The only thing you have to worry about with shorter cables is the
reflection. In some instances with dirty connector at just the right
connector you can get reflection back in to the transmitter that can
cause errors, the tx to shut down or premature failure. This is very
uncommon with LR 10G and less optics and can be prevented from making
sure you have clean connectors. Check the RX and TX levels and make sure
you don't have excessive loss. With 100G its a little different story
due to the combined power of multiple channels, but still can be
prevented by cleaning connectors, but in some instances Ive had to use
attenuation when mixing different vendor optics.
The using no launch on an OTDR most automatically calibrating OTDRs will
work without one. Your results can be off though. Most of the lower cost
ones are also lower powered and have less of an RX sensitivity so they
don't suffer as much from the reflections interfering when testing. I
can test all day long with my little otdrs without one, but my long
range 200k+ units I have to have a minimum of a 1k spool on it or you
see ghosts. They will show up as repeating events at even intervals. Not
something you will see on shorter runs either.
On 8/26/24 4:31 PM, Ken Hohhof wrote:
I should note that apparently I used to do this with direct attach
cables (DAC) but I think that was a pain, one more thing to stock and
to bring with for projects. Whereas I’d always have boxes full of
SFPs and fiber patch cords.
*From:*AF <[email protected]> *On Behalf Of *Josh Luthman
*Sent:* Monday, August 26, 2024 4:20 PM
*To:* AnimalFarm Microwave Users Group <[email protected]>
*Subject:* Re: [AFMUG] fiber patch cables
People say you need a launch cable but our cheap china OTDRs have no
issues seeing the connector at the end of the patch cable and stuff
beyond. I bought a big launch cable back in the day and never use it
anymore.
Might be different with AE?
On Mon, Aug 26, 2024 at 5:16 PM <[email protected]
<mailto:[email protected]>> wrote:
Only minimum length I know of is the OTDR dead zone. If that is a
problem you purposely lengthen the cable with a launch cable.
*From:*Josh Luthman
*Sent:*Monday, August 26, 2024 1:59 PM
*To:*AnimalFarm Microwave Users Group
*Subject:*Re: [AFMUG] fiber patch cables
Reddit is wrong. Gasp.
Connectors are loss, there is more loss in either one of the
connectors than there is the single mode glass.
Between a switch/router in a rack what I see all the time is long
(like 5/10/15 feet) cables and then put the slack in a loop along
the posts.
On Mon, Aug 26, 2024 at 1:19 PM TJ Trout <[email protected]
<mailto:[email protected]>> wrote:
Patchbox makes some great products, their fiber system is
pretty slick but expensive.
Cable length is irrelevant it's optical budget / Rx signal
strength. Normally on 2-20k LR optics you are ok with any
length cable, 40km+ needs a pad on short spans. (Attenuator)
On Mon, Aug 26, 2024, 8:29 AM Ken Hohhof <[email protected]
<mailto:[email protected]>> wrote:
Is there a minimum length for a single mode fiber patch cable?
I have been using 1 meter cables and they are almost
always too long, I’m talking about going between routers
and switches in a rack, stuff like that. I see that FS
sells 0.5 meter cables, but I saw somewhere like maybe on
Reddit someone claiming there was a minimum length. Given
SM fiber and LR optics, I don’t see how 0.5 or 1.0 meter
would be different they are both essentially zero length.
Probably there’s some kind of cable tray or cable
management solution I could be using but I’ve never liked
such things.
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