“ Fiber optic cable weights 752 kilograms (1757 lbs) per kilometer”
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What is used for these devices is certainly not the robust multithread fiber optic cable we use domestically. Such cables are designed for long term use and have all sorts of “armor” and moisture protections built in. It would only make sense to use light weight single tube thread only suitable for a single mission. In other words I suspect it would be even more “expendable” than the drone it serves.
Yes, I’m sure almost the entire mass of direct-burial fiber optic is sheathing.
One reference says typical weight of 1000 feet could be ten to twenty pounds.
The actual fibers are much smaller than what you see along the road being buried. Surprised the other guy didn’t know that.