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


On Jan 30, 2019, at 3:05 PM, Fletcher Kittredge <fkittred@gwi.net> wrote:


Cold changes the transmission characteristics of fiber. At one point we were renting some old dark fiber from the local telephone company in northern Maine. When it would get below -15%-degree F the dB would get bad enough that the link using that fiber would stop working. The telephone company was selling us dark fiber because regulation required them to. They refused to give us another fiber nor inspect/repair. They took the position they were required to sell us fiber, not working fiber.


On Wed, Jan 30, 2019 at 11:41 AM Mark Tinka <mark.tinka@seacom.mu> wrote:
For anyone running IP networks in the Midwest, are you having to do anything special to keep your networks up?

For the data centres, is this cold front a chance to reduce air conditioning costs, or is it actually straining the infrastructure?

I'm curious, from a +27-degree C summer's day here in Johannesburg.

Mark.


--
Fletcher Kittredge
GWI
207-602-1134