Irfan khan OPTICAL FIBERS: STRUCTURES, WAVEGUIDING, AND FABRICATION

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OPTICAL FIBERS: STRUCTURES, WAVEGUIDING,

AND FABRICATION

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The Nature of Light1. Light is a transverse, electromagnetic wave that can be seen by

humans.

2. The wave nature of light was first illustrated through experiments on

diffraction and interference.

3. Like all electromagnetic waves, light can travel through a vacuum.

4. The transverse nature of light can be demonstrated through

polarization.

5. The speed of light depends upon the medium through which it travels.

6. Intensity is the absolute measure of a light wave's power density

7. Brightness is the relative intensity as perceived by the average human

eye.

8. The frequency of a light wave is related to its energy and color.

9. The wavelength of a light wave is inversely proportional to its

frequency.

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irfan

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Spherical and plane wave fronts

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Field distributions in plane E&M waves

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The Structure of an Electromagnetic Wave. Electric and magnetic fields areactually superimposed over the top of one another but are illustrated separately for clarity in illustration. The z-direction can be considered to be either a representation in space or the passing of time at a single point.

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Amplitude Fluctuation in an Electromagnetic Wave. Here both the electric fieldand the magnetic field are shown as a single field oscillating about a locus of points which forms the line of travel.

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Basic Optical Laws and DefinitionsRefractive Index

The ratio of the speed of light in a vacuum to that in

matter is known as the refractive index or index of

refraction n of the material and is given by

Typical values of n are1.00 for air, 1.33 for water, 1.45 for silica glass2.42 for diamond.

larger value of n = Denser materiallower value of n = Less denser material

n = c / v

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Index of Refractionn1<n2<n3

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Reflection of light• Some part of the light reflected when strikes

on a surface• Laws of reflection of light

– Angle of incident is equal to angle of reflection– The incident ray, the normal and the reflected ray

all lies in same direction

Refraction of light• When light enters from one medium to other

medium– Direction and velocity are changed– It is called refraction of light

Refraction and reflection

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– When light passes from rare to dense medium, it bends towards the normal

– When light passes from dense to rare medium, it bends away from the normal

– Law of refraction is• The incident ray, the normal, and the

refracted ray at the point of incident all lies in the same plane

• The ratio of the sine of angle incidence to the sine of angle of refraction is always constant

– This ratio is called refractive index


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Diagrams illustrating reflection and refraction of light, viewed as waves and particles.

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• Snell,s Law– Snell discovered the relationship between

the refractive indices of the materials and the sine of the angles as:• n1 sinф1 = n2 sinф2

– If the angle of refraction is 90 then it is equal to 1 so

• Sinфc =n2 / n1


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• Total internal reflection– When light passes from denser medium

to rarer medium it bends away from the normal

– The incident angle for which angle of refraction is 90° is called critical angle

– If incident angle becomes more than critical angle all the light will reflect back to the same denser medium

– Such a phenomenon is called total internal reflection


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Angle of Refraction

Angle of ReflectionAngle of Incidence =

D

The critical angle of incidence.

GlassAir

B

GlassAir

Angle of IncidenceA

GlassAir

Critical Angle

90 0C

GlassAir

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Polarization Components of Light

•Light is composed of one or more transverse electromagnetic waves

•Electric field (called an E field) and a magnetic field (called an H field) component.

•In a transverse wave the directions of the vibrating electric and magnetic fields are perpendicular to each other and are at right angles to the direction of propagation of the wave

•Vibrations in the electric field are parallel to one another at all points in the wave, so that the electric field forms a plane called the plane of vibration

•All points in the magnetic field component of the wave lie in a plane that is at right angles to the electric field plane.

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Unpolarized light

An ordinary light wave is made up of many transverse waves that vibrate in a variety of directions (i.e., in more than one plane) and is referred to as unpolarized light.

Any arbitrary direction of vibration can be represented as a combination of a parallel vibration and a perpendicular vibration

As soon as light interacts with anything, whether through reflection, transmission, or scattering, there is opportunity for polarization to be induced.

