Optical Communication File

7/23/2019 Optical Communication File

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RAYAT BAHRA INSTITUTE OF

ENGINEERING AND BIO-TECHNOLOGY

Department of Electronic ! Comm"nication En#ineerin#

O$TICAL CO%%UNICATION LAB

Submitted To: Submitted By:

Er. Rupali Kamboj Gagan Maggo

ECE 7A

1!7"#"



Ta&le of Content

Sr' No Topic $a#e

No'

1.

.

$.

!.

%.

&.

Study and mea'urement o( attenuation and lo'' in opti)al

(iber.

Study and mea'urement o( bending lo'' in opti)al (iber

Study and mea'urement o( numeri)al aperture o( opti)al

(iber.

Mea'urement o( opti)al po*er u'ing opti)al po*ermeter.

To 'tudy t+e tran'mi''ion o( T,M 'ignal t+roug+

opti)al (iber

Study -ariou' multipleing te)+ni/ue'.



E($ERI%ENT No') *

Aim ) St"+, an+ mea"rement of atten"ation an+ lo in optical fi&er

Equipments Required•

S)iente)+ %#1A Te)+Boo0 *it+ o*er Supply and main' )ord•

2pti)al 3ibre )able

S)iente)+ 2')illo')ope

THEORY)-

4+en t+e lig+t )ro''e' an ab'orbing medium5 a' in t+e )a'e o( opti)al (iber5 t+e luminou'

energy de)rea'e a' di'tan)e in)rea'e'. T+e lo'' in a (iber lengt+ atten"ation. i' epre''ed by

t+e ratio bet*een t+e po*er entering one end o( t+e (iber 6 89 and po*er )oming out (rom

t+e oppo'ite end 6out9. Attenuation i' normally mea'ured in de)ibel:

Att 6dB9 1# log 6out;in9t )an range' (ro 'ome db;m (or pla'ti) (iber 5to (ra)tion o( db;0m (or gla'' (iber'.

T+e attenuation o( t+e lig+t 'ignal due to t+e (iber' depend' on t+e *a-e lengt+ and on t+e

material *+i)+ t+e (iber +a' been )on'tru)ted *it+ . n gla'' (iber t+e main )au'e' o(

attenuation are t+e ab'orption lo''e' and t+e ')attering lo''e'. Combining t+e'e lo''e' lead to

plotting t+e intrin'i) attenuation )ur-e li0e t+at '+o*n in t+e (ig 1 *+erea' t+e (ig '+o*n t+e

attenuation )ur-e o( a pla'ti) (iber. 3ollo*ing lo''e' lead' to attenuation

A&orption lo) 4+en t+e lig+t p+oton' +a-e a )ertain -alue o( energy5 t+e atom' o( gla'' o(

t+e )ore 6Si29 ab'orb a part o( t+i' energy. T+i' p+enomenon depend' on *a-elengt+ and

t+ere are t*o di((erent ab'orption <one'5 o))urring in t+e in(rared 'pe)trum and in t+e ultra

-iolet 'pe)trum. 3urt+ermore5 during t+e )+emi)al pro)e'' o( gla'' manu(a)turing5 -ariou'

metalli) impuritie' are trapped in t+e )ore5 among t+e'e impuritie' t+ere are al'o 'ome ion'

2=> *+i)+ pro-o0e ab'orption pea0' at di')rete -alue o( *a-elengt+.

Scatterin# lo) T+ey are due to t+e granular 'tru)ture 6at mi)ro')opi) le-el9 o( t+e material

*+i)+ t+e (iber i' )on'tru)ted *it+. T+i' 'tru)ture in)lude' 'ome ')attering )enter' *+i)+ are

material point t+at ')atter t+e radiation in all dire)tion'5 e-en ba)0*ard' t+i' p+enomenon i'

)alled Rayleigh catterin# or material ')attering.

Ot/er loe: n an opti)al (iber lin05 ot+er )an be due to too narro* loop' in t+e pat+ o( t+e

opti)al )able 6Bending lo''e'95 or to jun)tion o( more lengt+' o( (iber. 2( )our'e t+ey are not

intrin'i) lo''e' o( t+e (iber5 but t+ey depend on )able laying.

Procedure:

Conne)t t+e Te)+Boo0 o*er Supply *it+ main' )ord to Te)+Boo0 S)iente)+

%#1A.

