OTDR Launch Cable/Receive Cable Length for Singlemode

[rjhintz]

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.

[tcg...@weic.com]

: 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

On Apr 10, 4:39 pm, rjhintz <rjhi...@gmail.com> wrote:
> 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.)

> ThRich,
It really falls into how accurate, they want their tests, here in
Pennsylvania most Engineers require both tests the Tier1 power meters
light source for better accuracy and depending on distances do both
tests with the OTDR for Tier 2 test. I would just qualify in your
scope of work.
Tim