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Prof. Lian K Chen Part I. Fibers 1

IEG 4030 Optical Communications

Part I. Fibers

Professor Lian K. Chen

Department of Information Engineering

The Chinese University of Hong Kong

[email protected]

[For slide with * sign: supplemental material]

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Ref: [Keiser Ch2.1-2.3, 2.4*, 2.8*, 3.1, 3.2, 3.5.2-3 ][Agrawal Ch2.1-2.3 2.4*, 2.5]

Outline

Fiber basics

Fiber types

Ray theory

Basic EM wave theory Propagation mode

Single-mode and multimode fiber

Fiber attenuation

Signal distortion in fiber

Dispersion

Transmission system capacity

Fiber manufacturing

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IEEE Spectrum Feb. 2001

The hidden Hazard of Aging AircraftWiring

Pros and cons of fiber

Advantages:

low cost

small size, weight, flexibility

immunity to interference : no short circuit and crosstalk security

high bandwidth

low loss

stress and heat resistant

hazardous environment resistant

Disadvantage: difficult to tap light out

difficult to make connection

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Fiber Types

By refractive index profile

step-index fiber : the refractive index profile of fiber core is a step function

graded-index fiber : the refractive index of fiber core depends on the

radius distance.

By sustainable propagation mode

single-mode fiber : support only single propagation mode.

multi-mode fiber : support multiple propagation mode.

By dispersion characteristics non-dispersion-shifted fiber(NDSF) : standard single-mode fiber with zero

dispersion at 1.3m. [ITU-T G.652]

dispersion-shifted fiber(DSF) : zero dispersion at 1.55m. [ITU-T G.653]

non-zero dispersion shifted fiber(NZDSF) : small but non-zero dispersion

at 1.55m. [ITU-T G.655]

By polarization characteristics

polarization maintaining fiber : polarization preserved fiber

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Single-Mode Fiber Spool Multi-Mode Fiber Spool

Multi-Mode FiberPatchcord (Jumper)

Single-Mode FiberPatchcord (Jumper)

Fiber Types - 2

Notice the color difference!

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Fiber Types other specialty fibers

Photonic crystal fiber (PCF)

inculdephotonic-bandgap fiber(PCFs that confine light

by band gap effects), holey fiber(PCFs using air holes in

their cross-sections), hole-assisted fiber(PCFs guiding

light by a conventional higher-index core modified by thepresence of air holes), and Bragg fiber(photonic-bandgap

fiber formed by concentric rings of multilayer film).

Plastic optical fiber (POF)

larger core

much higher attenuation

easier for termination and splicing processing

Rare-earth doped fiber

e.g. for EDFA amplifiers

http://en.wikipedia.org/wiki/Photonic_crystal_fiber

http://en.wikipedia.org/wiki/Plastic_optical_fiber

http://en.wikipedia.org/wiki/Erbium-doped_fiber_amplifier

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Step Index

Pulse spreading in fibers

Graded Index

(1). multi-mode, step index fiber (2) multi-mode, graded index (3). single-mode, step index fiber

core

cladding

n1

n2

refractive

in

dex

core

cladding

n1

n2

refractive

in

dex

Step-index and Graded-index fiber

http://media.corning.com/flash/opticalfiber/2008/fiber101/fiber101.html

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Snells Law :

Note: if we increase1 to c such that

2

=90o

Ray theory valid if

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c=Set , then

2

12

2

2

12

1

2

1

21

2

1

2

1 )())(1()sin1( nnnnnn c ==

=in sin0

N.A.

1

21 )(

n

nn =Defined fractional index change

1/ 2

1N .A . (2 )n Larger N.A. more light collected.

But usually is chosen to be quite small,

~ 0.002 weakly guided

2

1

2112

1

21212

12

2

2

1 )](2[)]()([)( nnnnnnnnn +==for n1~n2

Ray Theory - 2

2

1

2

11110 )sin1(cos)2

(sinsinsin

==== nnnnn ri

loss (leaky and unguided)

ir

n2

n1Acceptance

angle

O.K.

core

cladding

n0

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Ray Theory - 3

Q. Whats wrong with strong guiding?

different arrival time

Large large N.A.

