Robot wraps fiber optic cables around existing power lines

Overall, it’s an interesting project and I hope they can solve all issues for a real deployment.

They don’t mention the length penalty that comes from wrapping around the cable or any impact of loss to fiber itself. Given the helical pattern, I’d imagine that they are adding substantial length to any distance they need to achieve. Generally you have about 20dB of loss before you need an amplifier or a terminal node. A typical number for field installed fiber is 0.25dB/km. So there’s some distance penalty needed here. I’m not clear on how you’d add amplifiers to these routes or if they are simple short hops.

Generally regular SMF-28 has a bend radius of 25mm. This is partially for loss reasons as bends below this radius induce loss and partially because bending fiber below that radius creates micro cracks in the fiber. The micro cracks can spread with time and cause the fiber to break. Given the rather large CTE mismatch between the power cable and the fiber cable, the 2 will expand at different rates with temperature, putting additional stress on the fiber, potentially leading to failure.

It’s possible to have a less bend sensitive fiber but it’s generally used more in specialty applications and not as transmission fiber. So it’ll be more expensive per km.

Along the lines of mechanical failure, it would seem that there would be the potential for abrasion between the power cable and the fiber cable jacket.

Finally, it’s a little unclear how repairs would be made. Doesn’t seem very safe to have to splice the fiber on a live cable like this.

I know it's not really relevant to the meat of the article, but I can't trust any of the numbers listed in the article. They claim that "Just 28 per cent of people living in Africa are internet users and two-thirds of those are located in South Africa."

If we take the population estimates of just 4 countries: Nigeria (206 million), Ethiopia (109 million), South Africa (60 million), and Kenya (47 million) we get 422 million people. 28% of that is 118 million, and 2/3 of that is 79 million. Clearly South Africa can't have 79 million internet users if they only have a population of about 60 million.

One thing I started to worry about and which wasn't addressed is that the technique of wrapping the cable around the power line hinders power line repair or could preclude future applications like this. Can the same robot traverse the same line with the cable already applied? Can a second cable be applied over the first?

Discussion from two days ago: https://news.ycombinator.com/item?id=23825132

The fb engineering page has more info [0] and reddit has quite a few comments from people in the industry about its feasibility [1].

[0]: https://engineering.fb.com/connectivity/aerial-fiber-deploym...

[1]: https://old.reddit.com/r/EngineeringPorn/comments/hrb6xv/rob...

My first through is why is Facebook doing this? Why do they have a division that's developing Robotics?

Promising though. Much of the cost of running cable is having someone mount the cable, drive 30 feet down the road, and mount the cable. Over and Over. If they can slash the cost of last mile, that's big.

Without getting into a lot of detail I don't see this being very useful. First off it only works on wires suspended via pin or post insulators on cross arms. There are plenty of other suspension methods used for MV distribution so good luck accommodating them. Most runs are normally interrupted by strain insulator sets on poles containing switch gear or poles that make sharp turns. It also needs to accommodate a wide variety of insulator designs which have varied over the years. Some are tall and narrow, some are short and mushroom shaped. Some have clamps at the top, some are tied with wire.

Any intervention with the robot also requires a highly trained and certified linesman crew to manipulate the thing on a live conductor with a potential upward of 34.5kV line to line. So if the robot gets stuck or breaks down you need a trained crew to handle it. And how easy is it to repair a broken fiber on a downed power line?

This looks like another solar roadways.

Interesting idea, but I don’t see any mention on how they deal with the power line stretching. As power draw goes up, the electric company pumps more juice, which heats up the cable and in summer months it gets so hot (everyone using A/C), that the wires start to stretch and sag. The fiber would need to deal with that.

The article mentions the main costs with deploying fibre "lie within the construction of new poles and other infrastructure". Is there any reason why fibre can't be strung between existing power poles? They aren't conductive, so you don't need to worry about distances to buildings (i.e. they could be run lower than power lines).

A telco was established in the UK by the National Grid during the 1990s using the high voltage distribution network as the backbone, and wrapping fibre around the neutral conductor. They called it Energis, and it had a great slogan at one point: "dial on the pylon"

IIRC after a while they moved to integrating the fibre bundle in the neutral conductor cable.

We’ve wrapped fiber around ground wire in the past. Though here they’re doing it around the conductor. Also their robot is an advancement and pretty cool. But when I’ve worked in the power industry in the past the guys who had experimented with this stuff wound up really hating it for the difficulties it adds to maintenance and the like. So this may be cool but I wouldn’t be surprised to see it rarely used in actual practice. Strikes me a lot like project loon and all these other things where people are trying invent unnecessary shortcuts. If you really want to get internet to people with a reasonable bandwidth/coverage/and cost trade off start building large towers dotted across the continent and use wireless access, or wait for star link.

I don't see this being used other than by electrical grid operators themselves, there's no way they would let third party telecom companies do this, for grid-reliability and safety reasons.

I've seen some gnarly utility line webs in south america. There's something beautiful about the chaos, like a cyberpunk puzzle box for anyone that wants to get signals from it.

How do they pass the more complex transitions between line sections? I vaguely recall that being a significant limitation of existing line-crawling robots.

It's only 1.5km - 2km, and it looks promising, but I wonder how do they splice it. I was hoping the video would tell, but unfortunately not.