dB/Km at 1.2 and 1.55 μμm are possible.m are possible.

  Vapour Phase Axial Vapour Phase Axial

DepositionDeposition Another OVPO type process is the Another OVPO type process is the Vapour Phase Axial Deposition Vapour Phase Axial Deposition

method (VAD). method (VAD).

In this method the SiO2 particles are formed in the same way as the In this method the SiO2 particles are formed in the same way as the OVPO process. A porous preform is grown in the axial direction by OVPO process. A porous preform is grown in the axial direction by moving the rod upward. moving the rod upward.

The rod is also continuously rotated to maintain cylindrical symmetry of The rod is also continuously rotated to maintain cylindrical symmetry of the particle deposition.the particle deposition.

As the porous preform moves upward, it is transformed into a solid, As the porous preform moves upward, it is transformed into a solid, transparent rod preformed by zone melting (heating a narrow localized transparent rod preformed by zone melting (heating a narrow localized zone). zone).

The resultant preform can then be drawn into a fiber by heating it in The resultant preform can then be drawn into a fiber by heating it in another furnace.another furnace.

The preform has no central hole as occurs in the OVPO The preform has no central hole as occurs in the OVPO process.process.

The preform can be fabricated in continuous lengths which can The preform can be fabricated in continuous lengths which can effect process costs and product yields.effect process costs and product yields.

The fact that the deposition chamber and the process melting The fact that the deposition chamber and the process melting

ring heater are tightlyring heater are tightly connected to each other in the same connected to each other in the same enclosure allows the achievement of a clean environment.enclosure allows the achievement of a clean environment.

The fiber of length 100 Km can be drawn. Attenuation of 0.7 to The fiber of length 100 Km can be drawn. Attenuation of 0.7 to 2 dB/Km at a wavelength 1.181 2 dB/Km at a wavelength 1.181 μμm has been reported. m has been reported.

Both step and graded index fibers in either multimode or Both step and graded index fibers in either multimode or single mode varieties can be made by the VAD method. The single mode varieties can be made by the VAD method. The advantages of the VAD method are:advantages of the VAD method are:

Modified Chemical Modified Chemical Vapour DepositionVapour Deposition

The modified chemical vapour deposition (MCVD) process was The modified chemical vapour deposition (MCVD) process was pioneered at Bell labs and widely adopted elsewhere to pioneered at Bell labs and widely adopted elsewhere to produce very low loss graded index fibers.produce very low loss graded index fibers.

The glass vapour particles arising from the reaction of the The glass vapour particles arising from the reaction of the constituent metal halide gases and oxygen flow through the constituent metal halide gases and oxygen flow through the inside of a revolving silica tube. inside of a revolving silica tube.

As the silica particles are deposited, they are sintered to a As the silica particles are deposited, they are sintered to a clear glass layer by an oxy-hydrogen torch which travels back clear glass layer by an oxy-hydrogen torch which travels back and forth along the tube. and forth along the tube.

When the desired thickness of glass has been deposited, the When the desired thickness of glass has been deposited, the vapour flow is shut off and the tube is heated strongly to cause vapour flow is shut off and the tube is heated strongly to cause it to collapse into a solid rod preformed.it to collapse into a solid rod preformed.

The fiber that is subsequently drawn from this preformed rod The fiber that is subsequently drawn from this preformed rod will have a core that consists of the vapour deposited material will have a core that consists of the vapour deposited material and the cladding consisting of the original silica tube.and the cladding consisting of the original silica tube.

Loss: Approximately 0.2 dB/Km at wavelength 1.55 μm.Loss: Approximately 0.2 dB/Km at wavelength 1.55 μm.

Approximately 0.34 dB/Km for multimode fiber at wavelength Approximately 0.34 dB/Km for multimode fiber at wavelength 1.55 1.55 μμm.m.

Large scale batch production can give 30,000 Km of 50 Large scale batch production can give 30,000 Km of 50 μμm m core graded index fiber at wavelength 0.825 and 1.3 core graded index fiber at wavelength 0.825 and 1.3 μμm.m.

Normally 100 to 200 Km of fiber is produced.Normally 100 to 200 Km of fiber is produced.

Plasma Activated Chemical Plasma Activated Chemical

Vapour DepositionVapour Deposition Scientists at Philips Research invented the plasma activated chemical Scientists at Philips Research invented the plasma activated chemical

vapour deposition process (PCVD). The PCVD method is similar to the vapour deposition process (PCVD). The PCVD method is similar to the MCVD process in that deposition occurs within a silica tube.However, MCVD process in that deposition occurs within a silica tube.However, non-isothermal microwave plasma operating at low pressure initiates non-isothermal microwave plasma operating at low pressure initiates the chemical reaction. the chemical reaction.

With the silica tube held at temperatures in the range of 1,000 to 1,200With the silica tube held at temperatures in the range of 1,000 to 1,2000 0

C to reduce mechanical stresses in the growing glass films, a moving C to reduce mechanical stresses in the growing glass films, a moving microwave resonators operating at 2.45 GHz generates a plasma inside microwave resonators operating at 2.45 GHz generates a plasma inside the tube to activate the chemical reaction.the tube to activate the chemical reaction.

This process deposits clear glass material directly on the tube wall; This process deposits clear glass material directly on the tube wall; there is no soot formation. Thus, no sintering is required. When one has there is no soot formation. Thus, no sintering is required. When one has deposited the required glass thickness, the tube is collapsed into a deposited the required glass thickness, the tube is collapsed into a perform just as in the MCVD case. Over 200 Km of fiber can be perform just as in the MCVD case. Over 200 Km of fiber can be produced.produced.

