ISE Magazine, January 2019

JANUARY 2 0 1 9 WWW ISEMAG COM 4 1 DAMAGE PREVENTION kept in check through gnawing could rapidly lead to the animal not being able to open its mouth to eat causing certain death In the wild incisor growth is largely kept in check through activities such as the natural gnawing action that a squirrel undertakes to open a nut with a hard shell In an urban environment these animals may have at least part of their diet come from human sources food grown in urban gardens or discarded in the trash for example Such soft foods contribute nothing to curbing incisor growth making secondary gnawing an absolute necessity for the squirrel Solutions to the problems created by squirrels in cable plant have generally taken one of three general approaches These can be broadly categorized as lethal toxins physical barriers or repellents See Figure 1 Lethal Toxins Lethal toxins eliminate the problem by exterminating the rodent Clearly such a lethal approach ensures that the offending animal cannot repeat the behavior The downsides of introducing poisons into the environment are profound however Toxins may be inadvertently directly ingested by non target species including pets and even children Also by consuming the carcass of a poisoned rodent secondary species may also be killed For these reasons network operators particularly those in urban areas should avoid such risks Physical Barriers The physical characteristics of network cables play an important role in determining the need for additional protection against squirrel damage Cables with an outside diameter of 19 cm 075 or more are less likely to suffer squirrel damage for the simple reason that rodents cannot open their mouths wide enough to gnaw on them Unfortunately the fiber cables being pushed ever deeper into neighborhoods are being placed specifically because they carry a great amount of traffic while having a small diameter For these then a physical barrier repellent or combination of the two is required Physical barriers might include armor conduit and deterrents to prevent rodent access to the sensitive parts of a cable Armoring A common method of armoring is the use of corrugated carbon steel tape wrapper longitudinally around the cables core Because the tape is hard it can be fairly effective at limiting rodent access to a cables core Of course if a cables outer jacket is breached before the rodent is stopped by the steel corrosion from water may be a problem Conduit Extruded plastic ducts typically have an outside diameter that is large enough to make gnawing extremely difficult if not impossible Likewise triangular structures that exceed squirrel bite dimensions may be tented over the entire length of a cable discouraging the rodents mastication attempts Conduit solutions such as these can be effective but add cost and can be unsightly Further the added surface area of these solutions increase the wind and ice load of the cable presenting a more challenging OSP engineering challenge Bill ODonnell bodonnell@ abs go com Tim Cooke tcooke@ abs go com @ AmphenolBB Lethal Toxins Permanent elimination of offending animal May cause harm to non target animals and humans Physical Barriers In cable Deterrents Prevents chewing of cable core Gnawing could fully penetrate outer jacket allowing weather incursion Add on Deterrents Denies access to cables Added deployment costs Increased wind snow load Repellents Trains against repeated gnawing Depending on chemicals may require special handling Figure 1 General Approaches to Rodent Control APPROACH BENEFITS DRAWBACKS @ AmphenolBB