Ma0e t+e )onne)tion' a' '+o*n in net (igure

Conne)t t+e 3un)tion Generator 1 K=< 'ine *a-e output to emitter input.

Conne)t #.% m opti) (iber bet*een emitter output and dete)tor input.

Conne)t ,ete)tor output to ampli(ier input.ut t+e mode '*it)+ S41 to Analog to dri-e t+e

emitter in analog mode. S*it)+ ?2n@ t+e o*er Supply o( Te)+Boo0 and 2')illo')ope.



Tou)+ t+e o*er 'ymbol (or (e* 'e)ond' to '*it)+ on t+e Te)+Boo0. o*er 'ymbol i'

gi-en at e(t 'ide top po'ition o( mimi) near t+e o*er Conne)tor.

Set t+e 2')illo')ope )+annel 1 to #.% ; ,i- and adju't !>& di- amplitude by u'ing 1

probe *it+ t+e +elp o( -ariable potentiometer in 3un)tion Generator blo)0 at input o( emitter.

2b'er-e t+e output 'ignal (rom dete)tor on 2')illo')ope.

Adju't t+e amplitude o( t+e re)ei-ed 'ignal a' t+at o( tran'mitted one *it+ t+e

+elp o( gain adju't' pot in AC ampli(ier blo)0. 8ote t+i' amplitude and name it V 1.

8o* repla)e t+e pre-iou' (iber opti) )able *it+ 1 m )able *it+out di'turbing any pre-iou'

'etting.

Mea'ure t+e amplitude at t+e re)ei-er 'ide again at output o( ampli(ier. 8ote t+i' -alue end

name it V . Cal)ulate t+e propagation 6attenuation9 lo'' *it+ t+e +elp o( (ollo*ing (ormula.

1; e >D619

4+ere D lo'' in neper' ; meter

1 neper' ".&"& dB1 lengt+ o( '+orter )able 6#.% m9

engt+ o( longer )able 61 m9



E($ERI%ENT No')0

Aim) St"+, an+ mea"rement of &en+in# lo in optical fi&er

Equipments Required: •

S)iente)+ %#1A Te)+ Boo0 *it+ o*er Supply and main' )ord•

2pti)al 3iber )able

S)iente)+ 2')illo')ope

Mandrel

T/eor,)-

4+ene-er t+e )ondition (or angle o( in)iden)e o( t+e in)ident lig+t i' -iolated t+e lo''e' are

introdu)ed

due to re(ra)tion o( lig+t. T+i' o))ur' *+en (iber i' 'ubje)ted to bending. o*er t+e radiu' o(

)ur-ature more i' t+e lo''.



Procedure:

Conne)t t+e Te)+Boo0 o*er Supply *it+ main' )ord to Te)+Boo0 S)iente)+ %#1A.

Ma0e t+e )onne)tion' a' '+o*n in net (igure

Conne)t 3un)tion Generator 1 K=< 'ine *a-e output to emitter input.

Conne)t #.% m opti) (iber bet*een emitter output and dete)tor' input.

Conne)t ,ete)tor output to ampli(ier input

ut t+e mode '*it)+ S41 to Analog to dri-e t+e emitter in analog mode.

S*it)+ ?2n@ t+e o*er Supply o( t+e Te)+Boo0 and 2')illo')ope.

Tou)+ t+e o*er 'ymbol (or (e* 'e)ond' to '*it)+ on t+e Te)+Boo0. o*er 'ymbol i' gi-en

at e(t 'ide top po'ition o( mimi) near t+e o*er Conne)tor.

Set t+e 2')illo')ope )+annel 1 to #.% ; ,i- and adju't !>& di- amplitude by u'ing 1 probe*it+ t+e +elp o( -ariable pot in 3un)tion Generator Blo)0 at input o( Emitter.

2b'er-e t+e output 'ignal (rom dete)tor on 2')illo')ope.

Adju't t+e amplitude o( t+e re)ei-ed 'ignal a' t+at o( tran'mitted one *it+ t+e +elp o( gain

adju't' potentiometer in AC ampli(ier blo)0. 8ote t+i' amplitude and name it 1.

4ind t+e (iber opti) )able on t+e mandrel and ob'er-e t+e )orre'ponding AC ampli(ier output

on 2')illo')ope5 it *ill be gradually redu)ing5 '+o*ing lo'' due to bend'.