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The refracted light is polarized depends on the angle at which the light approaches the surface and on the material itself.

Unpolarized light can be split into separate polarization components either by reflection off a nonmetallic surface or by refraction when the light passes from one material to another.

In the case when all the electric field planes of the different transverse waves are aligned parallel to one another, then the light wave is linearly polarized. This is the simplest type of polarization.

Unpolarized light

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Polarized/unpolarized waves on rope.

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Multitude of polarization components

Parallel polarization components

Perpendicular polarization components

Polarization represented as a combination of a parallel vibration and perpendicular vibration

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Ф1 Ф2

n2 < n1

n1

Material interface

Incident rayReflected ray

Refracted ray

Perpendicular polarization

Parallel polarization

Partially refracted perpendicular polarization

Behavior of an unpolarized light beam at the interface between air and a nonmetallic surface

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Depending on the orientation of the slot, the train of waves (a) goes entirely through the slot; (b) is partly reflected and partly transmitted with changed angles of rope vibration; or (c) is completely reflected.

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Polarization-Sensitive Materials

1. Polarizer

2. Faraday rotator

3. Birefringent crystals

A polarizer is a material or device that transmits only one polarization component and blocks the other.

A Faraday rotator is a device that rotates the state of polarization (SOP) of light passing through it by a specific amount

Certain crystalline materials have a property called double refraction or birefringence. This means that the indices of refraction are slightly different along two perpendicular axes of the crystal. A device made from such materials is known as a spatial walk-off polarizer (SWP).

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Polarizer

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A Faraday rotator is a device that rotates the state of polarization clockwise by 45o or a quarter of a wavelength

Faraday rotator

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Faraday rotator

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Faraday rotator

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Birefringent crystals

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Some Common Birefringent Crystals and Their Ordinary and Extraordinary Indices of Refraction

Birefringent crystals

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Intentionally Left Blank

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Optical fiber modes and configurations

Fiber Structures

Cross sections of a generic fiber structure showing a core, a cladding, and a buffer coating

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Single fiber structure

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Core

1. Light propagates along the core of the fiber.

2. Core material is highly pure silica SiO2 and is surrounded by glass cladding.

Cladding

1. Cladding reduces scattering loss that results from the dielectric discontinuities at the core surface.

2. It adds mechanical strength to the fiber

3. It protects the core from absorbing surface contaminants with which it could come in contact.

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• What does a Micron look like?

Human Hair

.0035 inch

90 Micron

9 Microns

1 Micron

.000039 inch

.001 mm

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• Modes– Simply can be defined as the different paths of the light through

the optical fiber cable– Every mode is represented by a unique solution of the Maxwell’s

equation inside the core– The stable Field distribution along the x-axis with only a periodic

z-dependence is known as mode

Fiber Types

Generally two types

1. Single mode

2. Multimode

Step index Fiber

Graded index Fiber

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Fiber Types

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– Only permits the fundamental mode of the

light

• Smaller diameter of the core

• Numerical aperture is also small

• Reduced acceptance angle

• Difficult to couple the light in the fiber

Single mode fiber

Fiber Types

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– Transmits a large number of modes

– Each mode has the different path through the fiber

– Each mode arrives at the end at slightly different time

(modal dispersion)

– Modal dispersion can be reduced by varying the

refractive index with in the core

– There are two types of multimode fibers

• Step index and graded index

Fiber Types

Multimode fiber

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• Step index Multimode fiber– The core of the fiber has the uniform refractive

index.

• Graded index Multimode Fiber

Graded-index fiber becoming very popular for specialized applications.

It is relatively expensive to manufacture, due to its complex core structure.

Fiber Types

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Fiber Types

Advantages Multimode Fiber:

1. Easier to launch optical power into the fiber.

2. Easier to connect similar optical fibers.

3. LED are used for launching optical power whereas single mode fiber use Laser.

• LEDs are easier to make

• Less expensive

• Less complex circuitry

• Longer life time

Disadvantage:

1. Intermodal dispersion

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Ray optics representation of the propagation mechanism in an ideal step index fiber.