Large

large NAMultipathArray of

angles

wider acceptance angle

support an array of rays with different incident angles

multiple modes/ multipath

path length difference + different modes travel at different speeds

intermodal dispersion

signal pulse broadening

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Concept of an electric field E

If an electric fieldE exists in a certain region of space ,then every point (x,y,z) within the region is associatedwith a vector field E(x,y,z) such that when a test charge e

is brought to the point (x,y,z), it will experience a force

F = eE(x,y,z).

Concept of a magnetic f ield B

Similarly, if a region is associated with a magnetic fieldB, then a test charge in motion with velocity v will

experience a force F=evB(x,y,z) at every point (x,y,z)within .

The Lorentz force equation F=e(E+v B) describes thecombined effect of an electromagnetic field on a test

charge e.

e

F

E(x,y,z)

eF

B(x,y,z)v

Basic Electromagnetic Theory*

(bold face: a vector)

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Importance of the field concept

The electromagnetic phenomena arise from the interaction of charges.

With the concept of electromagnetic fields, one can study many

electromagnetic phenomena (such as the propagation of

electromagnetic waves) without having to worry about how they are

generated.

Unification of electricity and magnetism

Historically, electricity and magnetism were two different phenomena

in which many empirical relations had been discovered experimentally.

Maxwell unified them by introducing the concept of displacement

current to resolve the inconsistency in the equation of continuity. The

set of equations resulted is known as Maxwells equations.

Filed concept and unification of B and E*

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0

t

j

t

=

= =

= +

D

BB

E

DH

E and Hare the electric and magnetic field intensityD and B are the electric and magnetic flux density

D=E and B=H

andj are the charge density and current density.

and are thepermittivity andpermeability characterizing the electric and magnetic

properties of the medium. For isotropic media, and are scalars. In some

anisotropic media, and are tensors, denoted by and

Ref:

Ch4, Fiber-Optic Communications Technology D.K. Mynbaev and L.L. Scheiner, Prenctice Hall

Maxwells Equations (MKS Differential

Form)-1*

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Maxwells Equations (MKS Differential

Form)-2* In general, there are an infinite number of solutions to Maxwellsequations for any geometry and boundary conditions.

Under certain circumstances, the boundary conditions and the initial

field distribution may uniquely determine the EM field.

We usually consider only a few classes of solutions that represent

physical phenomena we are interested in. For example, in a

waveguide, we may be only interested in some of the propagating

modes.

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From Maxwells equation, one can derive the wave equations forlinear, isotropic and homogeneous medium:

Representation of a single-frequency wave and phase velocity

a general wave motion can be represented by sin(t-kz) or

is the temporal frequency andkis the spatial frequency (or propagation

vector, wave vector, wave number...)

temporal frequency denotes the number of repetitions of a wave per unittime

spatial frequency denotes the number of repetitions of a wave per unit

distance

The /kis known as the phase velocity; it is the velocity of anyconstant-phase point of a wave

2 22 2 2

2 2 2 2

1 1 10; 0; where c

c t c t

E HE H

= = =

( )i t k ze

EM Wave equation in isotropic,

homogeneous medium*

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The E field and H field of an EM wave are always orthogonal, either

component completely determines the other.

An EM wave propagates by exchanging energy between its E field and

H field (analogous to an LC oscillator). If E field is at the maximum, the

H field will vanish (and vice versa).

There are two independent polarizations for each monochromatic wave

with the same wave vector k because of the two spatial dimensions (xand y). When the phase difference between the two polarizations is

0o - the EM wave is plane-polarized

90o - the EM wave is circularly polarized

arbitrary - the EM wave is elliptically polarized

Reflection and refraction occur at the boundary interfaces - a result of

boundary condition for EM field.

Properties of electromagnetic waves

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+=

=

)cos(

)cos(

ztaE

ztaE

yy

xx

yExEyxE yx +=),(With

ztA =Let

=

=

+=

=

sinsincoscos

cos

)cos(

cos

AAa

E

Aa

E

AaE

AaE

y

y

x

x

yy

xx

2

22

22

22

22

2

22

2

sincos2

sinsincos2cos

sin1cos

sin1cos

=

+

=

+

=

=

yx

yx

y

y

x

x

x

x

yx

yx

y

y

x

x

x

x

y

y

x

x

x

x

x

x

y

y

aa

EE

a

E

a

E

a

E

aa

EE

a

E

a

E

a

E

a

E

a

E

aE

aE

a

E

Polarization Ellipse

Polarization of Light

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Polarization of Light -2

222

sincos2 =

+

yx

yx

y

y

x

x

aa

EE

a

E

a

EPolarization Ellipse:

Consider when =/2, gives 1

22

=

+

y

y

x

x

a

E

a

E

If ax=ay=a, the locus of the resultantE(x,y)will be a circle.

