I have recently seen a few pictures of optical fibre connectors taken by a microscope after those connectors had been cleaned. The picture states, that the connector fails IEC 61300-3-35 norm. Like theese two bellow:

Example 1

Example 2

But the network with theese connectors is up and running without any problems and it was running ok even before cleaning the connectors. The installation is cca 10 years old. My question is: when is the right time to re-weld optical pigtails, are theese pictures really alarming or we can wait another year without any new pigtail's welding?

  • 2
    Are you seeing any errors on the interface? Even as few as 1 in 10^8 will reduce your throughput.
    – Ron Trunk
    Apr 4, 2016 at 12:15
  • @RonTrunk I am really no expert in optical fibre networks, I am rather a network admin. Those pictures were made by an external company. From the functional point of view I do not see any failures, like ping timeout or something similar. But we have had very strange problems rather undetectable last year that were later fixed by replacing switch and some fiber maintenance, but could have been caused by this problem. Apr 4, 2016 at 13:11
  • 1
    OK, so as a network admin, do you see errors on the interface(s) that use the fiber? I understand thing will "generally work," but even few frame errors will reduce your throughput significantly.
    – Ron Trunk
    Apr 4, 2016 at 13:15
  • 3
    Collisions and late collisions generally indicate a duplex mismatch. But with no CRC errors, I think you are not seeing any degradation due to the fiber.
    – Ron Trunk
    Apr 4, 2016 at 13:39
  • 1
    @RonTrunk Yes duplex mismatch could be the reason, one device is half-duplex, thanks! Apr 4, 2016 at 13:40

2 Answers 2


Check for FCS errors on both switch ports. If there are none for more than a day there's no need to worry at all.

  • Yes, with good media convertors the lines work mostly OK so far. We needed to replace one convertor since then and one line went completely down and needs replacement. We will order re-welding anyway. Aug 14, 2017 at 5:05

if you can, measure whether you have any layer 4 erros i.e run iperf3 UDP test between two hosts on this link. if you do not encounter any loss or too many retransmissions (in TCP test) you don't have to worry.

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