Chapter 4 - Optical Fiber Connection

8/17/2019 Chapter 4 - Optical Fiber Connection

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Optical FiberConnectionChapter 4


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Introduction• How to launch optical power into fber and fber to

fber?• Considering NA, core size, reractie inde! profle, power

distribution, etc"

• #h$ %oint the fber?• For long cable runs

• Connecting deices such as a&plifers, pigtails, etc" tofbers

• #h$ it is so i&portant?• One wa$ to control losses in fber optic s$ste&

• '$pe o connectorization• (er&anent ) usion splicing

• 'e&porar$ ) &echanical splicing, connector


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*ource+to+fber coupling

• (ower coupled to the fber &easured in radiance brightness-

• .adiance / power radiated into a unit solid angle per unite&itting surace area


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*ource+to+fber coupling

• A part o a unit sphere0s radius 1- surace which is enclosed b$ the solid angle is used as a&easure o the solid angle in steradian sr-

• 2!a&ple• 1 sphere 3 4

• 156 sphere 3 6

• 157 sphere 3 56


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2!a&ple

• A light source radiates in a cone with the solidangle 8 / 9"4 sr" How large is the illu&inatedsurace at a distance o 1 c&?


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:a&bertian radiance

pattern• .adiance pattern or a:a&bertian sourcewhich &eans thesource is e;uall$ brightwhen iewed ro& an$

direction- and thelateral output o ahighl$ directional laserdiode"


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(ower coupling

calculation


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(ower coupling

calculation• 'he power coupled ro& a surace e&itting :2<into a graded inde! fber or r s < a)


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2!a&ple

• Consider an :2< haing a circular e&itting area oradius => & and a :a&bertian e&ission patternwith 1>9 #5c&6"sr- a!ial radiance at a giendrie current" :et us co&pare the optical powers

coupled into two step inde! fbers, one haing acore radius o 6> & with NA / 9"6 and the otheris >9 & with NA / 9"6"


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Fiber+to+fber %oints


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@echanical

&isalign&ents


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:ateral displace&ent

• :oss due to core center not at the sa&e leel

• er$ critical or single &ode fber

Lateral Offset

Fiber


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Angular displace&ent

• :ight trael within B+7 degree inside the fber• Causes 9"6 d loss or eer$ angle displaced

Angular

Misalignment

Fiber


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:ongitudinal displace&ent

air gap-• :oss due to Fresnel reDection in air gap

• Causes about 9"1B d loss or each air5glass interace

Air Gap

Fiber


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2!a&ple

• 'he end aces o two optical fbers with corereractie indices o 1">9 are perectl$ aligned andhae a s&all gap between the&" I this gap isflled with a gel haing a reractie inde! o 1"=,

let us fnd the optical loss in decibels at this %oint"


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NA &is&atch

• #hen light trael ro& high NA to lower NAfber, it e!perience high loss

Fiber with

higher NA

Fiber

Fiber with

lower NA


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Core size &is&atch

• :oss occurs when light trael ro& larger to s&aller core

Fiber with

larger core

Fiber

Fiber with

smaller core

Bottle -Neck


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2nd surace fnishing

• A poor end surace fnishing cause light toreDect into other that intended direction

Rough surface

Fiber


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Connectorization

principlesCONCENTRICITY ALIGNMENT


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FC connector• Description:

Originated from Japan (NTT)

• Coupling Mechanism

Threaded Tpe

• Usage:

!or "ing#emode $se• Applications:

Te#e%omm$ni%ation "stem

• Advantages:

Lo& Cost ' good performan%e

• Disadvantages:

s$a## preterminated* nots$ita+#e for ,e#d termination


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*C connector• Description:

-e.e#op + NTT (Japan)

• Coupling Mechanism

"pring %#ip/ 0$sh and 0$##/

• Usage:

!or 1oth M$#timode and"ing#emode

• Application:

-ata Comm$ni%ation 'Te#e%omm$ni%ation

• Advantages:

More sta+#e and re#ia+#e design/

Internationa# 0remises Ca+#ing"tandard

• Disadvantages:

2igher %ost (than "T)


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*@A connector• Description:Originated from %oa3%onne%tor design* one of theear#iest ,+er opti% %onne%tor

• Coupling Mechanismn4eed* ThreadedTpe

• Usage:

!or M$#timode $se• Application:

Contro#* Monitoring "stem '-ata %omm$ni%ation "stem

• Advantages:0op$#ar in E$rope (-ata%omE5$ipments)

• Disadvantages:6aria+#e #oss d$e to freerotate


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*' Connector• Description:-e.e#op + AT'T in 789:

• Coupling Mechanism"pring #oaded/ 0$sh andT$rn/ ;eed +aoneta%tion/

• Usage:

Main# !or M$#timode $se*"ing#emode .ersion a#soa.ai#a+#e

• Application:-ata Comm$ni%ation

• Advantages:Lo&er %ost* pop$#ar $sagein -ata%om

• Disadvantages:"pring #oaded %a$sesinsta+i#it


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2+6999 '@ connector• Description:

-e.e#op + -iamond• Coupling Mechanism:

"pring %#ip/ 0$sh and 0$##/• Usage:

!or +oth sing#emode andm$#timode $se

• Application:-ata Comm$ni%ation

• Advantages:Lo&er %ost* pop$#ar $sage in

-ata%om• Disadvantages:

-$st %ap %an sometime am


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F%$#t toterminate


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CONNECTORSSPEC!CATONS

• Insertion Loss

'$pical3 9"=d or @ulti&ode

9"6d or *ingle&ode

• Return Loss

'$pical3 +4>d or (C

+>>d or A(C• Operating Temperature/Cycling

'$pical3 +49 to 79 degree @a! change39"=d-

• Repeataility

'$pical3 199 reconnect 9"=d-

•

Tensile !trength49 pounds Eelar-

6 pounds buer-


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Co&ponent o connector• Strain Relie"

:i&iting the bending at the bacGo the connector and secure theconnector to the cable

• #od$%&ousing

@etal or (lastic (art o the

connector that proidescoupling5attach&ent &echanis&(ush+(ull, a$onet or screwthread-

• !errule

@etal5cera&ic5zirconia5plasticprecision part o the connector

that proides a narrow hole16>- or aligning andconcentrate the fber in theconnector"

Kelar

!leee

!train

Relief

Boot

Bo"#$

%ousing

Ferrule

&ust

'oer


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Cable asse&blies

!T"!T !imple# !C"!C !imple# LC"LC !imple#

!C"!C Duple# $DDI"$DDI MTR%"MTR%!imple#


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#hat is a Fusion splicing?

A usion splice is a %unction o two or &ore-optical fbers that hae been &elted together"

'his is acco&plished with a &achine that

peror&s two basic unctions3 aligning o thefbers and &elting the& together t$picall$using an electric arc"


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Example of Fusion Splicing


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How to &aGe a

Fusion splice?Fusion splicing consists o our basic steps, regardlesso how sophisticated a &achine is"

*tep 1 + (repare the fber*tep 6 + Cleae the fber*tep = + Fuse the fber*tep 4 + (rotect the fber


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How to &aGe a

Fusion splice?(reparing the fber is acco&plished b$ stripping awa$all the protectie coatings, %acGets, tubes, etc", until$ou are let with the bare fber" 'he &ain concern hereis cleanliness" A clean fber is essential or the all

i&portant cleaing step"Cleaing the fber properl$ is the Ge$ to successulsplicing" It is irtuall$ i&possible to &aGe a goodusion splice with a poor cleae" A co&parison o twocleaes shows wh$3


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(rocess o usion splicing


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#hat happens i we splice

>9 & to 6"> & fber?#hen trans&itting ro& the 6"> & fber to the >9& fber $ou will e!perience a one+ti&e loss oappro!i&atel$ ="9 d strictl$ due to the dierences incore dia&eter, nu&erical aperture, and scatteringcoeJcient"

'he splice ;ualit$ could also slightl$ aect the totalloss" 'he analog$ o two pipes with dierent innerdia&eters &a$ help isualize that light KleaGsK when

passing ro& the large pipe to s&all pipe, butnegligible KleaGsK occur when water Dows in theopposite direction" #hen trans&itting ro& the >9"9& fber to the 6"> & fber $ou can e!pect onl$ theloss associated with the splice itsel"


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#hat happens i we splice

single+&ode to &ulti&odefber?

'his is t$picall$ not done" *ince the core sizesand glass structure are signifcantl$ dierent,

it is er$ diJcult to obtain a good splice" 2eni a good splice were &ade, a one+ti&e loss o 19 d would occur due to the &is&atchedcores"


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2niron&ental actorsthat aect a splice"

Cold and hot temperatures can be co&pensated orb$ increasing or decreasing the usion current"

&umidit$ does not generall$ aect single+&odesplicing"

&umidit$ does aect &ulti&ode splicing" .educe thecurrent i necessar$"

&umidit$ can aect the cleanliness o the electrodesso checG the& &ore oten than usual in hu&id

conditions"*plicing at high altitudes =,999 t- re;uires a higherusion current"

.e&e&ber, &ost 'atteries e!perience decreased liein cold areas"

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Chapter 4 - Optical Fiber Connection