),( yxE

x

y

Circularly polarized/Circular polarization

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Circular Polarization

Polarization of Light - 3

See also http://webphysics.davidson.edu/physlet_resources/dav_optics/Examples/polarization.html

for some animation of polarization

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Polarizer in Photography

Use the Circular Polarizer or Linear Polarizer to block some of the

unwanted light

Also see http://www.geocities.com/COKINFILTERSYSTEM/polarizer.htm

Ref: National Geographic Photography Field Guide, ISBN 986-7680-46-4

with polarizer

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Whether a mode can be supported by the fiber described by two

parameters

: normalized propagation constant

If , these modes will not be supported cut off If

: normalized frequency

Note that a is the fiber core radius and where s thewavelength of the light.

2 2

2 2

2 2

1 2 1 2

( / ) /, for

12 2 2

1 2 1

2( ) ( ) 2V ka n n an

=

2 /k =

Propagation mode supported in Fiber

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Completely

cut off at b=0

guidedtightly

nn 1

Example: For a multimode fiber with n1=1.5, a=25 m, and =5x10-3, V is 18 for asource wavelength at 1.3 m. It will support ~ 162 modes.

2

~2

V

To have a single-mode

operation, V should be

2.405.

Note: large V large support more modes; and

the number of modes is

Supported propagation modes in fiber

Q: Why does fiber only support discrete modes?

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Comparison of Single- and multi-mode

fiberMulti-mode fiber (MMF) : larger core area easier for power coupling between source and

fiber or fiber to fiber.

can use LEDs as the light source; LED are easy to make, lessexpensive, require simpler circuitry, and have longer life time; but

bandwidth is limited.

Q: what are the cons?

Single-mode fiber (SMF) :

allows only one propagation mode no intermodal dispersion

(intermodal dispersion is caused by different propagation velocity for

different modes)

Note: Recent research on MMF has made high-speed communication

on MMF possible. We will come back to this later.

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Attenuation in Optical Fibers

Attenuation is measured in dB/km:

=

out

in

P

P

L10log

10

wherePin and Pout are the optical power into and out of the optical fiber,andL is the total length of fiber in km.

a

e

Attenuation spec. of Corning SMF-28 fiberThe ITU has specified six transmissionbands for fiber optic transmissions.

The six bands are theO-Band (1,260nm to 1,310nm),E-Band (1,360nm to 1,460nm),S-Band (1,460nm to 1,530nm),C-Band (1,530nm to 1,565nm),L-Band (1,565nm to 1,625nm),U-Band (1,625nm to 1,675nm).

A seventh band, not defined by the ITU, butused in private networks, runs around850nm.

In new fibers (Lucent All-Wave or Corning SMF-28e), OHabsorption peak around 1.4m has been largely suppressed.

We want to transmit signal at the

wavelength with small attenuation

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Causes of Fiber Attenuation

1. Material absorption: Silica (Intrinsic) and Impurities (Extrinsic) For SiO2, intrinsic absorption results from electronic absorption band in UV

( 7m) Impurities : Fe, Cu, Co, Ni, Cr. absorption

OH ions absorption at 2.7m. Harmonic tones occur at 1.4m, 0.95m,and 0.725m. Need to keep it below 1ppb.

2. Rayleigh scattering: Silica molecules move randomly in the molten state.

density fluctuations (~) cause Rayleigh scattering with scattering loss:

R=C/4 (C~0.7-0.9dB/km-m4)~ 0.12-0.16 dB/km at 1.55m

3. Waveguide Imperfections: Core radius variations scattering very small Bend loss can be high ~ e-R/Rc

R = radius of the fiber; Rc=a/(n12-n2

2);

For SMF, Rc=0.2-0.4mm. R>5mm.microbend

core

cladding

cladding

Density fluctuations

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Optical signal is distorted as it propagates along the fiber waveguide.

The distortion is due to intermodal dispersion, intramodal dispersion,

and polarization mode-dispersion .

