Gluing Fiber

A lot of people asked for my opinion about a recent news article that talks about a new technology that allows gluing fiber directly to streets. The technology comes from a start-up, Traxyl and involves adhering fiber to the streets or other hard surface using a hard resin coating. The company in early trials says the coating can withstand weather, snowplows and a 50-ton excavator. The company is predicting that the coating ought to be good for ten years.

Until I see this over time in real life I don’t have any way to bless or diss the technology. But I have a long list of concerns that would have to be overcome before I’d recommend using it. I’d love to hear other pros and cons from readers.

Surface Cuts. No matter how tough the coating, the fiber will be broken when there is a surface cut in the street. Shallow surface cuts happen a lot more often than cuts to deeper fiber, and even microtrenched trenched fiber at 6 inches is a lot safer. As an example, on my residential street in the last year there have been two water main breaks and one gas leak that caused the city to cut from curb to curb across the whole road surface. I wouldn’t be shocked in a city of this size (90,000 population) if there aren’t a dozen such road cuts somewhere in the city every day. This makes me wonder of the true useful life on the fiber, because that’s a lot of outages to deal with.

I also worry about smaller road disturbances. Anything that breaks the road surface is going to break the fiber. That could be road heaving, tree roots or potholes. I’d hate to lose my fiber every time a pothole formed under it.

Repaving. Modern roads undergo a natural cycle. After initial paving roads are generally repaved every 10-15 years by laying down a new coat of material on top of the existing road. During the preparation for repaving it’s not unusual to lightly groom the road and perhaps scrape off a little bit of the surface. It seems like this process would first cut the fiber in multiple places and would then bury the fiber under a few inches of fresh macadam. I would think the fiber would have to be replaced since there would be no access to the fiber after repaving.

The repaving process is generally done 2 to 4 times during the life of a street until there’s a need for a full new repaving. In repaving the roadbed is excavated to the substrate and any needed repairs made to the substrate before a full new repaving. This process would fully remove the glued fiber from the street (as it would also remove micro-trenched fiber).

Outage time frames. The vendor says that a cut can be mended by either ungluing and fixing the existing wire or else placing a new fiber patch over the cut. That sounds like something that can be done relatively quickly. My concern comes from the nature of road cuts. It’s not usual for a road cut to be in place for several days when there is a major underground problem with gas or water utilities. That means fiber cuts might go days before they can be repaired. Worse, the process of grading and repaving a road might take the fiber out of service for weeks or longer. Customers on streets undergoing repaving might lose broadband for a long time.

Cost. The vendor recognizes many of these issues. One of their suggestions to mitigate the problems would be to lay a fiber on both sides of a street. I see two problems with that strategy. First, it doubles the cost. They estimate a cost of $15,000 per mile and this becomes less attractive at $30,000 per mile. Further, two fibers don’t fix the problem of repaving. It doesn’t even solve road cuts other than halving the number of households served by a given fiber (each fiber serves one side of the street).

I’m also concerned about lifecycle cost. Buried conduit ought to be good for a century or more, and the fiber in those conduits might need to be replaced every 50 – 60 years. Because of street repaving the gluing technology might require new fiber 5 – 7 times in a century, making this technology significantly more expensive in the long run. Adding in the cost of constantly dealing with fiber cuts (and the customer dissatisfaction that comes with outages), this doesn’t sound customer friendly or cost effective.

The article suggests dealing with the fiber cuts by using some sort of a mesh network that I guess would create multiple local rings. This sounds interesting, but there are no fiber electronics that work that way today. If fiber is laid on both sides of the street, then a cut in one fiber knocks out the people on that side of the street. I can’t envision a PON network that could be done any other way.

These are all concerns that would worry me as a network operator. We bury fiber 3-4 feet underground to avoid all of the issues that worry me about fiber at the surface. To be fair, I can think of numerous applications where this could be beneficial. This might be a great way to lay fiber inside buildings. It might make sense to connect buildings in a campus environment. It would alleviate the issues of bringing fiber through federal park land where it’s hard to get permission to dig. It could be used to bring a second path to a customer that demands redundancy. It might even be a good way to get fiber to upper floors of high-rises where the existing fiber ducts are full. But I have a hard time seeing this as a last mile residential network. I could be proven to be wrong, but for now I’m skeptical.

2 thoughts on “Gluing Fiber

  1. Sounds good for rapid temporary emergency restoration following major storms that take down a lot of poles.
    Otherwise, I agree with your skepticism.

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  2. I agree this sounds like a bad idea. And as for the ‘both sides of the street’ idea, in most cities that won’t get very far (literally), because streets cross repeatedly in a gridlike manner (even if not a strict grid layout) – trying to stay on one side of ‘the’ street will soon run into another intersecting street that it has to cross.

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