Most people don’t realize the damage done every year to fiber and other wired networks by animals.
Squirrels. These cute rodents are the number one culprit for animal damage to aerial fiber. To a lesser degree, fiber owners report similar damage by rats and mice. Squirrels mainly chew on cables as a way to sharpen their teeth. Squirrel teeth grow up to 8 inches per year, and if squirrels aren’t wearing their teeth down from their diet, they look for other things to chew. There has been speculation that squirrels prefer fiber to other cables due to some oil or compound used in the fiber manufacturing process that attracts them.
Level 3, before they were part of CenturyLink, reported that 17% of their aerial fiber outages were caused by squirrels. A Google search turns up numerous outages caused by squirrels.
Companies use a wide variety of techniques to try to protect from squirrel damage – but anybody that has ever put out a bird feeder knows how persistent they can be. One deterrent is to use hardened cables that are a challenge for squirrels to chew through. However, there have been cases reported where squirrels partially chew through such cables, which still lets in water and can cause future damage.
A more common solution is adding a barrier to keep squirrels away from the cable. There are barrier devices that can be mounted on the pole to block squirrels from moving higher. There are also barriers that are mounted where cables meet a pole to keep the squirrels away from the fiber. There are companies that have tried more exotic solutions, like deploying ultrasonic blasters to drive squirrels away from fiber. In other countries, the fiber providers sometimes deploy poisonous or obnoxious chemicals to keep squirrels away from the fiber. These techniques are frowned upon or illegal in the US.
Gophers. Buried fiber also has a gnawing pest in the pocket gopher. There are thirteen species of pocket gophers that range from 5 to 13 inches in length. The two parts of the country with the most pocket gophers are the Midwest plains and the Southwest. Gophers live on plants and either eat roots or pull plants down through the soil.
Pocket gophers can cause considerable damage to fiber. These rodents will chew almost anything, and there have been reported outages from gophers that chewed through buried gas, water, and electric lines. Gophers typically dig between 6 and 12 inches below the surface and are a particular threat to buried drops.
There are several ways to protect against gophers. The best protection is to bury fiber deep enough to be out of gopher range, but that can add a lot of cost to buried drops. I have a few clients that bore drops rather than trench or vibrate them for this reason. Another protection is to enclose the fiber in a sheathe that is over 3 inches in diameter. A tube of that size is too big for the gophers to bite. Again, this is an expensive solution for buried drops. Another solution is to surround the buried fiber with 6 – 8 inches of gravel of at least 1-inch size – anything smaller gets pushed to the side by gophers.
There are examples of even more exotic animal damage to fiber. Large birds of prey have sharp talons that can create small cuts in the sheathe and allow in water. Flocks of birds repeatedly sitting on a fiber can cause sag and stretching of the fiber. I can remember living in Florida and seeing end-to-end birds sitting on wires – that has to add a lot of weight to a 200-foot fiber between poles. Over the last year I’ve seen several reports of sharks chewing on undersea fibers.
Finally, although not directly animal related, a common cause of rural fiber cuts happens when farmers hit fiber with a backhoe when burying dead livestock. They typically bury wherever an animal died, including in the buried fiber right-of-way.