Out of curiosity, what did the provider tell you about this trace? The -20 and -15 reflectance stand out pretty loud and clear. If their OTDR has a “smart” mode it would have flagged those as failures. If they didn’t see a problem here they might need a test device smarter than they are.
From: AF <af-boun...@af.afmug.com> On Behalf Of Zach Underwood Sent: Thursday, January 25, 2024 10:26 AM To: AnimalFarm Microwave Users Group <af@af.afmug.com> Subject: Re: [AFMUG] optical TX power levels wow thanks for the detail, I will work with the boss and the fiber provider to try to address some of those problems. On Thu, Jan 25, 2024 at 10:14 AM <dmmoff...@gmail.com <mailto:dmmoff...@gmail.com> > wrote: As an OTDR trace it looks really good, but your problem might be at event 18 and/or 19. I don’t know how much you wanted to know so I apologize if I’m starting too far towards the beginning. #18 is around 100m from the end and has reflectance of -21.36. That’s crappy. The -15 below it is even crappier. A UPC connector should be -40 to -50 dB An APC connector should be better than -55 or -60 depending on who you believe. If the distance is correct then maybe #18 is a cross connect panel? #19 should be your Arista. Start with re-cleaning those connectors. One-click cleaners are fast and cheap. They only shot this in one direction, so we don’t know about the connectors on the other end. I’d clean it on both sides. The line graph is showing you attenuation over distance. You’re averaging under 0.2dB per Km so that’s really good. The table below is showing you 19 events. An event is any point along the graph where attenuation suddenly increased. Events are either “reflective” or “non-reflective”. In the first column of the table they’re showing you a /R or /N for reflective or non-reflective. You can also tell that in the line graph because reflective events will have a spike before the dip. You don’t want reflections. Reflections are given in a -dB and you want it farther from zero (i.e.: -55 reflectance is better than -40 reflectance). (And side comment: reflectance is the same thing as return loss, but in optics people seem to prefer the term “reflectance”. The only difference is return loss should be indicated with a positive number and reflectance is negative. Return Loss = 10*log(incident power/reflected power) in +dB Reflectance = 10*log(reflected power/incident power) in -dB ) Non-reflective events are things adding attenuation but not adding reflectance. Those would be fusion splices, coils, and bends. Reflective events mean there’s an exposed face of glass. Those would be mechanical splices or connectors. Reflective events could also be a fault in the fiber like a bubbled fusion splice. All that noise at the end of the line shows where the dead end is. On that test result the only event I don’t like along the middle of the run is #9. 4dB is a lot for one event. It might be a less than perfect splice, a tight bend in a splice tray, a slack coil that’s too tight, or whatever. It’s not enough to ruin this link, and it’s probably ok if it stays at 4dB forever. There are some underground cases where I’ve seen the same high attenuation events for years, but they’re not hurting us and it’s too much trouble to access the case to fix something that isn’t currently a problem. If nobody ever said this before: you should clean connectors every time they are handled. No matter what anybody tells you, the caps they come with are not “dust caps” and they won’t keep it clean; the caps are there so the glass face doesn’t get scratched. When I’m plugging things in I clean the jack, clean the plug, and then treat it like I’m playing the old Operation game: If the ferrule touches anything before it goes into the hole then it’s “Bzzzzzt!” and reclean it. The dispersion thing is a new concept for me, and I don’t think you could diagnose it from this one trace. From what I’m gathering in this thread, I think you’d have to shoot it on multiple wavelengths and compare the differences. This trace is only at 1550nm. -Adam From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com> > On Behalf Of Zach Underwood Sent: Wednesday, January 24, 2024 7:41 PM To: AnimalFarm Microwave Users Group <af@af.afmug.com <mailto:af@af.afmug.com> > Subject: Re: [AFMUG] optical TX power levels Ok we got the report back from the fiber supplier. This is