E($ERI%ENT No') 1

Aim) St"+, an+ mea"rement of n"merical apert"re of optical fi&er'

Equipments Required:

S)iente)+ %#1A Te)+ Boo0 *it+ o*er Supply and main' )ord2pti)al 3iber )able

8umeri)al Aperture mea'urement Fig

THEORY)-

8umeri)al Aperture i' de(ined a' t+e lig+t gat+ering )apability o( t+e (iber

Mat+emati)ally gi-en by:

8A Sin ØA

Sin ØA 6,;9

4+ere:

i' t+e di'tan)e bet*een t+e )able end and t+e mea'urement ben)+ #mm

, i' t+e diameter o( t+e a))eptan)e )one

Procedure:

Conne)t t+e Te)+Boo0 o*er Supply *it+ main' )ord to Te)+Boo0 S)iente)+ %#1A.

ut t+e mode '*it)+ S41 to ,igital to dri-e t+e emitter in digital mode.

S*it)+ ?2n@ t+e o*er Supply o( Te)+Boo0 and 2')illo')ope.

Tou)+ t+e o*er 'ymbol (or (e* 'e)ond' to '*it)+ on t+e Te)+ Boo0. o*er 'ymbol i' gi-en


Conne)t t+e 3re/uen)y Generator 1 K=< 'ine *a-e output to input o( emitter )ir)uit. Adju't

it' amplitude at % p>p. .

Conne)t one end o( (iber )able to t+e output 'o)0et o( emitter )ir)uit and t+e ot+er end to

t+e numeri)al aperture mea'urement jig. =old t+e *+ite ')reen (a)ing t+e (iber 'u)+ t+at it'

)ut (a)e i' perpendi)ular to t+e ai' o( t+e (iber.

=old t+e *+ite ')reen *it+ ! )on)entri) )ir)le' 61#5 1%5 # H % mm diameter9 -erti)ally at a



'uitable di'tan)e to ma0e t+e red 'pot (rom t+e (iber )oin)ide *it+ 1# mm )ir)le.

Re)ord t+e di'tan)e' o( ')reen (rom t+e (iber end and note t+e diameter 4 o( t+e 'pot.

Compute t+e numeri)al aperture (rom t+e (ormula gi-en belo*.

N.A= W/(4L2+W2)1/2

= Sin өmax (Acceptance angle)

ary t+e di'tan)e bet*een in ')reen and (iber opti) )able and ma0e it )oin)ide *it+ one o( t+e

)on)entri) )ir)le'. 8ote it' di'tan)e.

Tabulate t+e -ariou' di'tan)e' and diameter o( t+e )ir)le' made on t+e *+ite ')reen and

)omputer t+e numeri)al aperture (rom t+e (ormula gi-en abo-e.

Questions:

4+at i' numeri)al apertureI4rite t+e (ormula (or numeri)al apertureI

4+at i' t+e 'igni(i)an)e o( numeri)al apertureI



E($ERI%ENT No') 2

Aim) %ea"rement of optical po3er "in# optical po3er meter'

Equipments Required:

•S)iente)+ %#1A Te)+Boo0 *it+ o*er Supply and main' )ord

•2pti)al 3ibre )able

•S)iente)+ 2')illo')ope

•S)iente)+ %%1 > 2pti)al o*er Meter

Procedure:

•Conne)t t+e Te)+Boo0 o*er Supply *it+ main' )ord to Te)+Boo0 S)iente)+ %#1A.

•En'ure t+at all '*it)+ed (ault' are ?2((@.

•Conne)t t+e (iber opti) )able bet*een emitter output H po*er meter.

•ut t+e mode '*it)+ in emitter blo)0 to analog mode.

•

Conne)t t+e S)iente)+ %%1 2pti)al o*er Meter to emitter input.



•Keep t+e po*er meter *a-elengt+ 'ele)tor '*it)+ in &&# nm.

•S*it)+ ?2n@ t+e o*er Supply o( t+e Te)+Boo0 and o*er meter.

•Tou)+ t+e o*er 'ymbol (or (e* 'e)ond' to '*it)+ on t+e Te)+Boo0. o*er 'ymbol i' gi-en


• 8ote t+e reading di'played in po*er meter.

•S*it)+ t+e *a-elengt+ 'ele)tor '*it)+ to J%# nm po'ition'.

•Again note t+e reading di'played on po*er meter.