All effects lead to ISI (inter-symbol interference) caused by pulsespreading, and subsequently limit the system transmission capacity.

t=0

t=t1

t=2t1

t=3t1

Evolution of pulse broadening

(Assume after t1, pulse width increases by

20% and pulse height reduces by 20%)

Signal distortion in optical waveguide

distance

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Intramodal dispersion

Intramodal dispersion

Intramodal dispersion or chromatic dispersion is the pulse spreading

occurs in a single propagation mode.

The pulse spreading is due to group velocity dispersion - signal atdifferent wavelength has different group velocity.

Intramodal dispersion consists of Material dispersion : caused by

the wavelength-dependence of

refractive index

Waveguide dispersion : causedby cladding mode (~20% for SM

fiber) which travels faster.

30

20

10

0

-10

-20

-301.1 1.2 1.3 1.4 1.5 1.6 1.7

Wavelength (m)

DM

DW

Dispersion

[ps/(km

nm)]

ZD

Dtotal

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20

10

0

-10

-20

1.1 1.2 1.3 1.4 1.5 1.6 1.7Wavelength (m)

standard fiber

dispersion f latten fiber

dispersion shif ted fiberDispersion

[ps/(km

nm)]

Dispersion-shifted fiber

For silica fiber,

Dmat (material dispersion) is a monotonically increasing function of .

Dwg (waveguide dispersion) is always

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Material dispersion (due to the frequency-dependent of the silica

fibers refractive index n)

2

2matd nD

c d

=

Material Dispersion

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2

2

2

1 ( )wg

n d VbD V

c dV

=

[Gloge Diagram]

LPjm modes

Waveguide Dispersion*

The effect of waveguide dispersion can be approximated by assuming

that the refractive index of the materials is independent of wavelength.

Dwg depends on the V parameter of the fiber

d(Vb)/d

V

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(c) triangular dispersion

shifted

(d) quadruple-clad

dispersion-flattened

(a) matched cladding

1300nm-optimized (b) depressed cladding

1300nm-optimized

Dispersion adjustment by refractive index

profile Various Refractive Index Profile to manipulate the fibers dispersion:

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Various fiber with different dispersions

Material dispersion can be changed by changing fiber glass doping

concentration

Waveguide dispersion can be changed by changing waveguide

geometry

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(Multipath dispersion)

The lights (rays) that enter the fiber at different angles will traverse

different distances inside the fiber.

The propagation time difference between the longest and shortest

paths is the Intermodal dispersion.

For step-index fiber :

c: critical angle

21 1

2c sin c

n L L nT L

c n = =

Modal dispersion

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Birefringence: f y xB n n=

Two modes propagate at different speeds.

PMD (polarization mode dispersion) occurs.

Birefringence

Even for single-mode fiber, there are two independent, degenerated

propagation modes.

These two modes are orthogonal in polarization.

In regular fiber, due to some imperfections (e.g. asymmetrical lateral

stress, noncircular core, or variations in refractive index), the refractive

indices for x and y direction are different .

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- Well defined, frequency independent eigenstates

- Deterministic, frequency independent Differential Group Delay (DGD)

- DGD scales linearly with fiber length

1st-order PMD

Ideal Practical

Core

Cladding

Cross-section of optical fiber

Fast axis

Slow axis

Fast

Slow

: Differential Group Delay (DGD)

Ref: Kazuo Yamane, Fujitsu

Polarization mode dispersion (PMD)

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PMD is caused by Fiber birefringence (difference in refractive indices

of two principle polarization states).

The fluctuation of PMD is due to the fluctuation of

signals principle states of polarization (PSP) or

differential group delay (DGD). (the delay difference between two

orthogonal mode of polarizations)

The mean PMD can be calculated by

where DPMD is the average PMD parameter measured in ps/(km)0.5 .

Typical DPMD ranges from 0.1 to 1 ps/(km)0.5

.

LDT PMDPMD

Ex

Ey

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PMD is an important factor for high speed (>10 Gb/s) systems.

Optical fibre cables covered by ITUG.652 recommendation generally have

a DPMD below 0.5 ps/km1/2.

This corresponds to a PMD-limited transmission distance of about 400 km

for STM-64 (10Gb/s) systems

For STM-256(40Gb/s), this distance is reduced to ~ 25 km!

PMD varies along the fiber and depends on the temperature.

PMD also depends on the fiber cable installation.

For example, in one experiment, the PMDs measured for a 36-km

spooled fiber, a 48.8-km buried cable, and a 48.8-km aerial cable

were 0.028, 0.29, and 1.28 ps/(km)0.5, respectively.