new to me so anyone can offer insight into it? PDF https://drive.google.com/file/d/1KeIuWHFsiKZHxcmpPiY8PX_-PABl55Sz/view?usp=sharing On Wed, Jan 24, 2024 at 6:00 PM Daniel Pautz via AF <af@af.afmug.com <mailto:af@af.afmug.com> > wrote: Dispersion compensation module - https://www.fs.com/products/65783.html From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com> > On Behalf Of Ken Hohhof Sent: Wednesday, January 24, 2024 3:53 PM To: 'AnimalFarm Microwave Users Group' <af@af.afmug.com <mailto:af@af.afmug.com> > Subject: Re: [AFMUG] optical TX power levels I spent a few minutes searching on the term DCM and came up with “chirped fiber Bragg grating”. https://en.wikipedia.org/wiki/Fiber_Bragg_grating OK, I’m out of my depth now. From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com> > On Behalf Of Daniel Pautz via AF Sent: Wednesday, January 24, 2024 4:40 PM To: AnimalFarm Microwave Users Group <af@af.afmug.com <mailto:af@af.afmug.com> > Cc: Daniel Pautz <d...@webnx.com <mailto:d...@webnx.com> > Subject: Re: [AFMUG] optical TX power levels Perhaps pick up a used cheap DCM and see if it helps, adjustable preferred if not as close to the fiber distance. Our newest 100G dwdm build (dozen 100G optics) very much needed a DCM on it. From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com> > On Behalf Of Chuck McCown via AF Sent: Wednesday, January 24, 2024 3:36 PM To: 'AnimalFarm Microwave Users Group' <af@af.afmug.com <mailto:af@af.afmug.com> > Cc: ch...@go-mtc.com <mailto:ch...@go-mtc.com> Subject: Re: [AFMUG] optical TX power levels Gotta think of the Fourier series of the pulse. Yes group velocities or group delay of the whole enchalada. It is all kinda the same thing. They were doing some kind of soliton fiber development. Haven’t heard much for some time about that. No idea how frequency pure/coherent the tx is. I imagine phase coherency is a big deal. From: Ken Hohhof Sent: Wednesday, January 24, 2024 4:12 PM To: 'AnimalFarm Microwave Users Group' Subject: Re: [AFMUG] optical TX power levels Looks like different wavelengths have different group velocities, so compensation is possible (but probably not cheap?). Is this because the transmitter doesn’t generate literally a single wavelength? Or is this a WDM issue? Chuck says the pulses get smeared out in time, that sounds like the first one. From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com> > On Behalf Of Chuck McCown via AF Sent: Wednesday, January 24, 2024 3:56 PM To: AnimalFarm Microwave Users Group <af@af.afmug.com <mailto:af@af.afmug.com> > Cc: ch...@go-mtc.com <mailto:ch...@go-mtc.com> Subject: Re: [AFMUG] optical TX power levels Yeah, the pulses tend to get smeared out in time if there is too much dispersion. Similar to trying to use too high level of QAM with SNR issues. From: Josh Luthman Sent: Wednesday, January 24, 2024 12:26 PM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] optical TX power levels Even if the RX level is good? > rx was within 0.3dBm on all 4 lanes on both sides On Wed, Jan 24, 2024 at 1:22 PM Daniel Pautz via AF <af@af.afmug.com <mailto:af@af.afmug.com> > wrote: Yeah makes me think the two paths have different loss. We have had that on mirrored paths, or even single paths with crappy splices on one of the strands. From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com> > On Behalf Of Chuck McCown via AF Sent: Wednesday, January 24, 2024 11:12 AM To: AnimalFarm Microwave Users Group <af@af.afmug.com <mailto:af@af.afmug.com> > Cc: ch...@go-mtc.com <mailto:ch...@go-mtc.com> Subject: Re: [AFMUG] optical TX power levels Did anyone do dispersion testing on the fiber? Chuck McCown McCown Technology Corporation 8401 N Commerce Dr Lake Point, Utah 84074 801-250-9503 435-830-4306 cell www.mccowntech.com <http://www.mccowntech.com> www.microtrench-blades.com <http://www.microtrench-blades.com> www.terabitnetworks.com <http://www.terabitnetworks.com> From: Zach Underwood Sent: Wednesday, January 24, 2024 12:07 PM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] optical TX power levels tired again this morning and still no link. rx was within 0.3dBm on all 4 lanes on both sides. We got 10gb 80km to link up. This will do for now. We will be looking at getting 40gb 80km single lane optics or adding another site to fiber loop to shorten the footage to under 40km. On Wed, Jan 24, 2024 at 11:14 AM Colin Stanners <cstann...