The GPON (Gigabit passive optical network – ITU-T G.984) standard differs from other PON standards in that it achieves higher bandwidth and higher efficiency using larger, variable-length packets. GPON offers efficient packaging of user traffic, with frame segmentation allowing higher quality of service (QoS) for delay-sensitive voice and video communications traffic.
How GPON Works
Downstream signals are broadcast to each premises sharing a fiber. Encryption is used to prevent eavesdropping. Upstream signals are combined using a multiple access protocol, invariably time division multiplex (TDMA). The OLTs “range” the ONUs in order to provide time slot assignments for upstream communication.
Cable operators have a variety of options for deploying the capacity necessary to support bandwidth-intensive consumer and enterprise video and data services. But one stands out: GPON, which provides downstream speeds of 2.5 Gbps and upstream speeds of 1.25 Gbps. That’s ample bandwidth for a variety of consumer and enterprise applications, ranging from HD VOD to HD videoconferencing.
Deploying GPON from the beginning allows JTL to upgrade its infrastructure to also accommodate new high bandwidth services that will come on stream in the future.
GPON is a proven technology, with standards finalized in 2005. The first commercial, full-rate GPON deployment in North America launched in June 2006. This and subsequent real-world deployments have proven GPON’s ability to support mission-critical carrier and enterprise applications.
GPON easily supports a mix of voice, video and data services, so it’s an ideal foundation for triple-play services. In fact, the ITU created GPON with multiple services in mind. Triple-play services are increasingly important to cable operators because they increase average revenue per subscriber (ARPU) and because the more services customers get from a single operator, the less likely they are to churn.
GPON leverages fiber, including a variety of implementations, such as fiber-to-the-home (FTTH). Unlike copper-based technologies, GPON doesn’t suffer from decreasing performance over distance, so subscribers located within 20 km of the centrally located optical line terminal (OLT) enjoy the same performance as those located next door. The OLT typically receives data – including video – via a high-capacity metro ring or long-haul transport facility. So as long as the transport can be arranged.
GPON can provide high-bandwidth services to smaller population centers that previously were too remote to meet the ROI requirements of large operators. GPON also leverages fiber’s cost, which is comparable to that of copper. However, fiber is more cost-effective over the long run because it has ample headroom to support future services, while copper will never have the same capacity as fiber.
GPON leverages PON’s low opex and capex, including low subscriber-equipment costs. PON subscriber equipment and network infrastructure also are passive, which translates into low maintenance and replacement costs because there aren’t active components to fail. All of these savings improve the cable operator’s ability to price its video and broadband services competitively yet profitably.
GPON is inherently secure, with wiretapping and other hacks nearly impossible. That security is a major asset when selling into the enterprise services market.
In addition to providing the most efficient transport of packet data such as Ethernet , GPON’s standard protocols inherently support synchronized TDM services such as voice and T1 lines, providing additional flexibility to accommodate the types of business services cable operators offer, including legacy TDM and evolving applications such as Ethernet connectivity to cellular base stations.
GPON supports higher infrastructure density than point-to-point fiber deployments, saving valuable space in headends and other facilities.
GPON equipment is available from a large and growing number of vendors, and it is standards-based. This combination of vendor support and standardization gives cable operators peace-of-mind because going with GPON doesn’t mean being locked into a small vendor universe.
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