E($ERI%ENT No') 4

Aim :To t"+, t/e tranmiion of TD% i#nal t/ro"#/ optical fi&er

A$$ARTUSE)

1. T,M AM Trainer 0it.

. 3iber 2pti) Trainer Kit.

$. 3iber 2pti) lin0

!. Conne)ting *ire'.

%. 2')illo')ope.

THEORY)

INTRODUCTION TO $ULSE A%$LITUDE %ODULATION

Mo't digital modulation 'y'tem' are ba'ed on pul'e modulation. t in-ol-e' -ariation o( a

pul'e parameter in a))ordan)e *it+ t+e in'tant -alue o( t+e in(ormation 'ignal. T+i'

parameter )an be amplitude5 *idt+5 repetiti-e (re/uen)y et). ,epending upon t+e nature o(

parameter -aried5 -ariou' modulation 'y'tem' are u'ed. ul'e Amplitude Modulation5 ul'e

*idt+ Modulation5 ul'e Code Modulation are (e* modulation 'y'tem' )ropping up (rom t+e

pul'e modulation te)+ni/ue. n pul'e amplitude modulation 6AM9 t+e amplitude o( t+e

pul'e' are -aried in a))ordan)e *it+ t+e modulating 'ignal. n true 'en'e5 ul'e Amplitude

Modulation i' analog in nature but it (orm' t+e ba'i' o( mo't digital )ommuni)ation and

modulation 'y'tem'. T+e pul'e modulation 'y'tem' re/uire analog in(ormation to be 'ampled

at predetermined inter-al' o( time. Sampling i' a pro)e'' o( ta0ing t+e in'tantaneou' -alue o(

t+e analog in(ormation at a predetermined time inter-al.

T+e re)ei-er )an re)on'tru)t t+e 'ignal (rom t+e'e 'ample'5 pro-ided t+e 'ampling meet' t+e 8y/ui't )riteria. 8y/ui't )riteria 'tate' t+at (or a band limited 'ignal *it+ +ig+e't (re/uen)y

)omponent fm5 t+e 'ignal mu't be 'ampled at a rate greater t+en t*i)e t+e +ig+e't (re/uen)y

)omponent in t+e 'ignal (or t+e 'ampled 'ignal to be re)o-ered ea)tly i.e. f 6 0fm 3/ere f

7 amplin# fre8"enc, T+e pul'e amplitude modulation 'y'tem )an be 'imulated a' '+o*n in

3ig. 1.



T+e )ontrol 'ignal i' totally ele)tri)ally i'olated (rom t+e in(ormation 'ignal. Al'o t+e '*it)+

i' )on'idered ideal i.e.

i. t '+ould o((er negligible re'i'tan)e5 *+en )lo'ed and '+ould +a-e in(inite re'i'tan)e *+en

open.

ii. T+e opening and )lo'ing operation' are delay (ree.iii. T+e '*it)+ i' (ree o( )onta)t boun)e problem.

T+e )ontrol 'ignal )lo'e' t+e '*it)+ *+en it i' at one le-el and open' it *+en it i' at anot+er.

4+en t+e '*it)+ i' )lo'ed t+e output -oltage i' e/ual to Lero -olt'. T+e *idt+ o( t+e 'ample

depend' upon t+e time duration (or *+i)+ t+e '*it)+ remained )lo'ed. n pra)ti)e5 t+e '*it)+

i' operated ele)tri)ally. The resulting PAM wave is as shown in Fig. .

Be)au'e o( it' *ideband and analog nature5 AM +a' >re'tri)ted o( appli)ation' (or dire)t

tran'mi''ion o( 'ignal'. t i' u'ed5 (or eample in in'trumentation 'y'tem' and in A;,

Con-erter' u'ed (or )omputer inter(a)ing. t i' al'o u'ed a' an intermediate 'tage in t+e

generation o( -ery popular digital modulation 'y'tem -i<. CM 6ul'e Code Modulation.9

Anot+er ad-antage o( AM i' t+at it allo*' (or multipleing o( t+e 'ignal'.

