optical time domain refelecto meter.ppt

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Optical Time Domain

Refectometer

1



OutlinesWhat is OTDR?

Basic principle o operation.

Basic requirements or setup o OTDR. Types o OTDRs available.

Testing using OTDR

Trace nalysis

!imitations

"



What is OTDR?OTDR #Optical Time Domain Refectometer$ is a

versatile portable instrument that is use% &i%ely toevaluate the characteristics o an installe% 'ber optic

lin(.

)t also measures optical 'ber parameters such asattenuation* length* optical connector an% splices loss.

OTDR technology is %esigne% to provi%e a singleen%e% test o any cable.

OTDR un%amentally is an Optical RDR.

+



Basic operational principle

OTDR !,-R

,ignalprocessor an%

%isplayhoto%etector

/iber un%er test

Return,ignals

Optical0irculator

)nputsignal



OTDR ,etup

2



OTDR ,etup3 R45- The 'rst one to consi%er is 6Range7 or %istance o 'ber to test.

8any OTDRs have automatic length %etection unctions* but i

the length is (no&n* the user can set the range manually. The

range setting shoul% be a%9uste% to no less than 1.2 to ": the

'ber span un%er test.

;



Range<.

=



OTDR ,etup3 ulse Wi%th

!onger pulse &i%ths are use% or longer range tests. s %istance

increases* pulse &i%th must go up* other&ise traces &ill appear

6noisy7 an% rough.

,imilarly* short traces &ill be inconclusive i long pulse &i%ths are

use% #events may be misse% or clippe%$.>



ulse Wi%th<



OTDR ,etup3 )n%e: o

Reraction )n revie&* the )n%e: o Reraction is a &ay o measuring the

spee% o light in a material. !ight travels astest in a

vacuum* such as outer space. The actual spee% o light in a

vacuum is +@@*@@@ (ilometers per secon%* or 1>;*@@@ milesper secon%. )n%e: o Reraction is calculate% by %ivi%ing the

spee% o light in a vacuum by the spee% o light in some

other me%ium.

Index of Refraction = Speed of Light in a Vacuum

Speed of Light in a Medium

1@



)n%e: o Reraction<) the 5roup )n%e: o Reraction #5)R$ setting in the OTDR

%oes not match that o the 'ber un%er test* the results &ill

sho& incorrect %istances as a result.

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OTDR ,etup3 veraging

Timeveraging time reers to ho& long the user allo&s the %evice to

ta(e samples #ho& long the test 6runs7$. The longer the

testingAaveraging time allo&e%* the better the result.

-ventually* enough %ata is average% or a goo% test an%

continuing to test &ont yiel% any more o an accurate result.

1"



OTDR ,etup3 veraging

Time<

1+



OTDR Types

8ost common OTDRs use a 6console7 %esign allo&ing the user to

upgra%e or s&ap bet&een 88 an% ,8 mo%ules.

These oCer similar analytical eatures to the lab quality OTDRs* but

are more rugge% an% 'el% portable. /iles can be save% to various

me%ia an% later %o&nloa%e% to a 0. 1



8icro OTDRs

8icro3OTDRs are the ne:t generation o ast* economical test sets

or 'el% use. These mo%els oCer e&er eatures than the larger

console %esign an% are currently not upgra%eable. 12



OTDR Testing

5enerates a baseline trace 6visual7 o the

lin(.

0an i%entiy an% evaluate speci'c events in

the lin(.

0able acceptance tool.

/ault location tool.

-:cellent %ocumentation capabilities.

1;



Troubleshooting Tools

Ese%

1=



OTDR Trace nalysis

0onnect the OTDR to a launch #suppressionAreerence$ cable.

The secon%ary en% o the launch cable &ill be connecte% to

an access panel at one en% o the 'ber optic span un%er test.

Optionally* a receive cable can be attache% at the ar en%. 1>



Observations on %isplay

1



Trace nalysis<.

"@



Trace nalysis<.8ost commonly* users manipulate t&o cursors* 67 an% 6B7*to illustrate &hat is reerre% to as 6t&o point loss7 on an

OTDR result.

This can be use% to sho& loss in a single event or in a

group o events. These cursors can be in%ivi%ually move%

let an% right to speci'c points on the result.

"1



Trace nalysis<.

Ese cursorAmar(ers to isolate in%ivi%ual events* such as the

repair splice location #above$<

""



Trace nalysis<.

<or the t&o point loss #attenuation$ o an entire net&or(

span #above$< "+



Trace nalysis<.

<or the physical length o a 'ber span #above$.

"



OTDR !imitations The limite% %istance resolution o the OTDR ma(es it very

har% to use in a !4 or buil%ing environment &here cables

are usually only a e& hun%re% meters long.

The OTDR has a great %eal o %iFculty resolving eatures in

the short cables o a !4 an% is li(ely to sho& GghostsG rom

refections at connectors* &hich conuses the user.

"2



RerencesOptical /iber 0ommunications3 Iohn 8. ,enior

Optical /iber 0ommunication3 5er% Jeiser

httpAA&&&.lanshac(.comA'ber3optic3tutorial3

testing.asp:

&&&.'berne:t.com

httpAA&&&.9imhayes.comAOTDRAot%rsKc.htm

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optical time domain refelecto meter.ppt