Losses are: 0.3 dB/Km at 1.55 Losses are: 0.3 dB/Km at 1.55 μμm.m.

TYPES OF OPTICAL TYPES OF OPTICAL FIBERSFIBERS

It is necessary to consider the various optical fibers currently It is necessary to consider the various optical fibers currently available. available.

It is interesting to note, however, that although the high It is interesting to note, however, that although the high performance values quoted are for fibers produced and tested performance values quoted are for fibers produced and tested in the lab, the performance characteristics of commercially in the lab, the performance characteristics of commercially available fibers in many cases are now very close to these available fibers in many cases are now very close to these values indicating improvements made over recent years in the values indicating improvements made over recent years in the fiber materials preparation technologies.fiber materials preparation technologies.

In particular, high performance silica based fibers for operation In particular, high performance silica based fibers for operation in 3 major wavelength regions (0.8 to 0.9, 1.3 & 1.55 in 3 major wavelength regions (0.8 to 0.9, 1.3 & 1.55 μμm) are m) are now widely commercially available. now widely commercially available.

   Moreover, complex refractive index profile single mode fibers, Moreover, complex refractive index profile single mode fibers,

including dispersion modified fibers and polarization including dispersion modified fibers and polarization maintaining fibers are also commercially available and in the maintaining fibers are also commercially available and in the former case are starting to find system application within former case are starting to find system application within communications.communications.

Another relatively new area of commercial fiber development Another relatively new area of commercial fiber development is concerned with mid infrared range (2 to 5 is concerned with mid infrared range (2 to 5 μμm) often m) often employing heavy fluoride glass technology. However, the fiber employing heavy fluoride glass technology. However, the fiber products that exist for this region tend to be multimode with products that exist for this region tend to be multimode with relatively high losses and hence at present are only relatively high losses and hence at present are only appropriate for specialized applications.appropriate for specialized applications.

MMultimode Step ultimode Step Index FibersIndex Fibers

Multimode step index fibers may be fabricated from either multi-Multimode step index fibers may be fabricated from either multi-component glass compounds or doped silica. These fibers can have component glass compounds or doped silica. These fibers can have reasonably large core diameters and large NAs to facilitate efficient reasonably large core diameters and large NAs to facilitate efficient coupling to incoherent light sources such as LEDs. coupling to incoherent light sources such as LEDs.

The performance characteristics of this fiber type may vary The performance characteristics of this fiber type may vary considerably depending on the material used and the method of considerably depending on the material used and the method of preparation. preparation.

The doped silica fibers exhibit the best performance. Multi-The doped silica fibers exhibit the best performance. Multi-component glass and doped silica fibers are often referred to as component glass and doped silica fibers are often referred to as multi-component glass/glass (Glass clad glass) and silica/silica multi-component glass/glass (Glass clad glass) and silica/silica respectively. respectively.

Although the glass clad glass terminology is sometimes used Although the glass clad glass terminology is sometimes used vaguely to denote both types. vaguely to denote both types.

Typical structure for a glass Typical structure for a glass multimode step index fibermultimode step index fiber

Buffer jacketBuffer jacket

Primary coatingPrimary coatingn2n2

CladdingCladding n1 n1

CoreCore

  

  

  

  

Performance Performance CharacteristicsCharacteristics

ATTENUATION: ATTENUATION:

2.6 to 50 dB/Km at wavelength of 0.85 2.6 to 50 dB/Km at wavelength of 0.85 μμm, limited by m, limited by absorption or scattering. The wide variation in attenuation is absorption or scattering. The wide variation in attenuation is due to the large difference both within and between the two due to the large difference both within and between the two overall preparation methods (melting and deposition).overall preparation methods (melting and deposition).

BANDWIDTH APPLICATIONSBANDWIDTH APPLICATIONS::

6 to 50 MHz.Km. these fibers are best suited for short haul, 6 to 50 MHz.Km. these fibers are best suited for short haul, limited bandwidth and relatively low cost applications.limited bandwidth and relatively low cost applications.

Performance Performance CharacteristicsCharacteristics

ATTENUATION ATTENUATION :: 2.6 to 50 dB/Km at wavelength of 0.85 2.6 to 50 dB/Km at wavelength of 0.85 μμm, m, limited by absorption or scattering. limited by absorption or scattering.

The wide variation in attenuation is due to the large difference The wide variation in attenuation is due to the large difference both within and between the two overall preparation methods both within and between the two overall preparation methods (melting and deposition).(melting and deposition).

BANDWIDTH APPLICATIONSBANDWIDTH APPLICATIONS:: 6 to 50 MHz.Km. 6 to 50 MHz.Km.

These fibers are best suited for short haul, limited bandwidth These fibers are best suited for short haul, limited bandwidth and relatively low cost applications.and relatively low cost applications.

Multimode Graded Multimode Graded Index FibersIndex Fibers

These multimode fibers which have a graded index profile may also be These multimode fibers which have a graded index profile may also be fabricated using multi-component glasses or doped silica. However, fabricated using multi-component glasses or doped silica. However, they tend to be manufactured from materials with higher purities than they tend to be manufactured from materials with higher purities than the majority of multimode step index fibers in order to reduce fiber the majority of multimode step index fibers in order to reduce fiber losses. losses.

The performance characteristics of these fibers are therefore generally The performance characteristics of these fibers are therefore generally better than multimode step index fibers due to index grading and lower better than multimode step index fibers due to index grading and lower attenuation. attenuation.

These fibers tend to have smaller core diameters, although the overall These fibers tend to have smaller core diameters, although the overall diameter including the buffer jacket is usually about the same. diameter including the buffer jacket is usually about the same.