Ray Optics

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• Acceptance angle– The entering rays which have the angle

greater than θc can be transmitted in optical fiber

– As the fiber is Circular, so angle is applicable in two dimensions and would look like a cone

– The range of incident angles which can be used for total Internal Reflection is called Cone of acceptance

–

Ray Optics

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• Numerical Aperture

It is measure of fiber’s light gathering ability.

This represent the coupling of light into the fiber core.

Think of the aperture as a funnel, the larger the funnel the more usable light that’s pumped into the core.

Ray Optics

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• Numerical Aperture

Light will be accepted and propagated only if it enters the core and strikes the cladding at an angle greater than the critical angle.

Any light rays striking the core within this acceptance cone will be propagated down the fiber.

Sin value of acceptance angle is called Numerical aperture.

Ray Optics

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Ray Optics

Critical angle

Sin θc = n2 / n1

Maximum entrance angle

n sin θ0,max =n1 sin θc = (n12 - n22 ) 1/2

Numerical Aperture NA

NA= n sin θ0,max = (n12 - n2

2 ) 1/2

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Optical rays transmission through dielectric slab waveguide

ccnn 2

;21

sin

cos

2

sintan

1

22

2211

n

nnmdn

For TE-case, when electric waves are normal to the plane of incidence must be satisfied with following relationship:

[2-25]

Optical Fiber communications, 3rd ed.,G.Keiser,McGrawHill, 2000

O

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Note

• Home work 2-1) Find an expression for ,considering that the electric

field component of optical wave is parallel to the plane of incidence (TM-case).

• As you have seen, the polarization of light wave down the slab waveguide changes the condition of light transmission. Hence we should also consider the EM wave analysis of EM wave propagation through the dielectric slab waveguide. In the next slides, we will introduce the fundamental concepts of such a treatment, without going into mathematical detail. Basically we will show the result of solution to the Maxwell’s equations in different regions of slab waveguide & applying the boundary conditions for electric & magnetic fields at the surface of each slab. We will try to show the connection between EM wave and ray optics analyses.

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EM analysis of Slab waveguide• For each particular angle, in which light ray can be faithfully transmitted

along slab waveguide, we can obtain one possible propagating wave solution from a Maxwell’s equations or mode.

• The modes with electric field perpendicular to the plane of incidence (page) are called TE (Transverse Electric) and numbered as:

Electric field distribution of these modes for 2D slab waveguide can be expressed as:

wave transmission along slab waveguides, fibers & other type of optical waveguides can be fully described by time & z dependency of the mode:

,...TE,TE,TE 210

number) (mode 3,2,1,0

)ωcos()(e),,,(

m

ztyftzyxE mmxm

)(or )ωcos( ztjm

mezt

[2-26]

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TE modes in slab waveguide

z

y

number) (mode 3,2,1,0

)ωcos()(e),,,(

m

ztyftzyxE mmxm


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Modes in slab waveguide• The order of the mode is equal to the # of field zeros across the guide. The

order of the mode is also related to the angle in which the ray congruence corresponding to this mode makes with the plane of the waveguide (or axis of the fiber). The steeper the angle, the higher the order of the mode.

• For higher order modes the fields are distributed more toward the edges of the guide and penetrate further into the cladding region.

• Radiation modes in fibers are not trapped in the core & guided by the fiber but they are still solutions of the Maxwell’ eqs. with the same boundary conditions. These infinite continuum of the modes results from the optical power that is outside the fiber acceptance angle being refracted out of the core.

• In addition to bound & refracted (radiation) modes, there are leaky modes in optical fiber. They are partially confined to the core & attenuated by continuously radiating this power out of the core as they traverse along the fiber (results from Tunneling effect which is quantum mechanical phenomenon.) A mode remains guided as long as knkn 12

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Optical Fibers: Modal Theory (Guided or Propagating modes) & Ray Optics Theory

1n2n

21 nn

Step Index Fiber


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Modal Theory of Step Index fiber• General expression of EM-wave in the circular fiber can be written as:

• Each of the characteristic solutions is called mth mode of the optical fiber.

