Yeah, I was gonna say, the OTDR might give you a perfect fiber distance, but accounting for the built-in twist and the slack loops complicates matters.
From: AF <af-boun...@af.afmug.com> On Behalf Of ch...@go-mtc.com Sent: Tuesday, August 27, 2024 3:47 PM To: AnimalFarm Microwave Users Group <af@af.afmug.com> Subject: Re: [AFMUG] fiber patch cables Wow, sometimes looking for gopher damager over 20 miles I have been off a mile. From: Josh Luthman Sent: Tuesday, August 27, 2024 1:30 PM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] fiber patch cables So far every time we've used the OTDR it's been accurate within 1 foot. On Tue, Aug 27, 2024 at 12:55 PM Trey Scarborough <t...@3dsc.co <mailto:t...@3dsc.co> > wrote: 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 mailto:af-boun...@af.afmug.com On Behalf Of Josh Luthman Sent: Monday, August 26, 2024 4:20 PM To: AnimalFarm Microwave Users Group mailto:af@af.afmug.com 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 <ch...@go-mtc.com <mailto:ch...@go-mtc.com> > 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 <t...@voltbb.com <mailto:t...@voltbb.com> > 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 <khoh...@kwom.com <mailto:khoh...@kwom.com> > 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. -- AF mailing list AF@af.afmug.com <mailto:AF@af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com <mailto:AF@af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com _____ -- AF mailing list AF@af.afmug.com <mailto:AF@af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com <mailto:AF@af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com <mailto:AF@af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com _____ -- AF mailing list AF@af.afmug.com <mailto:AF@af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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