Challenges and solutions for cabling in multi-dwelling units

March 2, 2020
Getting fiber to the home is one thing. When the home is a multi-dwelling unit, getting fiber to reach households poses its own challenges.

By Patrick McLaughlin

Did you read all the predictions about how technology is going to change the way we live in work in 2020 and beyond? You might have read some on our website,, or countless other media outlets as we wound our way from 2019 to 2020. As I compiled several of those prognostications late last year, I kept in mind that sometimes the prediction ultimately is accurate, even if the technological path to the predicted outcome is not accurately forecast. I thought about that specifically because I was preparing material for this article on cabling in multi-dwelling units.

In the late 1990s, many future-gazers predicted that networking and network connectivity in residences would become increasingly important in the ensuing years. The primary reason for this anticipated need was because people would be working from home, and in order to approach the type of connectivity they’d have in a commercial office building, they’d need a wired connection of 10 or 100 Mbits/sec—and maybe someday even a gigabit. Eventually, telecom providers would deliver more than Digital Subscriber Line (DSL) speeds to residences. So building a home network, with a Category 5e connection in multiple rooms of the home, would equip the residence for the ability to work from the home.

Connectivity in the home

That’s what soothsayers predicted more than 20 years ago. And they got the ultimate need right; in-home connectivity is considered a necessity rather than a luxury by many. And teleworking is one capability that it affords, but there are may others. And the physical architecture of that connectivity is a far cry from a Category 5e outlet in a handful of rooms.

John George, senior director of solutions and professional services with OFS, provided insight during a recent interview: “There’s an increasing demand for high-data-rate services” in homes, including multi-dwelling units, he explained. Around the 2013-2014 timeframe, he said, several Tier 1 operators launched gigabit-speed services to the building. “In order to reliably get a gigabit-per-second service into apartments, fiber is the best way to go in terms of cost of ownership and upgradeability,” George said. The need for high-speed connectivity is driven by remote working as well as a host of other lifestyle activities. “We record kids’ sporting events and when we get home, put them into the cloud. We don’t want that upload to take forever,” he said. In addition to entertainment and social-media activities, applications including telemedicine (telemetry, video monitoring) and robotic personal assistants are driving, or are expected soon to drive, the need for high-speed upstream and downstream capability.

The Fiber Optic Association (FOA) addresses fiber-to-the-home in multi-dwelling units in its Reference Guide to Fiber Optics. In that guide, the FOA says, “Let’s assume we have fiber to the building. What’s next? We must decide how to deliver broadband to each unit in the building and then inside the unit.” The FOA lists the following six options: 1) currently installed phone lines using xDSL technology; 2) currently installed CATV or satellite coaxial using cable modem or Multimedia Over Coax (MOCA) technology; 3) installing wireless access points at appropriate points in the building connected by Ethernet, as is frequently done in hotels; 4) installing new Category-rated unshielded twisted-pair cable to each unit if the unit is within 100 meters and uses Ethernet; 5) installing new coaxial cable to each unit and using cable modem or MOCA; 6) installing fiber to each unit and mounting the optical network terminal (ONT) at or inside the unit.

“Options 1 and 2 eliminate the need to install new cabling, but assume the current cables are in good enough condition to carry the signal bandwidth required,” the Reference Guide states. “Options 3, 4 and 5 require installing new cables and furthermore, option 3 assumes adequate bandwidth over the wireless for typical users. It would probably be overwhelmed by video users.

“And options 1 through 5 require considerable investment in electronics, space to locate them and quality uninterruptible power at the building entrance facility. The actual network architecture is influenced by the choice of electronics. ONTs are available for single users or multiple users, allowing one to distribute ONTs in a building, for example to serve all the units on one floor with copper cables. However, these multi-user ONTs are going to divide up available bandwidth among the number of units served—perhaps not a problem if the system is offering Gbit/sec service to the ONT, but potentially a large problem, even today but certainly in the future, if the bandwidth allocated to multiple users is much lower.”

Going for fiber

The FOA puts forth the installation of fiber to each unit as a preferable option. “With option 6, we would generally assume a GPON [Gigabit Passive Optical Network] or EPON [Ethernet Passive Optical Network] system, although a point-to-point system can be used. In the case of a point-to-point system, fiber to the unit could entail either a switch in the MDU building itself or a large-fiber-count cable back to the central office or nearest switch.”

