Multiple Dwelling Units (MDUs) represent prime targets of opportunity for service providers pushing the benefits of optical fiber directly to multiple living areas. Whether the MDU is a high-rise condominium structure or a row of townhouses, the potential return on investment has been increased by new products and systems that save money and reduce installation time.

During the last few years, even though MDUs showed promise as big revenue generators, fiber installers quickly discovered this market also presented significant challenges not faced with typical Fiber-to-the-Home (FTTH) applications. Among other issues, network installers want materials designed specifically with MDUs in mind – enabling them to get in and out quickly, save on associated costs, and still provide a first-class, reliable network.

This article addresses the specific challenges of installing fiber into MDU environments and new innovations in products, systems and practices that are becoming the standard for these applications. In just a few short years, the MDU fiber market has evolved from highly challenging to highly lucrative – and much of its new focus can be contributed to the availability of products designed specifically with MDU deployments in mind. Four specific categories of new innovation for MDUs include molding systems, bundled drop cables, plug-and-play architectures, and the main catalyst for fiber deployment in MDU environments – vast improvements in reduced bend radius fiber technology.

Behind the Scenes
Although network providers quickly figured out ways to bring fiber into living units within MDUs, several inefficiencies were identified along the way. One such inefficiency was in using off-the-shelf molding systems, such as metal tracking systems or rectangular hinge molding, to hide the fiber for aesthetic purposes. Legacy molding products are simply not specifically designed for routing small form factor cables or fibers throughout a building.

With the rapid growth of the FTTH market in recent years, manufacturers are finding opportunities to develop and market products designed especially for these applications. This includes new molding systems that are smaller, easier to install, and perfectly suited for MDU environments where fiber cables may be deployed down long hallways and into multiple living units.

Instead of the rigid 6- or 8-foot lengths of traditional molding materials, more flexible designs are hitting the market. Spooled moldings are being introduced that enable installers to simply spool off the specific lengths of molding required and fasten them to the wall, creating a smaller, seamless, more aesthetically pleasing pathway to each living unit.

Once the pathway is established in the MDU, installers want to install drop cables to each living unit as rapidly and efficiently as possible. The traditional method of taking single-fiber drop cables to each living unit and installing them one at a time is both time consuming and costly. Deploying fiber to 10 living units down 1 hallway would require 10 individual drops, each cut to the proper length.

A more efficient method is to bundle the individual fiber drops together as a single cable that can be used to access multiple living units. The single cable bundle is installed the length of the hallway, and a single fiber is accessed and cut in front of each living unit. A connector is field-spliced to each single fiber drop, making every drop cable easily connected to an access point at each living unit whenever services are requested.

For example, at the third living unit, fiber 3 would be cut from the bundle and a connector attached. The connector would reside in a small storage box at the access location outside the living unit. Once services are requested, a connectorized drop would be plugged into the access point and deployed into the living unit to the Optical Network Terminal (ONT) location.

This method is particularly useful in brownfield locations where installers do not have the luxury of accessing each living unit with fiber during construction. Besides allowing fast connectivity when services are requested, it also enables the installer to use smaller fiber cables, such as 1.2-mm cables that are too small and fragile to use individually. But when bundled together, they are much stronger while still easily fitting under the molding system.

Plug-and-Play Solutions
Today, the most cost-effective method of installing fiber throughout an MDU structure is to employ a plug-and-play architecture. Fiber is being installed closer to the end user than ever before. Plug-and-play drop cables allow quick and easy installation from any outdoor fiber distribution point for any size and style structure all the way to multiple user living areas. (See Figure 1.) Eliminating splices by using pre-connectorized cables saves money in several ways. Obviously, the more splices required, the more costs they incur. But there is also savings associated with the skill sets needed to make the connections. While it takes a unique (and potentially expensive) skill set to splice each connection throughout the MDU network, virtually any level technician can join two fiber connectors.

A new plug-and-play device that solves several issues of getting fiber to living units at various distances from the Fiber Distribution Terminal (FDT) is a spooled wall plate. The plate stores up to 200 feet of reduced bend radius fiber drop cable with SC connectors at each end. The wall plate is placed at each living unit with just enough fiber spooled out to plug into the FDT. The remaining fiber is stored right on the spool. When service is requested at any living unit, a single-fiber, plug-and-play drop cable is easily connected from the wall plate to the ONT within the living unit.

Along with new optical cabling techniques, there also are new innovations with active components designed for MDU applications. Desktop ONTs are gaining in popularity and offer another plug-and-play opportunity for installers. Again, designed with brownfield applications in mind where access panels and power outlets are not always readily available, the desktop ONT can be located on a desktop or other accessible location and simply plugged into any available power outlet.

However, locating ONTs on desktops makes fiber routing a bit more challenging. Fiber must be routed in open areas to reach the ONT, making it vulnerable to potential outside forces. Figure 2 shows how the plug-and-play drop cables can easily be stapled to surfaces, allowing easy access to connectors for quick service turn-up. One new architecture is to run a bundled multi-fiber drop cable past the living unit, drop off one connectorized fiber at the living unit, and run the drop from that access point to the desktop ONT. This would require a more robust single drop cable from the access point, such as a 3- or 5-mm cable.

Makin' It Happen
The main player in making huge strides in MDU fiber applications is the fiber itself. None of the new techniques and products would be possible without the recent breakthroughs in reduced bend radius fiber technology. The ability to bend fiber more tightly without a discernable increase in attenuation has opened the floodgates for bringing fiber to MDU structures.

Since MDU applications require many more twists and turns as the fiber is routed inconspicuously throughout the structure, using reduced bend radius fibers should be the standard practice. It should also be noted that although these fibers are capable of meeting the fiber routing challenges within MDUs, they are still glass and they can still be damaged. In fact, the requirement to hide the fiber behind moldings, baseboards, and other areas to improve aesthetics presents its own dangers. Nails or staples can still damage the fiber, as can inadvertently pinching cables between walls and moldings.

So while the accomplishments of these fibers are to be applauded, it would be a mistake not to adhere to the fundamentals of proper fiber cable management. In fact, as reduced bend radius fiber finds its way into more and more MDUs, both brownfield and greenfield structures, factors such as easy connector access and simple routing paths will become even more critical for network reconfigurations, troubleshooting, and maintenance. Reduced bend radius fiber is just one aspect of a complete strategy for efficient, future-proofed network management for the MDU environment.

It is estimated that more than one third of all U.S. households are located in shared MDU structures. This fact has not escaped the attention of broadband service providers seeking the most lucrative markets for their services. But while MDUs of different shapes and sizes uncover new challenges with each deployment, new product innovations are emerging that meet the challenges and help installers save time and money. From creative new molding systems and bundled multi-fiber drop cables to spooled wall plates and unique living unit solutions, service providers are discovering how to "fiber up" MDUs in record time while saving capital and operational expenses.

Although one optical proponent once boasted a slogan of "Fiber to the Fridge", the typical mindset has always been that fiber would never actually be pushed all the way to the residential living unit or handled by the consumer. Although we're not there yet, these new products, systems and technologies have taken us very close. It's no longer hard to imagine consumers purchasing self-install fiber kits at the local hardware store and making their own connections from a wall plate to their own ONT.
 

About the Author
Tom LeBlanc is an FTTX market manager for the Global Solutions Group at ADC headquartered in Eden Prairie, Minnesota. For more information, visit www.adc.com. 

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