• It is often sufficient to give the E-field of the mode.

m

ztjmm

mmm

m

ztjmm

mmm

m

m

erVAtzrHAtzrH

erUAtzrEAtzrE

)ω(

)ω(

),(),,,(),,,(

),(),,,(),,,(

[2-27]

),,,( & ),,,( tzrHtzrE mm

1,2,3...m ),( )ω( ztjm

merU

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• The modal field distribution, , and the mode propagation constant, are obtained from solving the Maxwell’s equations subject to the boundary conditions given by the cross sectional dimensions and the dielectric constants of the fiber.

• Most important characteristics of the EM transmission along the fiber are determined by the mode propagation constant, , which depends on the mode & in general varies with frequency or wavelength. This quantity is always between the plane propagation constant (wave number) of the core & the cladding media .

),( rU m

m

)ω(m

knkn m 12 )ω( [2-28]

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• At each frequency or wavelength, there exists only a finite number of guided or propagating modes that can carry light energy over a long distance along the fiber. Each of these modes can propagate in the fiber only if the frequency is above the cut-off frequency, , (or the source wavelength is smaller than the cut-off wavelength) obtained from cut-off condition that is:

• To minimize the signal distortion, the fiber is often operated in a single mode regime. In this regime only the lowest order mode (fundamental mode) can propagate in the fiber and all higher order modes are under cut-off condition (non-propagating).

• Multi-mode fibers are also extensively used for many applications. In these fibers many modes carry the optical signal collectively & simultaneously.

cω

kncm 2)ω( [2-29]

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Fundamental Mode Field Distribution


Polarizations of fundamental modeMode field diameter

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Different Structures of Optical Fiber


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Mode designation in circular cylindrical

waveguide (Optical Fiber)

:modesEH Hybrid

:modesHE Hybrid

:modesTM

:modes TE

lm

lm

lm

lm The electric field vector lies in transverse plane.

The magnetic field vector lies in transverse plane.

TE component is larger than TM component.

TM component is larger than TE component.

l= # of variation cycles or zeros in direction. m= # of variation cycles or zeros in r direction.

x

y

r

z

Linearly Polarized (LP) modes in weakly-guided fibers ( )121 nn

)HETMTE(LP),HE(LP 000110 mmmmmm

Fundamental Mode: )HE(LP 1101

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Two degenerate fundamental modes in Fibers (Horizontal & Vertical Modes)

11HE


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Mode propagation constant as a function of frequency

• Mode propagation constant, , is the most important transmission characteristic of an optical fiber, because the field distribution can be easily written in the form of eq. [2-27].

• In order to find a mode propagation constant and cut-off frequencies of various modes of the optical fiber, first we have to calculate the normalized frequency, V, defined by:

ω)(lm

NA22 2

22

1

a

nna

V [2-30]

a: radius of the core, is the optical free space wavelength, are the refractive indices of the core & cladding.

21 & nn

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Plots of the propagation constant as a function of normalized frequency for a few of the lowest-order modes

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Single mode Operation• The cut-off wavelength or frequency for each mode is obtained from:

• Single mode operation is possible (Single mode fiber) when:

2

)ω( 2c22 c

nnkn

cclm

[2-31]

405.2V [2-32]

fiber optical along faithfully propagatecan HEOnly 11

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Single-Mode Fibers

• Example: A fiber with a radius of 4 micrometer and

has a normalized frequency of V=2.38 at a wavelength 1 micrometer. The fiber is single-mode for all wavelengths greater and equal to 1 micrometer.

MFD (Mode Field Diameter): It is an important parameter for single mode fiber.

• This parameter can be determined from the mode-field distribution of the fundamental fiber mode.