Typical structure for a glass Typical structure for a glass multimode graded index fibermultimode graded index fiber

Buffer jacketBuffer jacketPrimary CoatingPrimary Coating

n2n2CladdingCladdingCoreCore

Refractive IndexRefractive Index n1 n1

StructureStructure  Core diameter: Core diameter: 30 to 100 30 to 100 μμm.m.Cladding diameter: Cladding diameter: 100 to 150 100 to 150 μμm.m.Buffer Jacket diameter: Buffer Jacket diameter: 250 to 1,000 250 to 1,000 μμmmNumerical Aperture: Numerical Aperture: 0.2 to 0.30.2 to 0.3  

Although the above general parameters encompass most of the Although the above general parameters encompass most of the commonly available multimode graded index fibers, in commonly available multimode graded index fibers, in particular the following major groups have now emerged:particular the following major groups have now emerged:

50 50 μμm/125 m/125 μμm (core/cladding) diameter fibers with typical NA between m (core/cladding) diameter fibers with typical NA between 0.2 & 0.24. These fibers were originally developed and standardized by 0.2 & 0.24. These fibers were originally developed and standardized by the CCITT for telecommunication applications at wavelengths of 0.85 the CCITT for telecommunication applications at wavelengths of 0.85 and 1.3 and 1.3 μμm. But now they are mainly utilized within data links and m. But now they are mainly utilized within data links and LANs.LANs.

62.5 62.5 μμm/125 m/125 μμm (core/cladding) diameter fibers with optical NA m (core/cladding) diameter fibers with optical NA between 0.26 and 0.29. Although these fibers were developed for between 0.26 and 0.29. Although these fibers were developed for longer distance, subscriber loop applications at operating wavelengths longer distance, subscriber loop applications at operating wavelengths of 0.85 and 1.3 of 0.85 and 1.3 μμm, they are mainly used with LANs.m, they are mainly used with LANs.

85 85 μμm/125 m/125 μμm (core cladding) diameter fibers with typical NA 0.26 and m (core cladding) diameter fibers with typical NA 0.26 and 0.30. These fibers were developed for operation at wavelengths of 0.85 0.30. These fibers were developed for operation at wavelengths of 0.85 and 1.3 and 1.3 μμm in low cost, short distance applications. m in low cost, short distance applications.

They can, however, be utilized at the 1.3 They can, however, be utilized at the 1.3 μμm operating m operating wavelength and have. Therefore. Also found application within wavelength and have. Therefore. Also found application within LANs.LANs.

100 100 μμm/125 m/125 μμm (core/cladding) diameter fibers with NA of 0.29. m (core/cladding) diameter fibers with NA of 0.29. These fibers were developed to provide high coupling efficiency These fibers were developed to provide high coupling efficiency to LEDs at a wavelength of 0.85 to LEDs at a wavelength of 0.85 μμm in low cost, short distance m in low cost, short distance applications. applications.

They can, however, be utilized at the 1.3 They can, however, be utilized at the 1.3 μμm operating m operating wavelength and have, therefore, also found application within wavelength and have, therefore, also found application within LANs.LANs.

Performance Performance CharacteristicsCharacteristics

   ATTENUATION: 2 to 10 dB/Km at a wavelength of 0.85 ATTENUATION: 2 to 10 dB/Km at a wavelength of 0.85 μμm with m with

generally a scattering limit. Average losses of around 0.4 and generally a scattering limit. Average losses of around 0.4 and 0.25 dB/Km can be obtained a wavelengths of 1.3 and 1.55 0.25 dB/Km can be obtained a wavelengths of 1.3 and 1.55 μμm m respectively.respectively.

BANDWIDTH APLICATIONSBANDWIDTH APLICATIONS:: 300 MHz.Km to 300 GHz.Km. 300 MHz.Km to 300 GHz.Km.

These fibers are best suited for medium haul, medium to high These fibers are best suited for medium haul, medium to high bandwidth applications using incoherent and coherent bandwidth applications using incoherent and coherent multimode sources (i.e., LEDs and injection lasers multimode sources (i.e., LEDs and injection lasers respectively).respectively).

  Single Mode FibersSingle Mode Fibers

Single mode fibers can have either a step index or graded index profile. The benefits of Single mode fibers can have either a step index or graded index profile. The benefits of using graded index profile are to provide dispersion modified single mode fibers. using graded index profile are to provide dispersion modified single mode fibers.

The more sophisticated single mode fiber structures used to produce polarization The more sophisticated single mode fiber structures used to produce polarization maintaining fibers make these fibers quite expensive at present and thus they are not maintaining fibers make these fibers quite expensive at present and thus they are not generally utilized within optical fiber communication systems. Therefore, at present, generally utilized within optical fiber communication systems. Therefore, at present, commercially available single mode fibers are still usually step index.commercially available single mode fibers are still usually step index.

They are high quality fibers for wideband, long haul transmission and are generally They are high quality fibers for wideband, long haul transmission and are generally fabricated from doped silica (silica clad silica) in order to reduce attenuation.fabricated from doped silica (silica clad silica) in order to reduce attenuation.

Although single mode fibers have small core diameters to allow single mode Although single mode fibers have small core diameters to allow single mode propagation, the cladding diameter must be at least 10 times the core diameter to avoid propagation, the cladding diameter must be at least 10 times the core diameter to avoid losses from evanescent field. losses from evanescent field.

Hence with a buffer jacket to provide protection and strength, single mode fibers have Hence with a buffer jacket to provide protection and strength, single mode fibers have similar overall diameters to multimode fibers. similar overall diameters to multimode fibers.

