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> On Behalf Of Chuck McCown via AF
Sent: Wednesday, January 24, 2024 11:12 AM
To: AnimalFarm Microwave Users Group <af@af.afmug.com>
Cc: 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&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?


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<https://www.youtube.com/channel/UCXSdfxQv7SpoRQYNyLwntZg>
________________________________
From: "Zach Underwood" <zunder1...@gmail.com<mailto:zunder1...@gmail.com>>
To: "AnimalFarm Microwave Users Group" <af@af.afmug.com<mailto:af@af.afmug.com>>
Sent: Tuesday, January 23, 2024 12:51:39 PM
Subject: [AFMUG] optical TX power levels
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.

Has anyone seen much difference between optic like this? My sample size is 
small due to the optices costing $4k each

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