Out here in Manitoba we use unheated/no-electricity OSP fiber patch panel pedestals in some locations, those work without issue down to the occasional -40. Note that that’s using all high-quality components.
For Fletcher’s case, it’s also possible that:
-there had been water intrusion in a splice case or cable on the way – but then that tends to cause complete failure, either on the first occasion or not long after, and not repeating temperature-dependent fade.
-there’s a bad fusion splice on the way whose characteristics are affected by temperature.
My first step in such a case would be to OTDR the line (renting an OTDR if we were a company that didn’t own one) to see approximately where the issue is and to get an idea what kind of issue it is – Fletcher, I guess that your company did not do so at that time?
From: NANOG [mailto:nanog-bounces@nanog.org] On Behalf Of Mel Beckman
Sent: Thursday, January 31, 2019 12:26 PM
To: Fletcher Kittredge <fkittred@gwi.net>
Cc: North American Network Operators' Group <nanog@nanog.org>
Subject: Re: Effects of Cold Front on Internet Infrastructure - U.S. Midwest
Fletcher,
I don’t think that’s true. I find no specs on fiber dB loss being a function of ambient temperature. I do find fiber optic application data sheets for extreme temperature applications of -500F and +500F (spacecraft). You’d think if temperature affected fiber transmission characteristics, they’d see it in space.
What you likely were seeing was connector loss, owing either to improper installation, incorrect materials, or unheated regen enclosures.
Insertion loss (IL) failures, for instance, in the cold are a direct result of cable termination component shrinkage. That’s why regen and patch enclosures need to be heated as well as cooled.
All fiber termination components have stated temperature limits. As temperatures approach -40F, the thermoplastic components in a cable's breakout, jacketing, and fiber fanout sections shrink more than the optical glass. Ruggedized connectors help somewhat, but the rule is that you can’t let optical connectors and assemblies get really cold (or really hot).
A typical spec for a single-mode OSP connector is:
Operating -30C (-22F) to +60C (+140F)
The range for the corresponding Single Mode fiber is:
Operating -55C (-67F) to +70C (+158F)
Storage -60C (-76F) to +70C (+158F)
Installation -30C (-22F) to +50C (+122F)
All professional outside plant engineers know these requirements. So if you’re seeing failures, somebody is breaking a rule.
-mel