Typical structure for a silica single mode step Typical structure for a silica single mode step index fiberindex fiber

Buffer jacketBuffer jacket

Primary claddingPrimary cladding

CladdingCladding

CoreCore

StructureStructure

  Core diameter: 5 to 10 Core diameter: 5 to 10 μμm, typical around 8.5 m, typical around 8.5 μμmm

Cladding diameter: generally 125 Cladding diameter: generally 125 μμmm

Buffer Jacket diameter: 250 to 1,000 Buffer Jacket diameter: 250 to 1,000 μμmm

Numerical Aperture: 0.08 to 0.15, usually around 0.10Numerical Aperture: 0.08 to 0.15, usually around 0.10

Performance Performance CharacteristicsCharacteristics

   ATTENUATION: 2 to 5 dB/Km with a scattering limit of around 1 ATTENUATION: 2 to 5 dB/Km with a scattering limit of around 1

dB/Km at a wavelength of 0.85 dB/Km at a wavelength of 0.85 μμm. In addition, average losses of m. In addition, average losses of 0.35 and 0.21 dB/Km at wavelengths of 1.3 and 1.55 0.35 and 0.21 dB/Km at wavelengths of 1.3 and 1.55 μμm can be m can be obtained in a manufacturing environment.obtained in a manufacturing environment.

BANDWIDTH: Greater than 500 MHz.Km.BANDWIDTH: Greater than 500 MHz.Km. In theory, the bandwidth is limited by waveguide and material In theory, the bandwidth is limited by waveguide and material

dispersion to approximately 40 GHz.Km at a wavelength of 0.85 dispersion to approximately 40 GHz.Km at a wavelength of 0.85 μμm. m.

However, practical bandwidths in excess of 10 GHz.Km are obtained However, practical bandwidths in excess of 10 GHz.Km are obtained at a wavelength of 1.3 at a wavelength of 1.3 μμm.m.

APPLICATIONS: These fibers are ideally suited for high bandwidth, APPLICATIONS: These fibers are ideally suited for high bandwidth, very long haul applications using single mode injection laser very long haul applications using single mode injection laser sources.sources.

Plastic Clad FibersPlastic Clad Fibers Plastic clad fibers are multimode and have either a step index or a Plastic clad fibers are multimode and have either a step index or a

graded index profile.graded index profile.

They have a plastic cladding (often a silicone rubber) and a glass They have a plastic cladding (often a silicone rubber) and a glass core which is frequently silica (i.e., plastic and silica PCS fibers). core which is frequently silica (i.e., plastic and silica PCS fibers).

The PCS fibers exhibit lower radiation-induced losses than silica The PCS fibers exhibit lower radiation-induced losses than silica clad silica fibers and, therefore, have an improved performance in clad silica fibers and, therefore, have an improved performance in certain environments.certain environments.

Plastic clad fibers are generally slightly cheaper than the Plastic clad fibers are generally slightly cheaper than the corresponding glass fibers, but usually have more limited corresponding glass fibers, but usually have more limited performance characteristics. performance characteristics.

Typical structure for a plastic clad silica Typical structure for a plastic clad silica multimode step index fibermultimode step index fiber

Buffer JacketBuffer Jacket

Cladding (Plastic)Cladding (Plastic)

CoreCore n1 n1

StructureStructureand and Performance CharacteristicsPerformance Characteristics

StructureStructure  Core diameter: Core diameter: Step Index: Step Index: 100 to 500 100 to 500 μμmm

Graded Index:Graded Index: 50 to 100 50 to 100 μμmmCladding diameter: Cladding diameter: Step Index: Step Index: 300 to 800 300 to 800 μμmm

Graded Index: Graded Index: 125 to 150 125 to 150 μμmmBuffer Jacket diameter: Buffer Jacket diameter: Step Index: Step Index: 500 to 1,000 500 to 1,000 μμmm

Graded Index: Graded Index: 250 to 1,000 250 to 1,000 μμmmNumerical Aperture: Numerical Aperture: Step Index: Step Index: 0.2 to 0.50.2 to 0.5

Graded Index: Graded Index: 0.2 to 0.30.2 to 0.3

  Performance CharacteristicsPerformance Characteristics  ATTENUATION:ATTENUATION: Step Index: Step Index: 5 to 50 dB/Km5 to 50 dB/Km

Graded Index: Graded Index: 4 to 15 dB/Km4 to 15 dB/Km  

All Plastic FibersAll Plastic Fibers

All plastic fibers or polymeric fibers are exclusively of the multimode All plastic fibers or polymeric fibers are exclusively of the multimode step index type with large core and cladding diameters. Hence there is step index type with large core and cladding diameters. Hence there is a reduced requirement for a buffer jacket for fiber protection and a reduced requirement for a buffer jacket for fiber protection and strengthening. strengthening.

These fibers are usually cheaper to produce and easier to handle than These fibers are usually cheaper to produce and easier to handle than the corresponding silica based glass variety. However, their the corresponding silica based glass variety. However, their performance (especially for optical transmission in the infrared) is performance (especially for optical transmission in the infrared) is restricted, giving them limited use in communication applications.restricted, giving them limited use in communication applications.

All plastic fibers, however, generally have large NA, which allow easier All plastic fibers, however, generally have large NA, which allow easier coupling of light into the fiber from a multimode source. coupling of light into the fiber from a multimode source. 

  

Early plastic fibers fabricated with a polymethyl methacrylate Early plastic fibers fabricated with a polymethyl methacrylate (PMMA) and a fluorinated acrylic cladding exhibited losses (PMMA) and a fluorinated acrylic cladding exhibited losses around 500 dB/Km. around 500 dB/Km.

