Cable, installation issues next step in FTTP
The BellSouth/SBC Communications/Verizon joint fiber to the premises (FTTP) equipment request for proposal (RFP) doesn't cover fiber and cable. Even so, the three RBOCs are already discussing the outside plant issues surrounding their planned FTTP rollouts with fiber and cable suppliers. As these carriers and their vendors hone the business case for FTTP, a lack of standards for some promising technologies such as air-blown fiber (ABF) could serve as an impasse with the Telcordia-driven Bells.
The feeder portions of the three carriers' access networks are not entirely built-out with fiber. The distribution portions of the networks are almost all copper cable, and the drops—the 20 or so feet from the network access point to the premises—also are copper, with some coaxial cable primarily in the BellSouth network. To date, BellSouth has deployed the deepest fiber, passing about one million homes with its fiber to the curb architecture. As the FTTP initiatives start to roll out, carriers and analysts foresee a mix of aerial (copper rehabilitation) and buried (greenfield) fiber-cable deployments.
However, the FTTP initiative has not led optical-fiber market researcher KMI Research (Providence) to change its earlier forecast of U.S. fiber to the home (FTTH) deployments, which are estimated to range from 500,000 fiber-km on the low end to 3 million fiber-km per year, according to KMI senior analyst Patrick Fay.
The standard singlemode fiber used in most FTTP deployments in the United States today is sufficient for the shorter distances and less stringent system requirements inherent in these access networks.* However, low water peak fiber (LWPF), which offers additional operating windows by lowering the attenuation performance in the water peak regions, is emerging as the new standard for singlemode fiber, especially among the RBOCs, according to Fay.
Corning, which promotes its traditional SMF 28e for the access network, agrees that LWPF is a good choice as an upgrade option. "In the metro areas, it offers immediate advantages in that you can use the low water peak region to transmit where you couldn't before, so there have been some system designs—coarse WDM—where low water peak fiber has an advantage over standard singlemode fiber," says Bob Whitman, market development manager, broadband, Corning Optical Fiber. "If you look at these access networks, they are typically not built for more than three wavelengths. But if you look at how bandwidth will grow over time, the low water peak fiber could fit quite well in an upgrade path, potentially providing a wavelength to every house rather than sharing wavelengths among houses."
Improving the attributes that access systems are designed around—attenuation, bending, and geometry—is the primary focus for fiber advancements, according to Whitman. "Geometry is becoming increasing important, because as you get further out to the access networks, you have less and less skilled labor," he explains. "If you can make those fiber connections via connectors as opposed to splicing, then you can lower the cost. And that's what it is all about: making it as cheap and as easy as possible."
Lowering installation and labor costs is undoubtedly the biggest hurdle in the access space, and technologies that can help carriers justify the business case for FTTP are the focus of most vendors' research and development. "Fiber is not the gating factor, labor is," says Max Nelson, senior manager of strategic business planning at OFS (Norcross, GA).
Reducing "first installation costs" by deploying enough fiber to hook up existing customers in the feeder and distribution portions of the access network, while allowing for scalability as subscribers come online, may warrant the use of microduct cables in densely urban portions of the network. These compact cables can accommodate as many as 72 fibers in a single microduct, one of several in a standard inch-and-a-half conduit.
"I've been told that a lot of network operators want to use microducts for air-blown fiber," says KMI's Fay. "You can supposedly blow these microducts into a larger duct, and then you can blow the fiber in after that, so it is a quicker installation than the old version of kind of ripping up stuff and just putting it in."
"You have to have a threshold of anticipated fiber. If you are looking at fiber counts of 48 or 60 as the maximum amount that you need, then this is not going to work out financially," warns Pete Mahnke, market development manager, access networks, at Corning Cable Systems (Hickory, NC). "If you get in a situation of 144 fibers, or in that area, then it would be economically sound to use this type of technology."
ABF, which is used in public networks in Europe by British Telecom and in Japan, could lower access installation costs and enable network scalability and flexibility, according to proponents. A tubing system is installed, and a specially designed fiber is blown into the tubes when and where needed.
"If you blow the fiber [in the drop] your buried costs approach your aerial costs," says Nelson. "Plus under the regulations put forth on February 20 by the FCC, if an RBOC deploys dark fiber, then that fiber is subject to UNE [unbundled network element] rules."
However, ABF is not governed by any standards specifying requirements for the product itself or its use in the outside plant. The Insulated Cables Engineers Association is beginning to work on developing standards for ABF in its Telecommunications Wire & Cable Standards Technical Advisory Committee. The lack of standards may cause the three RBOCs to avoid such an approach.
Fortunately, optical drop cables designed according to Telcordia standards have been available and deployed to a limited extent over the last two years. These drop cables, which feature one or two fibers for FTTH and several fibers for multidwelling units and small businesses, are installed using basically the same techniques as a coaxial or copper cable, according to Mahnke.
*For more information on new access fiber technologies, see Lightwave, "Better access: Where no fiber has gone before," July 2003, p. 29.