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> 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> 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
  www.microtrench-blades.com
  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> 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> 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> 
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> 
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> wrote:

            Oh, meaning the variance between the two, otherwise identical 
models?



            -----
            Mike Hammett
            Intelligent Computing Solutions

            Midwest Internet Exchange

            The Brothers WISP






--------------------------------------------------------------------

            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

            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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            Zach Underwood (RHCE,RHCSA,RHCT,UACA) 

            My website

            advance-networking.com


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