Subsequently, a continuous casting process was developed for Subsequently, a continuous casting process was developed for PMMA and losses as low as 110 dB/Km were achieved in the PMMA and losses as low as 110 dB/Km were achieved in the visible wavelength region the loss mechanisms in PMMA and visible wavelength region the loss mechanisms in PMMA and polystyrene core fibers are similar to those in glass fibers.polystyrene core fibers are similar to those in glass fibers.

Typical structure for an all plastic Typical structure for an all plastic fiberfiber

Cladding

Core

Structure and Performance Structure and Performance CharacteristicsCharacteristics

StructureStructure

Core diameter: Core diameter: 200 to 600 200 to 600 μμmmCladding diameter: Cladding diameter: 450 to 1,000 450 to 1,000 μμmmNumerical Aperture: Numerical Aperture: 0.5 to 0.60.5 to 0.6

  

Performance CharacteristicsPerformance Characteristics   ATTENUATION: 50 to 1,000 dB/Km at a wavelength of 0.65 ATTENUATION: 50 to 1,000 dB/Km at a wavelength of 0.65 μμmm

BANDWIDTH: This is not usually specified as transmission is generally BANDWIDTH: This is not usually specified as transmission is generally limited to only tens of meters.limited to only tens of meters.

APPLICATIONS: these fibers can only be used for very short haul (i.e. in APPLICATIONS: these fibers can only be used for very short haul (i.e. in house) low cost links. However, fiber coupling and termination are house) low cost links. However, fiber coupling and termination are relatively easy and do not require sophisticated techniques.relatively easy and do not require sophisticated techniques.

Many Optical Fibers In The Many Optical Fibers In The Market Market

There are several types of fibers based both on the transmission modes and There are several types of fibers based both on the transmission modes and the refractive index profile. It is important to know that the design of an the refractive index profile. It is important to know that the design of an optical fiber depends on the needs it is supposed to meet.optical fiber depends on the needs it is supposed to meet.

Key parameters like Key parameters like attenuationattenuation, , bandwidthbandwidth, , dispersiondispersion, and , and tensile strengthtensile strength are the most considered.are the most considered.

Also the protection of the fiber from external factors like humidity, heat, Also the protection of the fiber from external factors like humidity, heat, cold, and water is contemplated. That's why plastic sheaths where the fiber cold, and water is contemplated. That's why plastic sheaths where the fiber is enclosed in, are used. The whole material comprising the single fiber or is enclosed in, are used. The whole material comprising the single fiber or bundle of fibers, the sheaths, and the jacket, is usually referred as a bundle of fibers, the sheaths, and the jacket, is usually referred as a fiber fiber cablecable..

Obviously these cables also must satisfy requirements such as high Obviously these cables also must satisfy requirements such as high flexibility, resistance to kinks and crushing, and light weight.flexibility, resistance to kinks and crushing, and light weight.

OPTICAL FIBER CABLESOPTICAL FIBER CABLES They can be safely installed and maintained in all the environments (e.g. They can be safely installed and maintained in all the environments (e.g.

underground ducts) in which metallic conductors are normally placed. underground ducts) in which metallic conductors are normally placed. Therefore, when optical fibers are to be installed in a working environment, Therefore, when optical fibers are to be installed in a working environment, their mechanical properties are of prime importance.their mechanical properties are of prime importance.

In this respect, the unprotected optical fiber has several disadvantages with In this respect, the unprotected optical fiber has several disadvantages with regard to its strength and durability. Bare glass fibers are brittle and have regard to its strength and durability. Bare glass fibers are brittle and have small cross sectional areas which make them very susceptible to damage when small cross sectional areas which make them very susceptible to damage when employing normal transmission line handling procedures.employing normal transmission line handling procedures.

It is, therefore, necessary to cover the fibers to improve their tensile strength It is, therefore, necessary to cover the fibers to improve their tensile strength and to protect them against external influences. This is usually achieved by and to protect them against external influences. This is usually achieved by surrounding the fiber with a series of protective layers, which is referred to as surrounding the fiber with a series of protective layers, which is referred to as coating and cabling. coating and cabling.

The initial coating of plastic with high elastic modulus is applied directly to the The initial coating of plastic with high elastic modulus is applied directly to the fiber cladding. It is then necessary to incorporate the coated and buffered fiber fiber cladding. It is then necessary to incorporate the coated and buffered fiber into an optical cable to increase its resistance to mechanical strain and stress into an optical cable to increase its resistance to mechanical strain and stress as well as adverse environmental conditions.as well as adverse environmental conditions.

The functions of the optical cable may be summarized into four The functions of the optical cable may be summarized into four main areas. These aremain areas. These are

   Fiber Protection: Fiber Protection: The major function of the optical cable is to protect against The major function of the optical cable is to protect against

fiber damage and breakage both during installation and throughout the life of the fiber damage and breakage both during installation and throughout the life of the fiber.fiber.

Stability of the fiber transmission characteristics:Stability of the fiber transmission characteristics: the cabled fiber must have the cabled fiber must have good stable transmission characteristics which are comparable with the uncabled good stable transmission characteristics which are comparable with the uncabled fiber. Increases in optical attenuation due to cabling are quite usual and must be fiber. Increases in optical attenuation due to cabling are quite usual and must be minimized within the cable design.minimized within the cable design.

