Issue link: https://www.e-digitaleditions.com/i/1327492
January/February/March 2021 I 9 According to BICSI's Telecommunications Distribution Methods Manual (TDMM), 14th Edition, "Passive optical LANs are an implementation of PON technology for the enterprise LAN…PON technology has successfully matured into a true enterprise network architecture capable of delivering voice, data, and video services to the end user via a single strand of singlemode optical fiber cabling. A PON solution reduces physical cabling infrastructure, minimizes the telecommunications space requirements through the use of passive optical splitters, and reduces electrical power and HVAC requirements in the floor serving TR." The TDMM provides in-depth information of standards and best practices for all modern cabling designs and installations, including PONs and POLs, and should be followed as it contains details beyond the information herein. TRADITIONAL ETHERNET LAN, POL, AND GPON Most POLs are deployed in greenfield projects. However, there are a significant number of POL deployments in brownfield projects as well, replacing the traditional active Ethernet infrastructure. FIGURE 1: Traditional active Ethernet LAN architecture versus POL architecture. In a traditional active Ethernet LAN, a router in the core layer links to the campus or building aggregation switches in the distribution layer below. The distribution switches connect down to the access layer switches in the telecommunications closets that reside in the TRs. These backbone links are generally composed of optical fiber, often MMF. Copper cables extend from the telecommunications closets to the users. The standard POL architecture consists of optical fiber cables, a distribution infrastructure and two layers of main active components. Centralized active equipment, optical line terminal (OLT), and optical network terminal (ONT) peripheral devices ensure appropriate communication to and from the end user. This is achieved by the passive distribution of all ICT services via passive optical splitters over the company's entire cabling infrastructure (Figure 1). Traditional active Ethernet LAN architecture POL architecture For years, backbone/vertical fiber recabling was the only logical solution, and it was most likely a deterrent to POL adoption because of its costs and complexities.