Sunday, February 1, 2015

Blueprint: The Structural and Economic Benefits of Passive Optical LANs

by Stephen Porach, PE, RCDD, OCC, Manager of Business Development – Enterprise Solutions

With the rise of fiber to the home (FTTH) technology, the commercial sector is quickly jumping on the bandwagon. Optical LANs are rapidly replacing the traditional commercial network infrastructure with fewer components, decreased installation costs, operational efficiencies and a system that’s ready for future upgrades.

Derived from fiber to the home technology, Optical LANs, also called passive optical networks (PON) or passive optical LANs (POL), have been around for 20 to 25 years, but it wasn’t until recently that the technology had been scaled to bring cost effective, green connectivity to the commercial sector by replacing or integrating with existing network architecture.

Traditional network architecture in an Ethernet LAN typically consists of multiple levels of switch aggregation. Services, such as voice, data and video, are routed through a multi-link network that uses an enormous amount of copper cabling to connect users to local switches in IDF closets and/or telecommunication rooms throughout a building.  In multi-level buildings and large campuses, this can create a congested hierarchy of switches and cabling that all require space, energy and cooling.

POL eliminates the complexity of this architecture and offers significant energy and labor savings.

Introducing Passive Optical LAN

Contrary to traditional structured cabling, POL uses a slightly different architecture than networks requiring telecom rooms filled with switches. POL flattens the Local Area Network, by replacing switches for passive optical splitters, thereby eliminating the many challenges associated with conventional networks.

Upgrading to a POL solution is a seamless transition because it does not require changing, upgrading or supplementing user equipment such as computers, network printers or any other IP device.  Nor does it require replacement of the traditional core (WAN) switch, which is the company’s access point to the internet or cloud.  POLs simply take the place of all the intermediate switches and horizontal copper cabling.

An Optical Line Terminal (OLT) is connected to the core switch and serves as the center of the POL.  From the OLT, single-mode fiber is run to an optical splitter.  The optical splitter is used in lieu of the access switch traditionally located in the telecommunications room.  The optical splitter is a passive device that splits the downstream signals to all connected devices and it combines them for data flowing upstream.  By eliminating the aggregation and access switches, you eliminate the power, cooling and space required for that telecommunications room.

The signal is then distributed to Optical Network Terminals (ONTs), which may look similar to cable modems in a home, that offer standard Ethernet connectivity to end-users. At this point the copper Ethernet connection to the end user device can support Power over Ethernet (PoE), and can do so up to the standard 100-meter channel.  These ONTs can be located at the desktop, under it, or in a variety of different locations depending on the device or devices it is serving.

Passive Optical LANs require only a single strand of fiber to convey the signal in both directions by utilizing wave division multiplexing (WDM).  WDM utilizes multiple wavelengths of light on the same strand of fiber, allowing the downstream and upstream signals to co-exist on that single fiber strand.  This is somewhat different from how signals are transported on a more cumbersome conventional network where two strands are required, one for the downstream signal and one for the upstream signal.

What should you be looking for in a Passive Optical LAN provider

Cost Savings

Passive Optical LANs can provide significant savings to any organization. The savings are two-fold. There is the upfront savings to install the network and support structure, and there is a year-over-year operational savings.

Because of the ease of installation and maintenance, organizations using POLs will experience lower capital and operating expenditures over time compared to traditional cabling.

Additionally, optical splitters in the POL remove the need for switches and the backbone copper cable that runs from switches to end-user ports.

POL capital/operational savings originate from:

  • Optical splitters removing the need for expensive switches, compounded by the reduction in the power and cooling infrastructure required to support those switches.
  • Replacement of expensive copper cable with a less expensive, single-mode fiber cable. Furthermore single-mode fiber will not require replacement during future network upgrades.
  • Eliminating of large bundles of copper cabling reduces the infrastructure required such as cable tray, ladder rack, conduit and firestop systems to support the cable.

Easy Installation  

With the significant reduction in cabling in a POL solution, installers no longer have to pull miles of heavy cable and run that cable to thousands of Ethernet ports. As previously stated, the support infrastructure for those cables is also gone, eliminating multiple steps in installations and saving time for installers.

Additionally, modern optical fiber is lightweight, yet tough enough to allow you to pull and bend the fiber without damage to the operating performance. The bend insensitive optical performance of single-mode fiber allows these cables to be installed even in the tightest of spaces.  Moreover, the cables can be custom manufactured to be used in a variety of industrial and generally harsh environment applications.

Looking for a significantly reduced installation time? Utilize pre-terminated fiber assemblies. Large POLs have significant quantities of fiber terminations.  Pre-terminated assemblies decrease labor costs and significantly reduce installation time.


POL simplifies network moves, adds and changes without having to replace the cabling infrastructure. Single-mode fiber has more bandwidth and greater distance capabilities than any other medium on the market today. Once single-mode fiber is installed, upgrades are accomplished simply by upgrading the electronics (OLTs & ONTs).  This removes the need to replace outdated category cables when providing additional bandwidth to the end user. This fiber infrastructure should support the user longer than any other medium available, giving organizations a real motive to ensure they have a 25-year product assurance warranty issued with their installation.

In addition, many large campus networks have a single-mode fiber infrastructure already installed between buildings. Optical networks can span up to 30 kilometers and take advantage of this previously installed infrastructure.


Not only can organizations save on maintenance and installation, studies have shown POL can cut energy costs by up to 67 percent. Replacing a switch with an optical splitter, reduces power consumption and energy demands.

Flexible and Customized  

Passive Optical LANs can be configured specifically to user requirements, which is why deploying components from a full line manufacturer of POL products provides flexibility not found in conventional networks. POLs are scalable and can be modified, upgraded or enlarged with the user.  If telecommunications rooms are on-site, the infrastructure can mirror cable routing of a traditional LAN.  However, if organizations take full advantage of a POL solution, energy and space wasting telecom rooms are replaced with a zone enclosure located in the ceiling. The zone enclosures house the optical splitters and can be located throughout the user space depending on their unique requirements.

Passive Optical LAN Solutions Encourage Savings and Support Growth

POL’s are intended to support multiple applications, from mobile to desktop computing, as well as voice, IP and RF Video. Additionally, the single-mode infrastructure can be leveraged to support a Distributed Antenna System (DAS).

In general, organizations searching for a networking solution that is less costly, more energy efficient, easier to install, simpler to maintain and more secure than traditional cabling structures, should lose the telecom room and begin enjoying energy and cost savings today with a POL solution.

About the Author

Stephen Porach graduated from Rensselaer Polytechnic Institute in Troy, NY with a Bachelors of Science in Mechanical Engineering.  He worked for 6 years in the construction industry, and has now been employed in the telecommunications industry for 20 years in positions ranging from sales to engineering to marketing. He is a licensed Professional Engineer (PE) and a BICSI Registered Communications Distribution Designer (RCDD). Porach is currently Manager of Business Development – Enterprise Solutions at Optical Cable Corporation (“OCC®”).

About OCC
Founded in 1983, OCC is headquartered in Roanoke, Virginia with offices, manufacturing and warehouse facilities located in each of Roanoke, Virginia, near Asheville, North Carolina and near Dallas, Texas. OCC’s facilities are ISO 9001:2008 registered, and OCC’s Roanoke and Dallas facilities are MIL-STD-790F certified.

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