%"ltiple9in#)

Multipleing i' t+e pro)e'' o( )ombining 'ignal' (rom di((erent in(ormation 'our)e' o( t+at

t+ey )an be tran'mitted o-er a )ommon )+annel. Multipleing i' ad-antageou' in )a'e' *+ere

it i' impra)ti)able and une)onomi)al to pro-ide 'eparate lin0' (or t+e di((erent in(ormation

'our)e'. T+e pri)e t+at +a' to be paid to a)/uire t+i' ad-antage i' in t+e (orm o( in)rea'ed

'y'tem )ompleity and band*idt+.

T/e t3o mot commonl, "e+ met/o+ of m"ltiple9in# are)

*. 3re/uen)y di-i'ion multipleing 63,M9

0. Time di-i'ion multipleing 6T,M9

Time Di:iion %"ltiple9in#)



Time ,i-i'ion Multipleing i' t+e pro)e'' o( )ombining t+e 'ample' (rom di((erent

in(ormation 'ignal'5 in time domain 'o t+at t+ey )an be tran'mitted o-er t+e 'ame )+annel.

T+e (a)t utili<ed in T,M te)+ni/ue i' t+at t+ere large inter-al' bet*een t+e me''age 'ample'.

T+e 'ample' (rom t+e ot+er 'our)e' are pla)ed *it+in t+e'e time inter-al'. T+u' e-ery 'ample

i' 'eparated (rom ot+er in time domain.

T+e time di-i'ion multipleing 'y'tem )an be 'imulated by t*o rotating '*it)+e'5 one at

tran'mitter and t+e ot+er at re)ei-er. 6See 3ig. !.9 T+e t*o *iper' rotate and e'tabli'+

ele)tri)al )onta)t *it+ one )+annel at a time.

Ea)+ 'ignal i' 'ampled o-er one 'ampling inter-al and tran'mitted one a(ter t+e ot+er along a

)ommon )+annel. T+u' part o( me''age 1 i' tran'mitted (ir't (ollo*ed by part o( me''age 5

me''age $$ and t+en again me''age 1 'o on.

t )an be anti)ipated (rom abo-e pro)e'' t+at t+e re)ei-er '*it)+ +a' to (ollo* t*o

)on'traint':

*. t mu't rotate at t+e 'ame rate a' t+e tran'mitter '*it)+.

0. t mu't 'tart at t+e 'ame time a' t+e tran'mitting '*it)+ and it mu't e'tabli'+ ele)tri)al

)onta)t *it+ t+e 'ame )+annel no. a' t+at o( t+e tran'mitter. ( t+e'e t*o )ondition' are met5

t+e re)ei-er i' 'aid to be in 'yn)+roni<ation *it+ tran'mitter. ( )on'traint one i' not met5 t+e

'ample' o( di((erent 'our)e' *ould get mied at t+e re)ei-er. ( )on'traint t*o i' not met5 t+e

in(ormation (rom 'our)e 1 *ill be re)ei-ed by 'ome ot+er )+annel *+i)+ i' not intending to

a))ept t+e in(ormation (rom t+at parti)ular )+annel. To e'tabli'+ 'yn)+roni<ation5 t+e re)ei-er need' to 0no*:

*. (re/uen)y;rate o( operation at tran'mitter.



0. Sample identi(i)ation. T+i' in)rea'e' t+e tran'mitter and re)ei-er )ompleity and )o't.

$ractical Apect of Time Di:iion %"ltiple9in#)

n time di-i'ion multipleing t+e )orre)t operation' o( tran'mitter '*it)+ *+i)+ )reate'

'ample'5 i' a mu't. T+e (un)tioning o( T,M '*it)+ i' )omple. But it' under'tanding i' ea'y5

pro-ided you are a*are o( t+e ei'ten)e o( )ir)uit delay' and 'etting time'. T+eoreti)ally

large number o( 'ample' )an be multipleed in time domain5 but it' pra)ti)al implementation

be)ome' +arder and +arder a' t+e time inter-al bet*een )on'e)uti-e 'ample' de)rea'e'. n ST

1# trainer5 t+e operation' o( tran'mitter '*it)+ are )ontrolled by t+e tran'mitter timing

logi). 6See 3ig &9



SYNCHRONI;ATION

T+e mo't -ital re/uirement o( a time di-i'ion multipleed 'y'tem i' 'yn)+roni<ation. T+e

tran'mitter and re)ei-er are 'aid to be 'yn)+roni<ed *+en:

619 T+e rate o( operation at tran'mitter i' 'ame a' t+e rate o( operation at re)ei-er.

69 Sample' )an be identi(ied *it+ di((erent )+annel' i.e. time'lot # 'ample' mu't go to

)+annel # output5 time'lot 1 'ample' mu't go to )+annel 1 output and 'o on.

