Will fiber connections with a lot of DB los cause hardware failures on MS Switches?

[JordanCN]

We have a location where the fiber connections are showing higher than recommended DB losses.  I did not get the measurements back yet so I don't have the exact numbers.  We are not fiber experts so we had someone come in to clean up the fiber ends, re-terminate them if needed, and test the fiber.

The tech said a couple of things that I found odd. He said:

1. If we have excessive loss on the fiber, that could cause fans to fail and the switch to overheat and get physically damaged. I could understand the connection being poor or erratic or even going down, but never thought it could damage the switch physically.
   
   
2. When we connect 4 switches by fiber in sequence like - Switch1 <-> Switch2 <-> Switch3 <-> Switch4, he said it does not matter that the connections between switches are in spec.  If the distance between Switch1 to Switch4 is greater than a specifications, then we will have issues.  That sounded odd to me as well.

Does this sound right, or should I be looking for another fiber tech?

[Mloraditch · Accepted solution]

1. I know there is a heat factor to generating the laser so I can see #1 theoretically being true but I've never heard of that. I mean in theory an SFP with an offline fiber would be seeing horrible loss and running at its highest possible output to try to work and that doesn't break things. Perhaps this is an old school thing or something for very high end/output/industrial optics in things like submarine cables or something??

2. The net effect is correct in that if the middle switches in a sequence are  having issues then of course the outer edges of the sequence would have issues talking to each other, but if say #1 was true that would not cause the SW1 to SW2 to also have that issue. The distance only matters between the two connecting devices in regular gear. Again there could be some application where this matters, but not in any application I've ever seen Meraki and similar gear used for.

Honestly they sound like either being very old school and there are things that used to happen that don't anymore or similar to my other comment, they generally work in very different environments. I don't require my fiber cabling techs to understand SFPs or switches and just want them to run cables correctly, so as to dumping them or not just depends on what all they are actually doing and if the work is quality.

[JordanCN]

Thanks Mioraditch, 

I thought the same.  Plus, I would imagine I would have been getting warnings from the Meraki dashboard of excessive heat, excessive packet loss, or high fan speed if that were the case.

Actually, that would be a nice addition to the dashboard if they could put the current temps and fan speeds on the switch details instead of just getting alerts when they exceed.

[cmr]

@JordanCN have you looked at what the DOM data on the switch port says?   It should tell you if the transceiver is either not receiving enough light, or is having to use too much power to send a signal.