Optical Communication et4-013 B1

Optical Communication Systems

Opto-Electronic Devices GroupDelft University of Technology

Meint SmitXaveer Leijtens

Siang Oei

Course et4-013

Optical Communication et4-013 B2

Contents Introduction Fibre transmission properties Light sources (laser, LED) Light detectors Optical receivers Fibre systems

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Fibre performance

z=0 z=LDispersion

z=0 z=LAttenuation

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Fibre attenuation (SiO2)

1.80.8 1.0 1.2 1.4 1.60.9 1.1 1.3 1.5 1.7

Wavelength (m)

Atte

nuat

ion

(dB

/km

)

0.2

0.5

1.0

1.5

0.16 dB/km

Rayleighscattering

IR band edge

OH--peak

UVabsorption

Optical Communication et4-013 B5

Bandwidth and Bit rate

tT

FWHM

dBo0

-1.5-3

fofe

dBe0

-3-6

Idet = R·Popt (:) Pel

TBff

1

21

412 elopt

Rule-of-thumb:

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Types of dispersion

Intermodal dispersion only for MMF

Material Dispersion Chromatic Waveguide Dispersion Dispersion

Polarisation Mode Dispersion (PMD)

} {

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z=0

Chromatic dispersion

T

z=L

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Phase velocity (mode)

0dd t

ph0d

d)(dd

dd vt

zzttt

z

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Group velocity (pulse)

z

0dd t

dd0

dd)(

dd

dd

gr vtzzt

tt

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cnnc

2,2

dd

dd

dd

g

nncl

cnll

vlt

Material Dispersion (1)

dd

dd

dd nn

c2 22

dd

c

ddnnc

lt

Optical Communication et4-013 B11

Material Dispersion (2)

2

2

dd1

dd1 n

ctt

2

2

dd1

dd1 n

ct

llt

2

2

m dd

nc

D

ddnnc

lt

mDl

t

t

ddt

t

Optical Communication et4-013 B12

Material Dispersion (3)

-150

-100

-50

0

50

0.8 1 1.2 1.4 1.6

wavelength (m)

Dm (p

s/nm

/km

) `

Material Dispersion SiO2

1.272

2

m dd

nc

D

mDl

t

Optical Communication et4-013 B13

Standard Single-Mode Fibre

-60

-40

-20

0

20

40

1 1.1 1.2 1.3 1.4 1.5 1.6

wavelength (m)

D (p

s/nm

/km

) Dm SiO2

Dtot SSMF

Dw SSMF

1.3

\\

wmtot DDD

Optical Communication et4-013 B14

Fiber classification (1)

Core diameter 50 - 400 m

Cladding 125 (500) m

2nd coating 250 - 1000 m

NA 0.16 - 0.5

Attenuation 1 - 4 dB/km

BL-product 6 - 25 MHz.km

Application Short distance, low cost

limited bandwidth

MM-SI: Multi Mode - Step Index fiber

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Fiber classification (2)

Core diameter 50 m standard

Cladding 125 m

2nd coating 200-1000 m

NA 0.2 - 0.3

Attenuation 1 dB/km (1300 nm)

BL-product 150 MHz.km - 2 GHz.km

Application Medium distance communication

LED/Laser sources

MM-GI: Multi Mode - Graded Index fiber

Optical Communication et4-013 B16

Fiber classification (3)

Core diameter 3-10 m

Cladding 50-125 m

2nd coating 200-1000 m

NA ~0.1 (not used)

Attenuation 0.20@1550 - 0.4@1300 dB/km

BL-product >> 500 MHz.km

Application Long distance communication

Lasers, standard fiber

SM-SI: Single Mode - Step Index fiber

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Waveguide dispersion

n1 ()n2 ()

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Dispersion shifted fibre

-60

-40

-20

0

20

40

1 1.1 1.2 1.3 1.4 1.5 1.6

wavelength (m)

D (p

s/nm

/km

) Dm SiO2

Dtot DSF

Dw DSF

1.55

\\

wmtot DDD

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Dispersion Mechanisms

Intermodal

multimode fiber!

Intramodal / Chromatic

• materialn

• waveguide

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Optimal Pulse Width

20

2

20)(

t

et

041

f

cfc

dfd

fc 2

2

0

22

4dd

ccf ff

222tot

20

2t

20

2 lD 20

22

242tot2

02

16 clD

-3 -2 -1 0 1 2 3

clD

22 tot

0min

Gaussian pulse:

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Soliton Transmission2

20 || Ennn

t

0

0.5

1

-3 -2 -1 0 1 2 3

)/(sech)( 20 Ttt

202

2tot

3

2 EcnDT

Etot=2 TFWHM=1.76Tn(E)

Pulse Compression

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Erbium-Doped Fiber Amplifier (EDFA)

PUMP LASER 0.98 m or 1.48 m

Er-doped fiber

MUX FILTER

-10

0

10

20

30

1520 1530 1540 1550 1560 1570

wavelength (nm)

EDFA

gai

n (d

B)