Cable strength: Cable strength: optical cables must have similar mechanical properties to optical cables must have similar mechanical properties to electric transmission cables in order that they may be handled in the same electric transmission cables in order that they may be handled in the same manner. These mechanical properties include tension, torsion, compression, manner. These mechanical properties include tension, torsion, compression, bending, squeezing and vibration. Hence the cable strength may be improved by bending, squeezing and vibration. Hence the cable strength may be improved by incorporating a suitable strength member and by giving the cable a properly incorporating a suitable strength member and by giving the cable a properly designed thick outer sheath.designed thick outer sheath.

   Identification and jointing of the fibers: This is specially Identification and jointing of the fibers: This is specially

important for cables including a large number of optical fibers. important for cables including a large number of optical fibers. If the fibers are arranged in a suitable geometry, it may be If the fibers are arranged in a suitable geometry, it may be possible to use multiple jointing techniques rather than jointing possible to use multiple jointing techniques rather than jointing each fiber individually.each fiber individually.

In order to consider the cabling requirements for fibers with In order to consider the cabling requirements for fibers with regard to (1) & (2), it is necessary to discuss the fiber strength regard to (1) & (2), it is necessary to discuss the fiber strength and durability as well as any possible sources of degradation of and durability as well as any possible sources of degradation of the fiber transmission characteristics, which are likely to occur the fiber transmission characteristics, which are likely to occur due to cabling.due to cabling.

CABLINGCABLING

The design of optical fiber cables must take account of the The design of optical fiber cables must take account of the constraints discussed in previous section. In particular, the cable constraints discussed in previous section. In particular, the cable must be designed so that the strain on the fiber in the cable does must be designed so that the strain on the fiber in the cable does not exceed 0.2%. not exceed 0.2%.

Alternatively, it is suggested that the permanent strain on the fiber Alternatively, it is suggested that the permanent strain on the fiber should be less than 0.1%. In practice, these constraints may be should be less than 0.1%. In practice, these constraints may be overcome in various ways, which are to some extent, dependent on overcome in various ways, which are to some extent, dependent on the cable’s application.the cable’s application.

Nevertheless, cable design may generally be separated into a Nevertheless, cable design may generally be separated into a number of major considerations. These can be summarized into number of major considerations. These can be summarized into the categories of fiber buffering, cable structural and strength the categories of fiber buffering, cable structural and strength members, and cable sheath and water barrier.members, and cable sheath and water barrier.

An approach commercialized by AT & T is the loose fiber bundle An approach commercialized by AT & T is the loose fiber bundle design . In this, cable up to 12 fibers are assembled into a bundle, design . In this, cable up to 12 fibers are assembled into a bundle, which is identified with a colour-coded binder. Several of the fiber which is identified with a colour-coded binder. Several of the fiber bundles are then placed inside a core tube. bundles are then placed inside a core tube.

This design does not employ a central strength member but relies This design does not employ a central strength member but relies upon an armored design using a reinforced sheath with a upon an armored design using a reinforced sheath with a polyethylene inner jacket.polyethylene inner jacket.

Moreover, the core construction provides for compact, low weight Moreover, the core construction provides for compact, low weight

cables with diameters of only 10 mm cables with diameters of only 10 mm 13 mm for fiber counts up to 13 mm for fiber counts up to 50 and 96 fibers respectively.50 and 96 fibers respectively.

An important application of fiber –optic light wave system is for An important application of fiber –optic light wave system is for telecommunication. Indeed, it is this application that started the telecommunication. Indeed, it is this application that started the optical fiber communications and has propelled it by demanding optical fiber communications and has propelled it by demanding higher and higher capacity light-wave systems.higher and higher capacity light-wave systems.

Terrestrial light-wave systems became available commercially Terrestrial light-wave systems became available commercially beginning in 1979. The first generation operated near 0.85 beginning in 1979. The first generation operated near 0.85 m and m and used multimode graded-index fiber as the transmission medium. used multimode graded-index fiber as the transmission medium.

A commercial light-wave system, operating at 90 M b/s with a A commercial light-wave system, operating at 90 M b/s with a repeater spacing about 12 km, realized a BL product of nearly 1 repeater spacing about 12 km, realized a BL product of nearly 1 (Gb/s)-km.(Gb/s)-km.

Telecommunication Fiber Telecommunication Fiber LinksLinks

The operating wavelength moved to 1.3 The operating wavelength moved to 1.3 m in second-generation m in second-generation lightwave systems to take advantage of low loss and low dispersion lightwave systems to take advantage of low loss and low dispersion near this wavelength.near this wavelength.

Many commercial systems operate near this wavelength. The BL Many commercial systems operate near this wavelength. The BL product of 1.3 product of 1.3 m lightwave systems is limited to about 100(Gb/s)-m lightwave systems is limited to about 100(Gb/s)-km when multimode semiconductor lasers are used inside the km when multimode semiconductor lasers are used inside the transmitter. transmitter.

A commercial 1.3m lightwave systems in 1987 provided data A commercial 1.3m lightwave systems in 1987 provided data transmission at 1.7 Gb/s with a repeater spacing of about 45 km. transmission at 1.7 Gb/s with a repeater spacing of about 45 km.

The third-generation light wave systems became available The third-generation light wave systems became available commercially in 1990. the operate near 1.5 m at bit rates I excess of 2 commercially in 1990. the operate near 1.5 m at bit rates I excess of 2 G b/s(typically at 2.88 Gb/s because of SONET specifications).G b/s(typically at 2.88 Gb/s because of SONET specifications).

Undersea transmission systems are used for innterconnection Undersea transmission systems are used for innterconnection communication.communication.

Reliability is of major concern for such systems , as repair are Reliability is of major concern for such systems , as repair are expensive. Generally, undersea systems are designed for a 25 years expensive. Generally, undersea systems are designed for a 25 years service life with most three failure during operation.service life with most three failure during operation.