(Assume tolerable PMD is 10% of pulsewidth)

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group velocity vg :

group delayg :

Since the group velocity depends on the wavelength, a pulse that

contains different spectral components will spread out during

propagation.

Assume the is the spectral width of the pulse, the extent of pulsebroadening (T) for a fiber with length L is given by

where is known as GVD (group velocity dispersion) parameter.

11

=

dk

dcd

dvg

fiber)oflength:(

2

2

LL

d

d

cdk

d

c

L

v

L

g

g

===

==

==

22

2

Ld

dL

v

L

d

d

d

dTT

g

2

2

2

d

d

Group velocity dispersion

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More commonly, the spectral width is expressed in(unit: nm).

(Conversion ofand) Using or

the pulse spreading for an optical source with a spectral width isgiving by

where the dispersion parameterD is defined as

Note:As D can be positive or negative, we take the absolute value of Dto calculate the pulse spreading .

= ,)/2(

2 = c

g

dT d LT D Ld d v

= = =

i i

.1

gvd

dD

Group velocity dispersion (contd.)

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Assume infinitely extended dielectric medium with refractive index n()Then the propagation constant is given by

From the previous equation of the group delay g , the material dispersion(or group delay) can be derived as

Then the pulse spreadmat is given by

where2

2mat

d nD

c d

=

( )2 n

=

mat g

g

L L dn

nv c d

= = =

2

2( )mat

mat mat

d L d nL D

d c d

= =

Material Dispersion Derivation

(Note: pulse spectral width is also expressed as)

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Since all light sources have non-zero spectral width , the dispersioncannot be zero for all wavelength within .

The effective dispersion is D=S where is the dispersion

slope, differential dispersion parameter, or second-order dispersionparameter( note : Some people use D=0.5S )

From D, S can be derived as

Typical parameters of some commercial single-mode fibers

2 2 3

3 2(2 / ) (4 / )S c c = +

N.A. =(n1-n2)/n2(%)

2w(m)

ZD(m)

S[ps/(km-nm

2)]

Corning SMF-28

AT&T Matched-Clad

0.13

0.12

0.36

0.33

9.3

9.3

1.312

1.312

0.090

0.088

Corning SMF-DS

AT&T True Wave

0.17

0.16

0.90

0.75

8.1

8.4

1.550

1.530

0.075

0.095

d

dDS

Higher order dispersion*

where ( / )m mm

d d =

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(ITU-T G.652)

The maximum chromatic dispersion coefficient shall be specified by:

the allowed range of the zero-dispersion wavelength between 0min =1300 nm and

0max

= 1324 nm; the maximum value S0max= 0.093 ps/(nm2 km) of the dispersion slope at

zero dispersion wavelength. (shown as -0.093 in the standard document)

The chromatic dispersion coefficient limits for any wavelength within

the range 1260-1360 nm shall be calculated as:

( )4

0min0max1 34

SD

=

Dispersion specification of SM Fiber-1*

For a set of fibers with certain manufacturing tolerance:

( )4

0max0max2 34

SD

=

( )4

0 034

SD

=

If specific values (rather than a range

of values) of S0 and 0 are given,then D is in the form of :

(check corning SMF-28e spec sheet)

Di i ifi ti f SM Fib 2*

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The dispersion at 1500-1600nm for for a dispersion-shifted fiber

(Class IVb fiber specified in EIA) (or when is close to0)

The asumption is that the dispersion slope is constant around 0

( ) 0 0( )D S =

Dispersion specification of SM Fiber-2*

T i i t it

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For Gaussian input pulse, the output pulse width after passing through

a fiber is

where 0

is the r.m.s. pulse width of input Gaussian pulse and D

is

the pulse broadening due to fiber dispersion.

A commonly used criterion for the pulse broadening is

where TB is the bit period =1/Br and Bris the Bit rate (not bandwidth) of

the system.

Assume negligible initial pulse width, then

(For detail derivation under various conditions, see [Agrawal])

,)( 2/1220 D +=

,4/BT

)4/(1or4/1 DLBDLB rr

DLD=

-- bit-rate - distance product

Transmission system capacity

E l

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Example:

S t Si *

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For single mode fiber, the intensity distribution of the propagation

mode is important for characterizing the performance.

Ex can be approximated by a Gaussian distribution *.