T+e )ir)uitry t+at generate' t+e timing 'ignal (or t+e 'y'tem i' )alled )lo)0. 2(ten t+e )lo)0

generate' periodi) re)tangular pul'e' and +en)e are 0no*n a' )lo)0 pul'e'. T+e /ue'tion mayari'e *+y i' t+e )lo)0 'o importantIN

A' *e 0no*5 t+e time di-i'ion multipleing and demultipleing re/uire' a parti)ular

operation to o))ur on t+e pre)i'e time inter-al. 3ailure to meet t+i' re/uirement lead' to

'ignal )orruption5 di'tortion and e-en )omplete 'y'tem brea0do*n. T+e )ir)uit *+i)+ en'ure'

pre)i'ely timed a)tion i' t+e )lo)0 )ir)uit. All t+e time related pro)e''e' deri-e t+e timing

dire)tly or indire)tly (rom t+e 'y'tem )lo)0. 3or )orre)t operation o( re)ei-er5 t+e '*it)+ing

rate '+ould be 'ame a' t+at (or tran'mitter. To do t+i' t+e re)ei-er )lo)0 mu't mat)+ *it+ t+e

tran'mitter )lo)0.

Be'ide' )lo)0 'ignal5 t+e re)ei-er al'o re/uire' in(ormation (rom t+e tran'mitter to identi(y

one Time'lot per (rame and 'o a' to pa'' t+e time 'lot to )orre)t output )+annel. ( it i'

a)+ie-ed (or one time'lot. t+en ot+er time'lot' in t+e (rame are pa''ed to t+e )orre)t )+annel'.

t i' en'ured by (rame 'yn)+roni<ation 'ignal. T+e'e t*o 'ignal' namely t+e )lo)0 'ignal and

3rame 'yn)+roni<ation 'ignal '+ould be tran'mitted by t+e tran'mitter along *it+ t+e

in(ormation 'ignal. T+e ST 1# pro-ide' you t+e (leibility o( u'ing t+ree di((erent mode' o(

t+e'e in(ormation tran'(er'.

Mode 1 : T+ree lin0' bet*een tran'mitter H Re)ei-er 6,iagram A9

It #i:e rie to t/e mot imple recei:er circ"itr,' In t/i mo+e a eparate tranmiion

me+ia are "e+ to carr, t/e information i#nal5 t/e cloc< i#nal5 an+ t/e Frame

,nc/roni=ation i#nal'



$ROCEDURE)

1. Conne)t t+e po*er 'upply to t+e board.

. En'ure t+at all '*it)+ed (ault' are o(( in T,M AM H 3iber 2pti) Trainer Kit.

$. Ma0e t+e (ollo*ing )onne)tion'. 6A' '+o*n in ,iagram 19

!. Conne)t t+e 3un)tion Generator %#=<5 %##=<5 1 K=< H K=< 'ine *a-e output to C=#5

C=15 C= H C=$ in T,M AM Tran'mitter.

%. T,M AM Tran'mitter output Conne)t' emitter 1 O' input.

&. t+e 3iber 2pti) )able Conne)t' bet*een emitter output and dete)tor' input.

7. ,ete)tor 1O' output gi-en to Comparator.

". 2utput o( Comparator i' gi-en to Re)ei-er nput and demodulated output ob'er-ed.

J. Conne)t T Clo)0 H T Syn) *it+ Re)ei-er in T,M AM Trainer 0it.

1#. 2n t+e board5 '*it)+ emitter 1O' dri-er to Analog mode.

11. S*it)+ 28 t+e po*er.



E($ERI%ENT No') >

Aim) St"+, :ario" m"ltiple9in# tec/ni8"eE?UI$%ENT)-

Edu)ational Trainer Board.

