H3C Technologies H3C S7500E Series Switches - Manual (Page 35)

2-2
Figure 2-1 A typical EPON architecture
ODN
OLT POS
ONU2
ONU1
ONUn
OLT
An OLT, generally an Ethernet switch, router, or multimedia conversion platform, is located at the
central office (CO) as a core device of the whole EPON system to provide core data and
video-to-telephone network interfaces for EPON and the service provider.
ONU
ONUs are used to connect the customer premise equipment, such as PCs, set-top boxes (STBs), and
switches. Generally placed at customer's home, corridors, or roadsides, ONUs are mainly responsible
for forwarding uplink data sent by customer premise equipment (from ONU to OLT) and selectively
receiving downlink broadcasts forwarded by OLTs (from OLT to ONU).
ODN
An ODN consists of optical fibers, one or more passive optical splitters (POSs), and other passive
optical components. ODNs provide optical signal transmission paths between OLTs and ONUs.
A POS can couple uplink data into a single piece of fiber and distribute downlink data to respective
ONUs.
Benefits of the EPON Technology
Lower operation and maintenance costs
Compared with a traditional Ethernet broadband access network, an EPON network greatly lowers the
operation and maintenance costs. This is because, as passive equipment in an EPON system, POSs
are energy-saving (requiring no power supply), highly reliable (not affected in case of a power outage),
and easy to install, and save optical fiber resources.
Long distances and higher bandwidths
Compared with an Ethernet broadband access network, an EPON system provides a longer access
transmission distance (up to 20 km, or 12.43 miles) and higher bandwidth (1 Gbps) that can adapt to
the service status of the ONUs in real time. Each ONU enjoys dedicated line quality similar to Time
Division Multiplexing (TDM) with dedicated uplink bandwidth in the grant cycle assigned to it.
EPON Application Mode
Based on where ONUs are deployed, EPON application mode can be Fiber To The Curb (FFTC), Fiber
To The Building (FTTB), and Fiber To The Home (FTTH).