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CenterFuse Broadband Feasibility Report requirements change—the laser serving that customer can be changed without affecting any other part of the network. The primary vendors in the Active E equipment market are Cisco, Calix, Adtran, and Nokia-Alcatel- Lucent. Since PON equipment has won a much greater market share than Active E equipment, this part of the industry has been in a bit of a decline for a few years. Gigabit Passive Optical Network (GPON) This is the primary giber technology used in the country to serve residential customers. GPON makes use of optical splitters so that as many as 32 customers can share the same fiber(i.e., light source). If fewer customers are served from the same light source there is more potential bandwidth for each customer. A GPON network can be designed in numerous configurations, but all designs include the same key elements. All networks start at a network core where the connection is made to the Internet. At this core, the ISP generally inserts the signals for the various products being delivered to customers. From the core there are direct fibers to Optical Line Terminal (OLT), which are the devices that provide the light source for customers. These OLTs can be located in the same location as the fiber core or else can be spread around in neighborhood nodes, generally in huts or large cabinets. There is one fiber leaving the OLT for each "PON"which is the local network consisting of up to 32 customers. These fibers go to splitter cabinets where each fiber is then"split" into the 32 separate fibers that go to customers. The splitter cabinets can be located at the same location as the OLT electronics, or they can be moved deeper into the network to be closer to customers. The name "passive" for the technology comes from the fact that the splitter site doesn't require electronics or power—the splitting is just what it sounds like—one fiber is spliced and split into 32 individual paths. The paths from the splitter are "home runs" meaning that there is a dedicated fiber between a splitter site and each customer. One of the biggest benefits of the GPON network is a savings in fibers in the network. Only one fiber is needed to serve an OLT and one fiber goes from the OLT to each splitter. The fiber is only divided into individual customer fibers at the splitters, which can be deep into the network. The GPON technology chosen provides 2.4 Gbps down and 1.2 Gbps upstream from each group of 32 customers. Another advantage of PON is the number of electronic interfaces is reduced by the split, since one laser at the OLT can communicate with up to 32 customers. Increased bandwidth can be gained by reducing the number of customers on a PON—reducing a PON to 16 customers would double the bandwidth available per customer. Most fiber builders today choose GPON for residential service because it provides acceptable bandwidth and is less expensive than competing technologies. One consideration when designing PON networks is the optical distance from an OLT port to the customer ONT; the design of the 2.5 GPON network includes allowance for 1.32 split and a distance limitation of 20 km (12.4 miles) design limit. Page 68