The first fiber-optics undersea transmission system was installed in The first fiber-optics undersea transmission system was installed in 1988 in the Atlantic Ocean (TAT-98). It operates near 1.31988 in the Atlantic Ocean (TAT-98). It operates near 1.3m at a bit m at a bit rate of 295 Mb/s with repeater spacing of about 40 km.rate of 295 Mb/s with repeater spacing of about 40 km.

Several other transatlantic transmission system (TAT-9 to TAT-Several other transatlantic transmission system (TAT-9 to TAT-12) have been designed to meet the traffic demands. 12) have been designed to meet the traffic demands.

The TAT-9 system is designed to operate near 1.55 The TAT-9 system is designed to operate near 1.55 m ( a third m ( a third generation system) at a bit rate of 590 Mb/s with a repeater generation system) at a bit rate of 590 Mb/s with a repeater spacing of about 80 km; it would operate at a bit rate in excess of spacing of about 80 km; it would operate at a bit rate in excess of 1Gb/s and are expected to become operational by 1994. 1Gb/s and are expected to become operational by 1994.

The TAT-12 system is planned for 1995 and would operate at a bit The TAT-12 system is planned for 1995 and would operate at a bit rate of 2.4 Gb/s. Furthermore, it would make use of optical rate of 2.4 Gb/s. Furthermore, it would make use of optical amplifiers rather than electronic regenerators. amplifiers rather than electronic regenerators.

Similar lightwave systems are being planned for transmission across Similar lightwave systems are being planned for transmission across the Pacific ocean.the Pacific ocean.

The fourth and fifth generation of fiber-optic telecommunication The fourth and fifth generation of fiber-optic telecommunication systems are in the development stage. systems are in the development stage.

The fourth generation makes use of the coherent-detection techniques The fourth generation makes use of the coherent-detection techniques and is particularly suitable for transmission of multiple digital channels and is particularly suitable for transmission of multiple digital channels across the same fiber by using frequency division multiplexing.across the same fiber by using frequency division multiplexing.

The fifth generation makes use of the nonlinear effects in optical fibers The fifth generation makes use of the nonlinear effects in optical fibers and uses optical solutions for data transmission.and uses optical solutions for data transmission.

• LTK Cables offers simplex and duplex cable designs for voice, data, image and LTK Cables offers simplex and duplex cable designs for voice, data, image and videovideotransmission equipment interconnection. Construction are rugged,transmission equipment interconnection. Construction are rugged,flexible, easy handling, stripping and termination. They optimize for ease offlexible, easy handling, stripping and termination. They optimize for ease ofcable assemblies and utilize as jumper for intra-building distribution wiring cable assemblies and utilize as jumper for intra-building distribution wiring applications.applications.

                                                                                    

LTK Cables has developed up to 12 tight-buffered fibers, both light and heavy duties, distribution cables. Construction are designed for voice, data, image and video super-high-way-transmission.

Distribution cables contain several tight buffered fibers bundled under the same jacket, with aramid yarn reinforcement. These cables are small in size, and typically used in intra-building backbone cabling, horizontal cabling and computer room wiring that requires OFNR rating (UL1666).

                    

LTK Cables has developed both light and heavy duties BREAKOUT optical cables that are LTK Cables has developed both light and heavy duties BREAKOUT optical cables that are typically designed for voice, data, image and video super-high-way-transmission. BREAKOUT typically designed for voice, data, image and video super-high-way-transmission. BREAKOUT Cables are made of several simplex cables bundled together by SZ stranding, which provide Cables are made of several simplex cables bundled together by SZ stranding, which provide strong, rugged support and OFNR rated (UL1666) for riser applications.strong, rugged support and OFNR rated (UL1666) for riser applications.

Applications extend from intra-building backbone cabling, horizontal and computer room Applications extend from intra-building backbone cabling, horizontal and computer room wiring.wiring.

                                                                                    

Plastic Optical Fiber CablePlastic Optical Fiber Cable

PRODUCT DESCRIPTIONPRODUCT DESCRIPTION For short distance (5m) and low speed (6Mb/s) communication For short distance (5m) and low speed (6Mb/s) communication Immune to electromagnetic noise Immune to electromagnetic noise Links with 650nm plastic-packaged LED’s and silicon photodiodes Links with 650nm plastic-packaged LED’s and silicon photodiodes

for transmitter and receiver for transmitter and receiver Lower total system cost over glass fibers series Lower total system cost over glass fibers series

                                                                           

Plants of Optical FiberPlants of Optical Fiber

CeybaCeyba Core optical transmission systems. (Formerly known as Core optical transmission systems. (Formerly known as Solinet Systems) Solinet Systems)

CorningCorning Optical fiber, cable and photonic products Optical fiber, cable and photonic products

Crstal/Fiber Crstal/Fiber A/SA/S

Designs, manufactures and markets photonic crystal Designs, manufactures and markets photonic crystal fibers fibers

Cypress Cypress industriesindustries

Fiber optic and copper cables, connector products, and Fiber optic and copper cables, connector products, and custom manufacturing custom manufacturing

Plants of Optical Fiber Plants of Optical Fiber

SKOE,IncSKOE,Inc Fiber optic components, modules and Fiber optic components, modules and sub-systems sub-systems

SuncallSuncall Components for fiber optic networks Components for fiber optic networks

Samsung FiberopticSamsung Fiberoptic Optical solutions including optical fiber, Optical solutions including optical fiber, cables, and optical components cables, and optical components

S& L S& L TelekommunicationsTelekommunications

Fiber optic products Fiber optic products

Latest DiscoveriesLatest Discoveries

Optical Fibers Found in Deep-Sea SpongesOptical Fibers Found in Deep-Sea Sponges

MURRAY HILL, N.J., August 21 -- Scientists from Lucent Technologies' Bell MURRAY HILL, N.J., August 21 -- Scientists from Lucent Technologies' Bell Labs have found that a deep-sea sponge contains optical fiber that is remarkably Labs have found that a deep-sea sponge contains optical fiber that is remarkably similar to the optical fiber found in today's state-of-the-art telecommunications similar to the optical fiber found in today's state-of-the-art telecommunications networks. networks.