The electric field of the first fundamental mode can be written as:

min or frequency max @ 2.4 to2.3V

; m 12 to6 ; 1% to%1.0

a

498.1 & 500.1 21 nn

020

2

0 2MFD );exp()( WW

rErE [2-33]

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Birefringence in single-mode fibers

• Because of asymmetries the refractive indices for the two degenerate modes (vertical & horizontal polarizations) are different. This difference is referred to as birefringence, :fB

xyf nnB [2-34]


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Fiber Beat Length

• In general, a linearly polarized mode is a combination of both of the degenerate modes. As the modal wave travels along the fiber, the difference in the refractive indices would change the phase difference between these two components & thereby the state of the polarization of the mode. However after certain length referred to as fiber beat length, the modal wave will produce its original state of polarization. This length is simply given by:

fp kB

L2

[2-35]

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Multi-Mode Operation

• Total number of modes, M, supported by a multi-mode fiber is approximately (When V is large) given by:

• Power distribution in the core & the cladding: Another quantity of interest is the ratio of the mode power in the cladding, to the total optical power in the fiber, P, which at the wavelengths (or frequencies) far from the cut-off is given by:

2

2VM [2-36]

cladP

MP

Pclad

3

4 [2-37]

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Graded Index Fiber (GIN)• The most commonly used GIN have the index variation of

core as the power law given by

• No. of bounded modes in GIN fibr is

arfor 121)(

ar0for 21)(

212

1

1

21

1

nnnrn

a

rnrn

222

221

22 VnkaM g

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The mode field is defined as the distance between the points where the strength of the electric field is decayed to 0.37 (1/e) of the peak.

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FIBER MATERIALS In selecting materials following requirements must be satisfied1. It must b possible to make long, thin, flexible fibers fro the material

2. The material must be transparent at a particular wavelength in order for the fiber to guide light effectively.

3. Physically compatible materials that have slightly different refractive indices for the core and cladding must be available

Materials that satisfy these requirements are glasses and plastics

• Usually fibers are made of glass consisting of either silica SiO2 or silicate • Moderate loss fibers with large cores used for short-transmissions

• Low loss (very transparent) fibers are used for long-haul applications

• Plastics have higher attenuation than the glass fibers

• Plastic fibers are used in short distance fibers where more mechanical stresses are possible

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Glass Fibers

• Glass is made by fusing metal oxide, sulfides or selenides.• The resulting material is a randomly connected molecular network

called glass.• Glasses do not have well defined melting points • Melting point is defined as the temperature at which glass becomes

fluid enough to free itself of glass bubbles.• The largest category for optical fibers consists of oxide glasses.

• The most common of these oxides is the silica SiO2 which has refractive index of 1.458 at 850nm

• Fluorine or various oxides such as B2O3, GeO2, or P2O5 can be doped to slightly change the refractive index for the cladding

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• Plastic material

Plastic fibers are more economical over short distances for slower speeds.

Plastic fiber has poor optical qualities as compared to glass.

The cost and performance of plastic-clad Silica fiber is a compromise between the all-glass and all plastic fibers.

Plastic-Clad Silica Fiber. The above fiber uses a high quality glass core, clad

with a low cost plastic sheathing.

•Midway Solution

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• Since the cladding must have a lower refractive index as compared to the core so we can chose the following options for the doped materials

1. GeO2 – SiO2, core; SiO2 cladding

2. P2O5-SiO2, core; SiO2 cladding

3. SiO2 core; B2O3-SiO2 cladding

4. GeO-B2O3-SiO2 core; B2O3-SiO2 cladding

• Here the notation GeO2 – SiO2

denotes a GeO2 doped silica glass

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Properties of pure silica glass

• Pure silica is referred as silica glass, fused glass or vitreous silica

• Offer high resistance to deformation at high temperature as 1000oC

• High resistance to breakage from thermal shock because of its low thermal expansion

• Good chemical durability

• High transparency in both the visible and infra-red region

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ACTIVE GLASS FIBERS

• Incorporating rare earth elements (atomic numbers 57 - 71) converts normal passive glass fiber into new materials with new optical and magnetic properties.