@gmail.com <mailto:cstann...@gmail.com> > wrote: So both of those SFPs are within the tx power range. 100G may not work on a link that long unless you have dispersion compensation fiber on the path or in a huge loop in a box style at one end. You likely cannot change tx power levels on those SFPs, they will run at the max they can do for that specific unit. On Wed, Jan 24, 2024, 7:46 a.m. Zach Underwood <zunder1...@gmail.com <mailto:zunder1...@gmail.com> > wrote: TX Power 2~6.5dBm I am struggling to get this 100gb link up. In the field this link is quoted at 31 miles. The rx levels are -22 and -20 on both sides but I can't get it to link. I take the same optics to the lab and add 20dbm of attenuator to get almost the same rx levels as the field and it will link up. I have added error-correction encoding reed-solomon per the user guide for links over 40km. So far I have not found a way to change the TX levels in arista, the options are in the CLI but they dont seem to change the outcome. For me this is the first time dealing with 80km optics or 100gb optics over 10km. switch is Arista DCS-7060SX2-48YC6-R https://resource.fs.com/mall/doc/20230531114903y4ljxw.pdf https://www.fs.com/products/115818.html?attribute=29032 <https://www.fs.com/products/115818.html?attribute=29032&id=3462585> &id=3462585 On Wed, Jan 24, 2024 at 8:35 AM Colin Stanners <cstann...@gmail.com <mailto:cstann...@gmail.com> > wrote: There should be. What does their datasheey indicate for tx power range? On Wed, Jan 24, 2024, 7:31 a.m. Zach Underwood <zunder1...@gmail.com <mailto:zunder1...@gmail.com> > wrote: Yep labels identical but there is a difference in default power levels. On Wed, Jan 24, 2024, 8:13 AM Mike Hammett <af...@ics-il.net <mailto:af...@ics-il.net> > wrote: Oh, meaning the variance between the two, otherwise identical models? ----- Mike Hammett <http://www.ics-il.com/> Intelligent Computing Solutions <https://www.facebook.com/ICSIL> Midwest Internet Exchange The Brothers WISP <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> _____ <https://www.facebook.com/ICSIL> From: "Zach Underwood" <zunder1...@gmail.com> To: "AnimalFarm Microwave Users Group" <af@af.afmug.com> Sent: Tuesday, January 23, 2024 12:51:39 PM Subject: [AFMUG] optical TX power levels <https://www.facebook.com/ICSIL> I got 2x 100gb 80km optics from FS that run difficult default TX power levels one is 3.81dBm and the other 2.63dBm, the config on the arista devices hosting the optics is the same. <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> Has anyone seen much difference between optic like this? My sample size is small due to the optices costing $4k each <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> -- <https://www.facebook.com/ICSIL> Zach Underwood (RHCE,RHCSA,RHCT,UACA) My website <https://www.facebook.com/ICSIL> advance-networking.com <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com <https://www.facebook.com/ICSIL> -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com <https://www.facebook.com/ICSIL> -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> -- <https://www.facebook.com/ICSIL> Zach Underwood (RHCE,RHCSA,RHCT,UACA) My website <https://www.facebook.com/ICSIL> advance-networking.com <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com <https://www.facebook.com/ICSIL> -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> -- <https://www.facebook.com/ICSIL> Zach Underwood (RHCE,RHCSA,RHCT,UACA) My website <https://www.facebook.com/ICSIL> advance-networking.com <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> _____ <https://www.facebook.com/ICSIL> -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com <https://www.facebook.com/ICSIL> -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com <https://www.facebook.com/ICSIL> <https://www.facebook.com/ICSIL> _____ <https://www.facebook.com/ICSIL> -- AF mailing list 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 -- Zach Underwood (RHCE,RHCSA,RHCT,UACA) My website <http://zachunderwood.me> advance-networking.com <http://advance-networking.com> -- AF mailing list AF@af.afmug.com <mailto:AF@af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- Zach Underwood (RHCE,RHCSA,RHCT,UACA) My website <http://zachunderwood.me> advance-networking.com <http://advance-networking.com>
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