  The deep-sea sponge's glass fiber, designed through the course of evolution, may The deep-sea sponge's glass fiber, designed through the course of evolution, may possess certain technological advantages over industrial optical fiber, the possess certain technological advantages over industrial optical fiber, the scientists report in today's issue of the journal Nature. scientists report in today's issue of the journal Nature.

"We believe this novel biological opticl fiber may shed light on new bio-inspired "We believe this novel biological opticl fiber may shed light on new bio-inspired processes that may lead to better fiber optic materials and networks," said Joanna processes that may lead to better fiber optic materials and networks," said Joanna Aizenberg, the Bell Labs materials scientist who led the research team. "Mother Aizenberg, the Bell Labs materials scientist who led the research team. "Mother Nature's ability to perfect materials is amazing, and the more we study biological Nature's ability to perfect materials is amazing, and the more we study biological organisms, the more we realize how much we can learn from them." organisms, the more we realize how much we can learn from them."

The discovery of marine The discovery of marine optical fiber is the latest optical fiber is the latest Bell Labs contribution in Bell Labs contribution in the emerging field of the emerging field of science known as science known as biomimetics, which takes biomimetics, which takes engineering principles from engineering principles from the natural world and the natural world and applies them to manmade applies them to manmade materials and technologies. materials and technologies.

Holey Fiber Supports Holey Fiber Supports Megawatt PulsesMegawatt Pulses

Scientists at Corning Inc. in Corning, N.Y., have developed a hollow-Scientists at Corning Inc. in Corning, N.Y., have developed a hollow-core photonic bandgap fiber that supports ultrashort pulses of infrared core photonic bandgap fiber that supports ultrashort pulses of infrared radiation with peak powers more than 100 times greater than those radiation with peak powers more than 100 times greater than those tolerated by conventional optical fiber. Such fibers promise applications tolerated by conventional optical fiber. Such fibers promise applications across a variety of fields, including telecommunications. across a variety of fields, including telecommunications.

  The researchers produced the fiber by the stack-and-draw method, The researchers produced the fiber by the stack-and-draw method, bundling capillaries to create a preform that they draw into a fiber while bundling capillaries to create a preform that they draw into a fiber while monitoring the exterior diameter of the pulled product. monitoring the exterior diameter of the pulled product.

The fiber in cross section features a 12.7-µm-diameter central hole The fiber in cross section features a 12.7-µm-diameter central hole surrounded by eight rings of hexagonal airholes with a pitch of 4.7 µm, a surrounded by eight rings of hexagonal airholes with a pitch of 4.7 µm, a structure that offers a transmission window from 1395 to 1510 nm and structure that offers a transmission window from 1395 to 1510 nm and an attenuation of 13 dB/km at 1500 nm.an attenuation of 13 dB/km at 1500 nm.

Origin of 'Fiber Fuse' Is Origin of 'Fiber Fuse' Is RevealedRevealed

In the argot of fiber optics engineers, a "fiber fuse" In the argot of fiber optics engineers, a "fiber fuse" occurs when a fiber, overloaded with optical power, fails occurs when a fiber, overloaded with optical power, fails catastrophically.catastrophically.

  In a fiber fuse, a brilliant, highly visible intrafiber burn In a fiber fuse, a brilliant, highly visible intrafiber burn propagates backward from the original damage site propagates backward from the original damage site toward the optical source at speeds that can reach several toward the optical source at speeds that can reach several meters per second. meters per second.

Measurement of the burn's color temperature indicates Measurement of the burn's color temperature indicates that the fiber core reaches temperatures as high as 5400 that the fiber core reaches temperatures as high as 5400 K, sufficient to vaporize the glass. K, sufficient to vaporize the glass.

OFS multimode fiber coating gives lower OFS multimode fiber coating gives lower attenuationattenuation

Enhanced coating reduces attenuation, enables outstanding Enhanced coating reduces attenuation, enables outstanding performance at extreme temperaturesperformance at extreme temperatures

52nd IWCS / Focus - PHILADELPHIA, Nov. 19, 2003- OFS, 52nd IWCS / Focus - PHILADELPHIA, Nov. 19, 2003- OFS, designer, manufacturer, and supplier of leading edge fiber optic designer, manufacturer, and supplier of leading edge fiber optic products, today introduced Flex-10products, today introduced Flex-10TMTM coating, an enhanced coating, an enhanced multimode fiber coating that results in lower attenuation, especially multimode fiber coating that results in lower attenuation, especially in tight-buffer cable; improved cable performance in extreme in tight-buffer cable; improved cable performance in extreme temperature environments; and excellent mechanical stripping. temperature environments; and excellent mechanical stripping.

Flex-10 coating will be used with all OFS multimode products, Flex-10 coating will be used with all OFS multimode products, including the company's line of LaserWaveincluding the company's line of LaserWaveTMTM fibers designed for 1 fibers designed for 1 Gb/s and 10 Gb/s premises networks, as well as OFS laser-optimized Gb/s and 10 Gb/s premises networks, as well as OFS laser-optimized 62.5um fibers.62.5um fibers.

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