With 80% of a telecommunications build being spent on labor, conducting a thorough analysis of labor costs is critical to the containment of deployment costs. A deployment requires a staff of planners, engineers, field crews, and construction forces who are knowledgeable about the type of services to be offered and how they are to be delivered.

Little attention has been placed on the underlying foundation of these networks: the protection and management of the physical layer. The physical fiber network must be protected as light passes from one point to the next, ensuring as minimal degradation of signal as possible. It is crucial that any place in which a fiber is terminated, connectorized, or spliced, that adequate fiber management practices are followed.

With the increased usage of bandwidth, carriers are finding it necessary to reinforce their networks simply to keep up with the demand. If you haven’t noticed how this has happened, just look to your kids. The younger generations are using their cell phones more and more, and letting the laptop and the desktop computer sit idle. This increase in usage has pushed an already strained network to the limit. Add to this the lack of available space in both buildings and downtown areas and you get a recipe for major network failures. To combat this, carriers are looking for creative ways to maximize existing space and reinforce their fiber with new and innovative technologies.

An emerging technology is pushable fiber coupled with a microduct solution. Not to be confused with air-blown fiber, pushable fiber is a practical solution that not only allows for cost-effective deployment of fiber in cellular backhaul and DAS networks, but also provides ongoing returns by reducing the costs of maintenance and restoration.

Distributed Antenna Systems (DAS) Means Getting Fiber to the Cell Site
DAS is an exciting technology that allows for greater coverage and backhaul services in metro areas where wireless technology coverage has a hard time reaching. DAS also provides sufficient backhaul services where large amounts of cell traffic are infrequent, but required, such as sports venues. The challenge in a DAS environment is getting fiber first from the DAS control unit back to the base station and then to the antenna sites (depending on whose technology you are using) as they are commonly situated in or on structures that are encased in concrete.

A relatively new and cost-effective method when deployed in the OSP-DAS (ODAS) is micro trenching (slot cutting). With this method, a microduct from an existing manhole run where there is plenty of fiber and placing a fiber from the manhole splice into the DAS equipment on streetlight poles. The challenge is typically finding the time and or space to do this.

Traditional trenching is an expensive and labor-intensive process. It has become such a sore spot in the deployment of cable that even Wikipedia (www.wikipedia.org) has gotten into the act, providing a 14-step process on how to plan your excavation. Challenges associated with soil types have been well documented, as well as the laborious steps associated with creating the support structure to prevent cave in, dewatering, and/or benching the excavation.

The need for pushable fiber and microduct is obvious when there simply is no room for a larger, typical outside plant solution. The traditional method of digging a 1-foot-wide trench, placing a 2-4 inch conduit, backfilling with concrete and then repaving is long gone. This older method typically costs upward of 60% more to do, and also impacts the local traffic in ways that just are not acceptable anymore. (Imagine closing a lane of traffic in downtown Chicago for a week.)

With the pushable fiber method, a slot is cut, usually at night, and then 2 microducts are placed in the slot. One of these microducts typically has the ability to be located. This is critical, as when fully restored it’s virtually impossible to see where the trench is and after a season of resurfacing, it will be fully invisible.

Micro trenching is a better alternative as it is less time-consuming, less invasive, and allows for traffic to pass over the trench line without worry of causing damage. The trench width is usually 1 inch or less, and since less material is removed, it can be easily restored.

After the microduct is placed in the trench, a small hole is bored into the manhole where the fiber ring is located. The microduct is placed into the splice case, just as a traditional cable would be, then the fiber is simply pushed through the microduct and spliced as a normal cable.

The 3 most attractive qualities of pushable fiber are:
1. It allows for installation from either end, thus letting the installation crew work with the least amount of disruption.
2. It is a good size. A 3mm pushable fiber can house up to 12 fibers, while a 4mm can house up to 24 fibers and still fit into a 10mm microduct.
3. The placing of 2 ducts in a small, 1-inch footprint allows for the project to be completed in a normal shift overnight, thus reducing the impact on the local traffic and all the associated headaches that come with traffic control.

Cellular Backhaul: Reinforcing an Existing Duct Structure
When the requirement is for fiber reinforcement in an existing duct, the requirements change somewhat but there are still some common threads. Consider a structure, such as a rooftop site. When you think about it, the lack of space and the costs associated with constructing new pathways through the riser space in buildings is just as prohibitive as digging up city streets.

Pushable fiber addresses this much in the same manner by installing microducts inside the existing structures to provide a distinctive pathway. Using the pushable fiber, the fiber is pushed from the top down. The added benefit of installing it in buildings is that it works with gravity. Given the small size of the pushable fiber, you can easily carry it to the top floor and let gravity help with the installation.

An installation in Racine, Wisconin, serves as a good example. This particular cell site was on top of a 10-story building with a 1-inch conduit running down from the rooftop to an equipment room in the basement. The connection point for the local telco was an additional 450 feet away in a manhole. This installation had been on hold for 3 years because of routing problems and the costs associated with core drilling 10 floors and installing a new conduit. Using the pushable fiber alternative, the task was accomplished by placing both the microduct and fiber in about 8 hrs.

Aerial or Underground Option for FTTC
Reducing the labor cost of installing fiber from the access point to the tower or DAS antenna, while improving the long-term reliability of that fiber, is the promise of an optical fiber protection system deploying pushable fiber. In fact, by eliminating splicing, pushable fiber within a ruggedized microduct can eliminate hundreds of dollars in labor costs at every connected fiber.

In its simplest form, ruggedized microduct is either aerially installed or direct buried and the pushable fiber is either pushed by hand or machine to its desired end-point -- up to 1,500 feet. The pathway can transition from outside (aerial or buried) to an inside plant environment with a simple airtight and watertight coupler that requires minimal tools to install, allowing for a single and continuous pathway. Pushable fiber is available in bulk form or terminated with a unique pushable-connector -- as a single drop or multi-fiber assembly.

The need for fiber is clearly demonstrated at cell sites and DAS antennas, but the cost-effective means to delivering that technology is less understood. In the examples given, pushable fiber and microduct solutions, when combined, not only saved money for the carrier, they impact the people who are being better served by the installation.

While DAS usage has increased significantly and still shows a monumental growth potential, the technologies that support it are going to need to catch up. The good news is that all carriers agree that DAS usage will continue to increase for quite some time and they are making significant investments of both time and money to fully deploy a future-proof network.  (Now where have we heard that term before?) What this means for manufacturers and vendors is that the products that are produced to support this technology will need to be thought of in a way that expandability and ease-of-deployment/restoration are in the forefront. Traditional fiber cables can be adapted to use in both DAS and fiber to (and up) the cell tower, and can be a stop-gap technology. However, products specifically designed for the cell site need to be considered if we are going to, as manufacturers, truly support our carrier partners.

Looking forward at the DAS market, a plug-and-play technology lends itself very nicely, and provides for limited time on the build for the technician, and also allows for quicker expansion and upgrades if needed.

 Scot Bohaychyk is Product Marketing/New Products Manager for Clearfield. He has more than 27 years of experience in Telecommunications and Outside Plant Construction and Engineering. For more information, please email sbohaychyk@clfd.net or visit www.clearfieldconnection.com.

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