• The new materials perform amplification, attenuation and phase retardation on the passing light

• Doping can be carried out for silica, tellurite and halide glasses

• Commonly used materials are Erbium and Neodymium

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Plastic Optical Fibers• High demand for delivering high speed services to the work station

require high bandwidth graded index polymer (plastic) optical fibers (POF).

• POF’s are used within the premises of user.• Fiber with core of polymethylmethacrylate referred as (PMMA POF) • Fiber with core of perfluorinated polymer is referred as PF POF• POF’s have greater attenuation as compared to glass fibers.• POF’s are tough and durable as compared to glass fibers• Modulus is two order of magnitude smaller than the glass fiber so

flexible to install.• Compared with glass fiber the core diameter is 10 – 20 times larger• Inexpensive plastic injection moulding technologies can be used to

fabricate connectors, splices and transceivers

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Photonic Crystal Fibers (PCF)

• Demonstrated in 1990, initially called holy fiber and later called Photonic Crystal Fiber (PCF)

• It has air holes run along the entire length of the fiber

• Sometimes air holes act as cladding known as Index-Guiding PCF

• Another form uses the band gap effect between the core as air holes and cladding known as photonic band gap fibers

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Fiber Fabrication

There are two basic techniques for fiber fabrication• Vapor-phase oxidation process• Direct melt methods

Direct melt methods :• Traditional glass making procedure , fibers are made from molten

state of purified silicate glass.

Vapor-phase oxidation process:

• Highly pure vapors of metal halides (SiCl4 and GeCl4) react with oxygen to form a white powder (SiO2).

• These particles are collected at the surface of the bulk glass by one of the four processes.

• These rods are then sintered and called preforms.

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• The preforms are around 10 – 25mm in dia and 60 – 120cm long

• Fibers are made from this preform using the fiber drawn equipment

• Drawing furnace bring it to the temperature where tip becomes soft and can be pulled through take-up drum

• Thickness depend on the speed of the drum

• Finally it is coated with the elastic material for protection

Fiber Drawing apparatus

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Outside Vapor-phase oxidation

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Vapor-Phase Axial Deposition (VAD)

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Modified Chemical Vapor Deposition (MCVD)

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Plasma –Activated Chemical Vapor Deposition (PCVD)

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Photonic crystal Fibers

Initially this was called holey fiber and later known as photonic crystal fiber (PCF) or a microstructured fiber.

There are two categories of photonic crystal fibers.

1. Index- Guiding PCF

2. Photonic Bandgap Fiber.

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Natural silicon dioxide SiO

2

Reduction ChlorinationDistillation

Silicon Tetrachloride (SiCl4)

Ultrapure silicon dioxide SiO

Fine particle mist with SiO

Oxidation in the vapor phase

Dry silicon dioxide SiO

Hydrolysis in thevapor phase

Dehydration

CO

FeClC,Cl

OHCl

H ,O

Cl HCl

3

Cl 2

2

2 2

2

22

2

2

Quartz and quartz mineral sands

Ultra pure silicon dioxide for use in fiber manufacture and integrated

circuits

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Vertical preform lathe Horizontal preform lathe

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Mechanical Properties of Fibers

Two basic mechanical characteristics of glass optical fibers are:

1. Strength

2. Static fatigue

Strength relates to instantaneous failure under an applied load.

Static fatigue relates to the slow growth of the pre existing flaws in the glass fiber under humid conditions and tensile stress.

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Fibers must be able to withstand :

1. Cable manufacturing process

2. Cable installation process

3. In service

1. Stresses2. Strains

During

Force applied to the fiber can either impulsive or gradually varying.


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Under applied stress:

•Glass will extend elastically up to its breaking strength.

•Metals can be stretched plastically well beyond their true elastic range

Copper wires can be elongated plastically by more that 20 percent before they fracture.

Glass fibers elongation of only 1 percent are possible before they fracture occurs.

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Microcrack model

A hypothetical model of a microcrack in an optical fiber

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Proof testing:

A high assurance of fiber reliability can be provided by proof testing.

In this method an optical fiber is subjected to a tensile

load greater than that expected at any time during the

cable manufacturing, installations, and service.