[Agrawal]

By analytical fitting,

22

o

o

exp(- / )exp( ), where

- field radius = spot size

2 = mode filed diameter (MFD)

x oE A r w i z

w

w

=

-3/ 2 -6

o / 0.65 1.619 2.879w a V V + +

(* One of the various approximations.)

r=0

Spot Size*

Fiber drawing

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Fiber drawing

Various techniques for producing

optical fiber

Outside Vapor-Phase Deposition

(OVPD)

Vapor-Phase Axial Deposition (VAD) Modified Chemical Vapor

Deposition(MCVD)

Plasma-Activated Chemical Vapor

Deposition (PCVD)(see Kaiser)

Also seeCoring Fiber Manufacturing Demohttp://www.corning.com/cms/FlashVideoPlayer.aspx?id=39

597&ydistance=312

Preform feed

Furnace2000

C

Thicknessmonitoring gauge

Take-up drum

Polymer coater

Ultraviolet light orfurnace for curing

Capstan

Schematic illustration of a

fiber drawing tower. 1999 S.O. Kasap,Optoelectronics(Prentice Hall)

Outside vapor deposition

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Outside vapor deposition

Vapors: SiCl4+ GeCl4+O2

Rotate mandrel

(a)

Deposited soot

Burner

Fuel: H2

Target rod

Deposited Ge doped SiO2

(b)

Furnace

Porous sootpreform with hole

Clear solidglass preform

Drying gases

(c)

Furnace

Drawn fiber

Preform

Schematic illustration of OVD and the preform preparation for fiber drawing. (a)

Reaction of gases in the burner flame produces glass soot that deposits on to theoutside surface of the mandrel. (b) The mandrel is removed and the hollow porous soot

preform is consolidated; the soot particles are sintered, fused, together to form a clear

glass rod. (c) The consolidated glass rod is used as a preform in fiber drawing.

1999 S.O. Kasap, Optoelectronics (Prentice Hall)

Fiber Cable

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For practical application, fiber needs to be

encapsulated in cable for better protection.

Outer Sheath

Yarn strength

member

Buffer strength

member

Paper/Plastic

Binding Tape

Basic Fiber building

block

Insulator Copper

Conductor

Polyurethane/PVC

Jacket

Six-fiber cable

(See Coring Fiber Manufacturing Demo)

Fiber Cable

ITU T Recommendations

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ITU-T Recommendations

G.650 - Definition and test methods for the relevant parameters ofsingle-mode fibres

G.651 - Characteristics of a 50/125 m multimode graded index

optical fibre cable

G.652 - Characteristics of a single-mode optical fibre cable

G.653 - Characteristics of a dispersion-shifted single-mode optical

fibre cable

G.654 - Characteristics of a cut-off shifted single-mode optical fibrecable

G.655 - Characteristics of a non-zero dispersion shifted single-mode

optical fibre cable

Case Study flexible optical fiber

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Case Study flexible optical fiber

Question:

Fiber is made of glass. Can we make it very flexible for home cabling?

Solution: special fiber (e.g. Photonic Crystal Fiber or fiber with special

coating)

NTT - Fiber to the Home(FTTH) Project

Also see Corningsshowhttp://www.corning.com/optica

lfiber/library/videos.aspx

Photonic Crystal Fiber (Holey Fiber)*

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Photonic Crystal Fiber (Holey Fiber)

Applications

Dispersion compensation

White light (supercontinuum)

sources

Wavelength converters Hollow transmission fibers

Multi-core fiber couplers

Pulse shapers

Chemical sensors with long

interaction lengths

Temperature-insensitive PM

pigtails

Gyroscope fibers--athermal, and

highly birefringent

Pressure and temperature sensors

High Aeff and PM fibers for single-

mode interconnects

Mode converters http://www.blazephotonics.com/

Reading the Data Sheet

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Reading the Data Sheet

Corning SMF-28e+ optical fiberhttp://www.corning.com/WorkArea/showcontent.aspx?id=41261

Other interesting sites

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http://www.corning.com/opticalfiber/ (Corning Optical Fiber)

http://www.arcelect.com/fibercable.htm (The Basics of Fiber Optic

Cables: A tutorial)

http://www.sff.net/people/Jeff.Hecht/history.html (A short history offiber optics) and http://www.sff.net/people/Jeff.Hecht/chron.html (A

Fiber-Optic Chronology )

Other interesting sites

Documents

IEMS5705-part1.pdf