Several years ago, I received a phone call from OSHA asking me about aerial fiber optic cable installation. The concern was based on the recent electrocution deaths of two installers working with all-dielectric self-supporting (ADSS) cables on utility poles with a mixture of high-voltage and telecom cables. In both cases, the installers were attaching a type of fixture that was just a guide for ADSS cable to a pole.

If you are not familiar with ADSS cable, it is a special type of lightweight outside plant aerial cable designed for very high-tensile loads so it can be installed without a separate steel messenger to support it. It can be installed over very long spans, up to several kilometers in some cases, making it popular for use in rugged terrain to run between poles or towers, across rivers, canyons or other areas where supports cannot be easily installed.

Installing ADSS

Because ADSS cable is nonconductive, it can be installed on electrical transmission and distribution towers and poles, which is one of the most popular applications.

It is not supported by a messenger, so installation involves having the ends of the cable secured at a pole (called “dead-ends”) and intermediate poles have supports that allow the cable to be supported but allowed some slippage and sometimes to bend for changes in the direction of the cable.

ADSS cable can be installed in two ways: a stationery reel method, where the cable is pulled from one end of the span, or with a moving reel if the route is clear enough for a truck with a large reel of cable to pass, which is often not the case.

In the moving reel method, a pulley must first be installed on each pole to support the cable being pulled along the span. After the cable is pulled, the pulleys will be replaced by permanent cable supports.

It was at this stage that the two installers were electrocuted. The support hardware they were installing was a steel rod about 6 feet long with cable guides on each end and a single bolt hole in the middle for attachment to the pole. In both cases, the installer bolted the guide to the pole, rotated it enough to contact a high-voltage cable and was electrocuted.

It appears that type of support bracket is no longer used because of safety reasons. Today, the intermediate supports are typically small plastic or cast metal parts with rubber bushings, which are much safer designs.

Common practices and standards

But the installation of ADSS or any aerial cable on multi-use poles still requires working in the area below electrical wires, an area usually called the “telecom space.” It would seem obvious that a common practice such as separating high-voltage and low-voltage cables on poles or towers would lead to some industry standards. However, like the whole practice of aerial cable installation, it seems to have been ignored.

I recently did some research on this topic when a contractor asked about standards for aerial cable separations. What we found were some specifications set forth by local agencies or network owners, references to cable separation in OSHA regulations and the National Electrical Safety Code (NESC) and little else. I even asked my contacts at the Electric Power Research Institute (the Bell Labs of the electrical utility industry with whom I have been consulting on fiber optics), and they also led me to OSHA and the NESC.

I’ve seen several standards that purport to cover aerial cable installation, but they are basically 50s-era copies of telco specs on installing poles with no mention of the telecom space at all.

I’ve been asked by several people, including politicians, why aerial cables are such a mess. I’ve been asked why we don’t see more standards for aerial or underground cable installation. In fact, the whole topic of outside plant (OSP) fiber optic installation has been ignored by standards. The only purported OSP standard I know defines “OSP” as outside a building but limited to a campus. That is now how many installers understand OSP, but it represents only a small fraction of OSP installations.

Fortunately, electricians and electrical contractors are well trained in safety. They know to refer to OSHA and the NESC when it comes to topics like this, which is very good, because there is little guidance elsewhere.

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