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Stimulating Advances in Optical Network Deployments

Mon, 11/30/2009 - 7:25pm
Barton Filipiak, market development manager at Corning Cable Systems

The American Recovery and Reinvestment Act of 2009 (ARRA) sets aside $7.2 billion specifically for investment in broadband connectivity for unserved and underserved areas. As I write this, the first round of submissions has closed, but the NTIA and RUS have not yet released any funds. The general consensus is that requests proposing wireless last-mile technologies will command a significant portion of the available monies.

Fiber-optic cable will likely make up the bulk of middle-mile infrastructure due to its inherent reliability and scalability. We'll examine some of the advances in fiber-optic products and installation practices to help ensure stimulus money winners get the most bang for their buck.

Submissions for the first round were due in August, and the NTIA and RUS will begin announcing winners in mid-December. A point system was used to narrow down the field of applicants, and to eventually determine the winners. Proposals that provided the highest-possible bandwidth in the middle mile are more likely to win than those that did not, and extra consideration is provided for more scalable technologies.

Another condition of the ARRA is that funded projects be two-thirds complete within two years of the date the monies are issued and fully complete within three years. While that may seem like a long time, for projects of this scale, it really isn't. Several factors will cause unforeseen delays, such as route approval, access and make-ready work. No one can dispute that the most expensive part of any infrastructure project is the labor associated with deployment; downtime and delays further exacerbate this concern.

Low-loss optical fiber has been around since the late 1970s. While there have been advancements in optical performance, the underlying principles remain the same. The only limitations on networks using single-mode fiber are those associated with the equipment connected to the ends. This means that in order to upgrade these systems at some point in the future, we only need to replace the equipment on the ends. We frequently read about the expense associated with deploying optical fiber, but when you consider the longevity and network resilience it enables, it really is the best option. Optical cable installed today will be able to handle bandwidth demands well into the future - in all kinds of weather, with no degradation in throughput.

Let's examine a few of the ways stimulus fund winners (and everyone else) can lower total installation time and expense.

In the early days of optical cable, increased fiber count meant dramatically increased cost. Cable MSOs deployed countless thousands of miles of optical cable throughout their footprint, most of it only containing six fibers. Hybrid fiber/coax (HFC) networks were only going to distribute one-way video programming, and the Internet had not been invented. Six fibers were more than they would ever need for that purpose. Field splicing was incredibly expensive and time-consuming then, as well, particularly when a technician could only splice one fiber at a time. While it is certainly not a recent technology breakthrough, deployment of ribbon cable designs can dramatically reduce field labor expenses, and the reduced cable diameter means more fibers can be pulled through smaller conduits when compared with standard loose tube cables.

A more recent improvement in outside plant cable design is the move to enhanced, or dry, cables. The "icky-pic" we've all come to know and love has been replaced with dry film that gels if it comes in contact with water. They both equally prevent water migration, but cables equipped with dry film are much easier to handle. Before a cable can be spliced or terminated, the traditional gel-filling compound has to be completely removed and the fibers diligently cleaned before splicing or terminating. This process is incredibly messy, and utility companies routinely pay high-cost technicians a good bit of money to remove it. Newer dry cables require less equipment and less time to prep and splice cables. Furthermore, today's enhanced dry cable designs are also smaller and lighter than ever before, saving storage space and shipping expenses, as well.

Even more money can be saved if ribbon cable designs are used for high-fiber-count segments. While not exactly nascent, ribbon technology does offer several advantages and is often overlooked as a viable option when designing cable plant. The biggest advantage of ribbon cables is that instead of splicing a single fiber at a time, technicians splice 12 fibers at once and then protect that splice with a single heat-shrink splice protector. Ribbon cables are also available in dry designs to even further reduce installation cost. Despite the slightly higher cost of the cable itself, total installed cost can be as much as 30 percent lower than standard cable (see Figure 1).

Total Deployed Cost Comparison...
Figure 1: A 3,000-foot total installed cost comparison
of ribbon and loose tube cable

The underlying principles in optical cable remain generally unchanged, but the methods we use to deploy those systems have changed dramatically since the late 1970s, and particularly in the last few years. Optical fiber is only useful when a connector is installed and subsequently plugged into some device, and there are several means of installing those connectors. While I'd like to say there is a termination process that excels in all areas, there is not. As with most things in life, there are tradeoffs we must weigh in order to choose the best solution for our particular situation.

Spliced pigtails may offer the lowest loss, but they also require specialized equipment, a skilled splice technician, and additional hardware to store and protect those splices. Field-installed connectors do not require additional hardware to protect any splices, but there is increased variance in quality. I remember the first fiber-optic installation class I ever took. I was in the Air Force in the mid-1990s, and we were taught to splice, terminate and test optical fiber using the most advanced tools of the day. The most common connectors then required epoxy and a hand polish.

I remember loading fibers into a connector ferule, then using a scoring tool and a series of lapping films to eventually (and hopefully) put a perfect polish on the connector. Success was not guaranteed, and we scrapped several attempts before actually getting a good connector. No-epoxy/no-polish connectors were something new at the time, and their longevity was frequently questioned despite the amount of time saved. No-epoxy/no-polish connectors have come a long way since then and have proven themselves in the field time and again. Touting nominal performance values dramatically below published EIA/TIA specifications, these connectors offer perhaps the best compromise of performance and installation cost. With today's tools, a technician with minimal experience is able to reliably terminate optical cable with standard flat- and angle-polished connectors at a typical rate of one per minute. The handheld tools, some of which include a go/no-go indicator built right into the termination tool, simplify and expedite the connection process.

Then & Now Tool Kits

The most recent advance in optical cable is pre-spliced cable assemblies where connection points are predetermined. Instead of buying reels and reels of bulk cable, installing it, cutting it to length and splicing it, a pre-spliced cable assembly is loaded onto the truck and rolled off along the designated cable route. All the splices are already where they should be, spliced and tested at the factory.

A common argument against this technology is the level of accuracy required with pre-engineering; since the cable assembly is pre-spliced, there is less room for on-the-fly changes. But here is something else to consider: How much cable splicing can normally be accomplished while make-ready work is being approved and performed on pole routes or while hand holes are being placed? Normally ... none. Why not use that valuable time to have the cable pre-spliced and tested before it ever leaves the factory? When the make-ready work is complete, the cable can be installed in blitzkrieg fashion, generating revenue much more quickly than field-spliced cable.

What happens if the cable is somehow damaged later on? The same thing that happens to any other cable: You repair it. It is still regular cable, and the same equipment that has always been used on optical cable can be used on it, as well. Pre-spliced assemblies also save time by utilizing hardened connector technology, which means end equipment can be connected in a matter of minutes by virtually anyone. This leads to an overall first install cost that is as much as 50 percent lower than traditional spliced-cable deployments.

Standard vs. Pre-Spliced Outside Plant Installations

Fiber-optic cable remains the premier choice for data network infrastructure the world over, and while we will never be able to completely eliminate installation costs, we continually aim to reduce them whenever practical.

These are only a few product and technology enhancements that keep deployment costs as low as possible, while simultaneously reducing overall installation time. The NTIA and RUS will distribute ARRA funds according to which proposals best meet their criteria and which organizations are most likely to complete these projects within the specified timeframe at a reasonable cost.

If you are one of the entities selected for loans or grants under the ARRA, utilize these tools to help extend those dollars - and your network.

E-Mail: barton.filipiak@corning.com

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