Cable'

THEORY)-@a:elen#t/ Di:iion %"ltiple9in#)

4,M enable' t+e utili<ation o( a 'igni(i)ant portion o( t+e a-ailable (iber band*idt+ by allo*ing

many independent 'ignal' to be tran'mitted 'imultaneou'ly on one (iber5 *it+ ea)+ 'ignal lo)ated

at a di((erent *a-elengt+. Routing and dete)tion o( t+e'e 'ignal' )an be a))ompli'+ed

independently5 *it+ t+e *a-elengt+ determining t+e )ommuni)ation pat+ by a)ting a' t+e

'ignature addre'' o( t+e origin5 de'tination or routing. Component' are t+ere(ore re/uired t+at are

*a-elengt+ 'ele)ti-e5 allo*ing (or t+e tran'mi''ion5 re)o-ery5 or routing o( 'pe)i(i) *a-elengt+'.

n a 'imple 4,M 'y'tem5 ea)+ la'er mu't emit lig+t at a di((erent *a-elengt+5 *it+ all t+e la'er'

lig+t multipleed toget+er onto a 'ingle opti)al (iber. A(ter being tran'mitted t+roug+ a +ig+> band*idt+ opti)al (iber5 t+e )ombined opti)al 'ignal' mu't be demultipleed at t+e re)ei-ing end

by di'tributing t+e total opti)al po*er to ea)+ output port and t+en re/uiring t+at ea)+ re)ei-er

'ele)ti-ely re)o-er only one *a-elengt+ by u'ing a tunable opti)al (ilter. Ea)+ la'er i' modulated

at a gi-en 'peed5 and t+e total aggregate )apa)ity being tran'mitted along t+e +ig+>band*idt+

(iber i' t+e 'um total o( t+e bit rate' o( t+e indi-idual la'er'. An eample o( t+e 'y'tem )apa)ity

en+an)ement i' t+e 'ituation in *+i)+ ten .%>Gbp' 'ignal' )an be tran'mitted on one (iber5

produ)ing a 'y'tem )apa)ity o( % Gbp'. T+i' *a-elengt+>paralleli'm )ir)um-ent' t+e problem o(

typi)al optoele)troni) de-i)e'5 *+i)+ do not +a-e band*idt+' e)eeding a (e* giga+ert< unle''

t+ey are eoti) and epen'i-e. T+e 'peed re/uirement' (or t+e indi-idual optoele)troni)

)omponent' are5 t+ere(ore5 relaed5 e-en t+oug+ a 'igni(i)ant amount o( total (iber band*idt+ i'

'till being utili<ed.

S"&carrier %"ltiple9in#

Anot+er met+od )on)eptually related to 4,M i' 'ub)arrier multipleing 6SCM9. n'tead o(

dire)tly modulating a Ptera+ert< opti)al )arrier *a-e *it+ P1##' Mbp' ba'eband data5 t+e

ba'eband data are impre''ed on a Pgiga+ert< 'ub)arrier *a-e t+at i' 'ub'e/uently impre''ed on

t+e T=< opti)al )arrier. 3igure $ illu'trate' t+e 'ituation in *+i)+ ea)+ )+annel i' lo)ated at a

di((erent 'ub)arrier (re/uen)y5 t+ereby o))upying a di((erent portion o( t+e 'pe)trum 'urrounding

t+e opti)al )arrier. SCM i' 'imilar to )ommer)ial radio5 in *+i)+ many 'tation' are pla)ed at

di((erent R3 6Radio 3re/uen)y9 'u)+ t+at a radio re)ei-er )an tune it' (ilter to t+e appropriate

'ub)arrier R3. T+e multipleing and demultipleing o( t+e SCM )+annel' i' a))ompli'+ed

ele)troni)ally5 not opti)ally. T+e ob-iou' ad-antage o( )o't>)on')iou' u'er' i' t+at 'e-eral)+annel' )an '+are t+e 'ame epen'i-e opti)al )omponent'Q ele)tri)al )omponent' are typi)ally

le'' epen'i-e t+an opti)al one'. Fu't a' *it+ T,M5 SCM i'limited in maimum 'ub)arrier

(re/uen)ie' and data rate' by t+e a-ailable band*idt+ o( t+e ele)tri)al and opti)al )omponent'.



T+ere(ore5 SCM mu't be u'ed in )onjun)tion *it+ 4,M i( *e *ant to utili<e any 'igni(i)ant

(ra)tion o( t+e (iber band*idt+5 but it )an be u'ed e((e)ti-ely (or lo*er>'peed5 lo*er>)o't

multiu'er 'y'tem'.

OBSERATION)-Compare t+e SCM and 4,M ')+eme' u'ed in t+e trainer and 'tate in *+at )ir)um'tan)e' you

pre(er ea)+

RESULT)-

Optical Communication File

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