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The specifications of this optical usb cable specify operating conditions of more than 0 °C. What is the physical reason behind this?

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    \$\begingroup\$ "Degree" is a unit for angles. If you mean temperature you have to add C or F. \$\endgroup\$ – Curd Mar 6 '17 at 11:57
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What is the physical reason behind this?

Probably, there's no specific physical reason for exactly this range.

It simply costs significant money to test electronics, and 0 °C – 45 °C is a common range for consumer electronics certifications. If you're an industrial customer of Corning, I'm sure they'll be willing to offer devices certified for a larger temperature range, of course, for a price.

But think about it: What USB equipment exactly do you have that is specified to work below 0 °C? I've yet to encounter one consumer device that has that certification. Hence, it's very unlikely a user of the cables would ever be able to complain about the temperature range – simply because the printer/hard drive/SSD/camera that he'll be using with it isn't certified for freezing temperatures, either.

If there are physical reasons, they'd be:

  • electrolytic capacitors not being happy about freezing
  • voltage converters used to power the internal electronics changing reference voltages, leading to malfunction
  • laser diodes might not work great with reduced carrier mobility
  • mechanical properties of the rubber/silicone tubing, plastic case making it e.g. more brittle
  • increased chance of condensation/thaw on the device

The optical properties of the fiber optics almost certainly have nothing to do with it.

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  • \$\begingroup\$ RE: consumer devices that operate below 0 C; Anything meant for use in your car (like the radio, nav system, etc) should be designed to operate below 0 C. Having to get a car started at or below 0 C is pretty common in many places. \$\endgroup\$ – The Photon Mar 6 '17 at 16:39
  • \$\begingroup\$ And car manufacturers buying cabling for internal connections are exactly those that will not buy consumer-grade USB3 adapter cables, but insist on extended industrial/automotive-grade qualification :) \$\endgroup\$ – Marcus Müller Mar 6 '17 at 16:46
  • \$\begingroup\$ Yes, that's true. But a car radio or nav unit isn't an unusual thing for a consumer to go and buy as an after-market product. That makes it a "consumer good" to me even if it is likely designed to higher specs than stuff meant for use only in climate control environments. \$\endgroup\$ – The Photon Mar 6 '17 at 16:48
  • \$\begingroup\$ So, yeah, you're right, but then again, if the consumer goes out and buys a third-party car nav, chances are it's not even rated for operation below 0 °C, even though it would make sense to have that. But you're right, the whole car aftermarket is kind of a grey zone between automotive-grade electronics and consumer-grade electronics. \$\endgroup\$ – Marcus Müller Mar 6 '17 at 16:50
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The short answer is that they didn't test them at lower temperatures.

The longer answer as to why many things aren't qualified to work at low temperatures is icing. If the thing isn't sealed (and I don't see an IP67 rating) then water from the atmosphere may freeze onto it at low temperature, shorting out the PCB in places.

There are also issues with temperature compensation - lots of oscillators, semiconductors and resistors change behaviour with temperature.

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Presumably the optical to electrical conversion components are only rated to 0C - 45C. Read the spec. properly.

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  • \$\begingroup\$ In what way does reading this spec properly yield any additional information? Wouldn't one of the other reasons listed in this answer be a more likely explanation for a high volume, (relatively) low priced consumer product rating? \$\endgroup\$ – uhoh Mar 12 '17 at 13:20
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Why can optical usb cables not operate below 0°C?

it says its operating temperature is from 0 to xc. it didn't say that the cables will not operate below 0c.

two different things.

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  • \$\begingroup\$ Can you explain the difference? \$\endgroup\$ – Bort Mar 6 '17 at 13:16
  • \$\begingroup\$ It is guaranteed to operate correctly at temperatures down to 0 C. It is not guaranteed to fail at -1 C. \$\endgroup\$ – Peter Bennett Mar 6 '17 at 17:02
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If you mean 0 degrees celsius, it's probably because ice may damage the cable. That cable is not meant to be used in freezing temperatures - simple as that.

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