This section of the FOA’s Reference Guide to Fiber Optics is several pages in length. Among the other observations and recommendations in the section is, “The actual architecture will be influenced by the design of the MDU building and where and how it is convenient to install components for the fiber-to-the-home systems.” And, “Recent developments on distribution and drop components make MDU installations easier. Perhaps the biggest development was bend-insensitive fibers that allow the manufacture of drop cables in extremely small sizes that can be run along wall or ceiling junctions, around corners, placed inside baseboard or molding and even made with an adhesive surface that can be stuck directly on walls. Bend-insensitive fibers also allow the manufacture of small cables that allow opening at any location to break out one or more fibers for termination at that point and allow the whole cable to continue to another location.

“Like any fiber or cabling installation, the actual project will be unique but be able to incorporate ideas that worked well in prior projects,” the FOA says.

Cable and connectivity provider PPC authored a blog post titled “4 questions to ask when installing fiber in multiple dwelling units.” Those four questions are: 1) What route are you going to use vertically? 2) What route/method are you going to use horizontally? 3) Plenum or riser? 4) Do you have proper access to the buildings and to individual units?

In addition to raising those four questions, PPC offers advice for an MDU cabling project: “Always look to find the easiest path for fiber, even if that means making holes in the building. Figure out the path of least resistance. Every implementation is different, meaning that the planner and installer both need to think on their feet and be flexible when deploying.

“This is new to many crews, with different products and methodologies, meaning you need to invest in educating and training crews,” PPC continues. “Where before you could rely on brute force, now you need to think through every implementation. Don’t go cheap and dirty when picking products for your deployment. Instead, focus on time to install, reliability, and total cost of ownership. You only get one shot at this, so use the best product you can. Plan for it to be there for the next 40 years, and choose your suppliers accordingly.”

Low-profile options

Since 2012 OFS has offered the InvisiLight solution, which delivers optical fiber to each unit in an MDU. The solution has grown and evolved over those years, from the original InvisiLight ILU (indoor living unit), to the InvisiLight MDU solution introduced in 2015, the InvisiLight Drop solution introduced in 2016, InvisiLight Façade in 2017, and most recently the InvisiLight ILU 600 introduced in 2019.

When OFS introduced InvisiLight ILU in September 2019, the company said the system “is less visible and offers even faster and easier installation than the original InvisiLight ILU solution … The original InvisiLight ILU solution offers installers an innovative yet simple process to adhere a 0.9-mm-diameter optical fiber into crevices along ceilings and walls or moldings and walls. The solution offers a safe, protected optical-fiber link that is virtually invisible. The InvisiLight 600 ILU solution uses an even smaller 0.6-mm optical fiber with the same simple installation process and tools as the original. With less than half the volume and half the weight, storage inside the InvisiLight 80x80 module is more than doubled from 10 to 25 meters, installation is faster, and a new benchmark is set for visibility.”

OFS’s George recalled the solution launched in 2012 “in response to pain points in the market. Subscribers would order FTTx service, and the technician would show up to the home with cable and a staple gun. Many subscribers turned them away and cancelled the service.” The idea was to create a virtually invisible fiber in a 900-micron buffered white jacket and enable a fast, intuitive installation process.

“InvisiLight MDU includes 12 EZ-Bend fibers inside a 2-mm-diameter cord that is installed in the hallway of a building,” George explains. “It provides a low-cost, low-visibility way to provide cabling in hallways. It also addresses the pain point that in hallways, often there are no pathways for placing fiber. Building and installing molding is a time-consuming and expensive process. InvisiLight installs in molding or a crevice. It’s essentially invisible.”

A point-of-entry module above each doorway facilitates a factory termination of the fiber, and the InvisiLight ILU system is used inside each unit.

“It’s a plug-and-play system that doesn’t require field termination,” George says.

While nearly all InvisiLight deployments have been in residential environments, George points out that it can be deployed in passive optical networks within enterprise environments also.

The FOA offers a final piece of advice for MDU installations. “The most important part of the design of a project in an existing building is a walkthrough to familiarize yourself with the building. Inspect for entrance facilities, cabling pathways and locations for equipment on every floor. Look at several units to see if it is feasible to enter the unit and place equipment.”

Patrick McLaughlin is our chief editor.

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