Keeping up with fiber technology and applications is a full-time job. It’s one of several I have that keep me busy. Recently I have been corresponding with people from the industry and the Fiber Optic Association training organizations about changes happening and how we can address them. Not all changes are without controversy.

The FOA is sometimes the instigator of the controversy. One example is concern over the workmanship of aerial fiber optic cable plants. Last year, we huddled with our technical advisers around the world and came up with a series of guidelines for aerial cable workmanship. We ran it in the FOA newsletter with examples of bad workmanship. A version of those guidelines is in my article “Guidelines for Aerial Fiber Optic Cable Installation” on ECmag.com this month.

Exploring ADSS cable use

The newsletter article elicited a number of interesting comments from around the world. Some places, we were told, no longer allow aerial cables at all, so every cable goes underground. Some do not allow overlashing where new cables are lashed on top of current aerial cables. Other places no longer use “strand and lash” aerial cables where a fiber cable is lashed to a wire messenger; they only use all-dielectric self-supporting (ADSS) cables, which do not require a wire messenger. One reason was some areas where cables are installed are prone to lightning, a problem with the conductive messenger wire. 

I thought I understood ADSS cables, but I wondered why they were generally only recommended for use by electrical utilities in the power space on poles. Theoretically, ADSS cables are cheaper and easier to install, so the question is why they are not used more often. I tracked down some applications engineers from a cable company that makes lots of ADSS cable and asked them.

ADSS cables are nonconductive so they can be installed in the power space, which makes them ideal for adding fiber optic cables to electrical transmission and distribution poles and towers. However, sag is a problem with mixing ADSS cables with strand and lash cables on a pole. A steel messenger wire can be tensioned to reduce sag, allowing a location closer to the ground. ADSS cables should not be tensioned as much, but allowing more sag can create a problem of mixing them with strand and lash cables or even maintaining sufficient ground clearance. If they are installed higher up in the power space, clearance is not a problem.

It occurred to me recently that ADSS cable could be the ideal solution for rural broadband. I was driving along a remote mountain road just off the Pacific Coast Highway in Malibu, Calif., when I noticed there were poles with electric wires but no telecom cables. 

Adding fiber using ADSS seemed like a logical solution—except the area has already been burned in a wildfire, and many wooden utility poles did not survive. But in the mountainous, rocky terrain, there is no way to put cables underground.

Micro and high-fiber-count cables 

I’ve also been investigating microcables and high-fiber-count cables. Both are similar; high-density cables are made possible by using bend-­insensitive G.657.A1 fibers, usually with a smaller 200-micron buffer coating to allow packing fibers more tightly in the cable. The boundary between microcable and high-­fiber-count cable keeps moving up. For some makers, it’s moved from 288 fibers to 432 or even 864 fibers.

These cables solve the problem of installing more fibers in already crowded underground ducts, avoiding construction to bury more ducts. To make space in current ducts, techniques were developed to remove current fiber ducts from conduits by pulling them out from one end and letting the fiber lay in the bottom, then installing microducts or fabric ducts to install more cables. 

Microducts and microcables are designed around blowing or jetting cables. While the two terms are sometimes used interchangeably, in general, blowing cables means supporting the cable on a high-speed airstream and pushing it through the duct. Jetting is similar but adds a plug attached to the end of the cable to help pull it through the duct. In some areas, microcables, microducts and blowing or jetting are used for installing most cables, but not commonly used in the United States.

Most microcables and high-fiber-count cables also use flexible ribbons. I’m hearing that some contractors prefer the old hard ribbon designs, claiming they are easier to splice. Now we are investigating why contractors are feeling reluctance to adapt to these new technologies.

jim hayes