Any fibers that do not pass the proof test are rejected.

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Standard loose buffer tube type

Standard tight buffer (Bound) type

Fiber Ribbon

Classification on Cable StructureClassification on Cable Structure

Optical fiber cable

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Loose buffer tube

*Friction

The primary coated Fiber is laid loosely in a jelly filled narrow tube to prevent changes in the fiber’s optical properties due to

* Pressure

*Tensile stress

* Bends

* Torsion


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Loose buffer tube

Normally, there are only 4-6 fibers per tube.

The tube must conform to the following requirements.

* It must not deform through normal mechanical load.

* It must be durable.

* It must have low friction.

* It must withstand reasonably rough handling during installation, without changing the fiber’s optical properties.


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• Area of application

Loose tube fibers have been used very successfully in all areas of information transfer.

Used for long distance Networks


Loose buffer tube

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Tight Buffered FibersTight Buffered Fibers

The other alternative to protect the primary coated fiber is

achieved by applying a thick layer of plastic directly on the

245-500 m thick primary coated fiber.


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The tight buffer is color-coded according to a standard or customer’s specification.

Fiber 125 2 m

Primary coated fiber 245-500 m Color coded layer

900 m


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• Area of application

Local Area Networks (LAN) use almost exclusively tight buffered.

Advantages

Greatest area of application is indoors as connector cables and rack cables.

Easily terminated with a connector.

They are relatively easy to deal with during installation



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• Fiber Ribbon TechniqueFiber Ribbon Technique Third relatively new technique for adding buffer is to lay

several (2-12) primary coated fibers next to each other and then apply the additional coating.

Three methods for ribbon technique:

* Encapsulating

* Taping

* Edge bonding


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• Tapping: initial method

• Edge bounding: filling the Acrylate between the gapes

• Encapsulation: A layer of Acrylate is applied around the fibers

Fiber Ribbon TechniqueFiber Ribbon Technique


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The three most common methods of manufacturing fiber ribbon.

Taping

Edge Bonding

Encapsulation

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Breakout Cable (In door)

Simplex Cord

Duplex figure – 8 / Zip Cord

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Direct Burried CableDirect Burried Cable

PE outer sheath

PE inner sheath

Corrugated coated steel tape armour

Central strength member

Jelly filled loose tube

Moisture barrier sheath

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Aerial cable.

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Armored outdoor cable

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A typical range of armor protection cable

Irfan khan

Fiber optic underwater cable

Irfan khan

lightweight deep-water cable.

Irfan khan

Cable Jackets require a veriety of materials to best serve the environment to be used in.

These materials offer protection from the following concerns:

1. Mechanical

2. Chemical

3. Thermal

4. Environmental

Cable material

Irfan khan

* Direct burried application.

1. Polyethylene (PE)

A thermoplastic with good chemical and moisture resistance.

Application

* Aerial

2. Polyurethane (PU)

Application

A polymer with excellent abrasion resistance and low temperature flexibility.

* Excellent for duct.

Cable material

Irfan khan

* Duct environments

3. Polyvinyl Chloride (PVC) A thermoplastic with good flame and abrasion resistance.

Application* Raceways

4. Teflon.

A fluorocarbon / thermoplastic offers excellent properties in all cable categories except in radiation environments.

More costly than other cable material.

Cable material

Irfan khan

Kevlar

It is five times stronger than steel.

Protect fiber from moisture, chemicals and mechanical stresses placed on cable during installation, and splicing.

An aramid strength member.

Buffer Jacket (Tube)

Cable material

Irfan khan

Central member

Prevents buckling

Facilitates stranding Allows cable flexing Provides temperature stability

Cable material

Irfan khan

Strength member

Aramid Yarns (Kevlar)

Primary tensile load bearing member

Armoring (Burried Cable)

Protection from rodent attack and crushing forces.

Corrugated steel tape or multiple metal strands

Cable material

Irfan khan


Documents

Irfan khan OPTICAL FIBERS: STRUCTURES, WAVEGUIDING, AND FABRICATION