FW: FW: OTDR Launch Cable/Receive Cable Length for Singlemode

[Tim Glass]

 

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From: Bill.Pa...@corning.com [mailto:Bill.Pa...@corning.com]
Sent: Friday, April 11, 2008 8:52 AM
To: Tim Glass
Cc: Robert...@corning.com
Subject: Re: FW: OTDR Launch Cable/Receive Cable Length for Singlemode

Tim,

Thanks for the question.  You need at least 1km launch for SM OTDR testing to be able to read past the dead zone that is inherent to all OTDRs and to provide the most accurate reading possible.  If you use a shorter launch, you will not likely get an accurate reading on the first connector, though you will get a visible trace and will likely have good results on later events.  That's the layman's answer.  Let me know if you need the technical one and I'll send to Engineering Services to respond.

Bill

Tim Glass <tcg...@weic.com> 04/11/2008 06:51 AM

To bill.pa...@corning.com cc Subject FW: OTDR Launch Cable/Receive Cable Length for Singlemode

 
Bill,
Your input?
Tim
-----Original Message-----
From: fiber-...@googlegroups.com [mailto:fiber-...@googlegroups.com]
On Behalf Of rjhintz
Sent: Thursday, April 10, 2008 4:40 PM
To: Fiber Optics
Subject: OTDR Launch Cable/Receive Cable Length for Singlemode


Since you guys are so helpful, let me ask another OTDR launch cable question
that I asked over in comp.dcom.cabling, but is being ignored among the spam.

The JDSU Fiber Optic Test Reference Guide,
http://lw.pennnet.com/whitepapers/wp.cfm?id=665,
says a launch cable used for singlemode should be 1km to 2km long.

Is that what's used in practice?  What's the consequence of not using a
launch cable that long (besides the generic answer of unreliable readings,
which would make sense.) Thanks.