Hey Josh, What cheap Chinese OTDRs are you using? I'm in the market.
On Tue, Aug 27, 2024 at 2:31 PM Josh Luthman <j...@imaginenetworksllc.com> wrote: > 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> 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 <af-boun...@af.afmug.com> <af-boun...@af.afmug.com> *On >> Behalf Of *Josh Luthman >> *Sent:* Monday, August 26, 2024 4:20 PM >> *To:* AnimalFarm Microwave Users Group <af@af.afmug.com> >> <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> 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> 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> 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 >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> -- >> AF mailing list >> AF@af.afmug.com >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> ------------------------------ >> >> -- >> AF mailing list >> AF@af.afmug.com >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> -- >> AF mailing list >> AF@af.afmug.com >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> >> >> -- >> AF mailing list >> AF@af.afmug.com >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com > -- Carl Peterson *PORT NETWORKS* 401 E Pratt St, Ste 2553 Baltimore, MD 21202 (410) 637-3707
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