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4. Gigabit Passive Optical Network
Gigabit Passive Optical Network (GPON) is the common name for the ITU-T G.984 standard for
bridging the access gap from a customer’s home to the CO with fibre.
GPON is a Point to Multi-Point (P2MP) type of architecture. A single fibre leaves the CO and is
passively split in the Outside Plant to feed 32 homes or small businesses.
GPON provides for throughput capabilities as high as 80 Mb/s downstream – 40Mb/s upstream, and
bursting up to a Gigabit per second.
All services are provided via IP over a high quality of service and secure Ethernet connection.
Figure 103: Passive optical network
Access area
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The generic architecture consists of four key locations and three cable sections. The Central Switch
Point (CSP), is usually a Central Office, Head End or remote terminal. It may be located on a metro
ring or other redundant link to the “core”. The CSP, which serves on the order of thousands of
subscribers, contains the electronics that form the provider side of the access network. The feeder
cable originates in the CSP and connects to the Local Convergence Point (LCP). The LCP is located in
a neighborhood or business park and serves many subscribers. Multiple distribution cables originate
from the LCP and radiate into the surrounding service area. Each distribution cable services many
Network Access Points (NAPs). The NAP is a closure or pedestal that access some of the fibers in the
distribution cable so that drop cables can be joined. The NAP typically serves 4-8 subscribers (but
can range up to 24). A drop cable is connected in the NAP and the routed to a Fiber Network
Interface (FNI) on the subscriber’s premise. The FNI may contain electronics that interface with the
subscriber’s premise wiring (fiber, copper, coax) or may be a passive interconnect used as a
demarcation point (in which case a short cable would run from the FNI to the subscriber’s
electronics, which may be inside the building).
