Triple-Play Service Deployment

Chapter 3: Deploying and Troubleshooting Fiber Networks
A splitter’s primary benefit is that it is a passive component,
requiring no maintenance and no power activation. Its primary
drawback is high rate of insertion loss. Insertion loss is defined as
10log(1/n), where n is the number of ports (2 to 64). Table 3.3
shows the expected insertion loss that corresponds to a specific
number of ports.
Number of ports Insertion loss
2 3 dB
4 6 dB
8 9 dB
16 12 dB
32 15 dB
64 18 dB
Table 3.3 Expected insertion loss based on number of ports
This insertion loss factor has a high impact on the transmission
distances for FTTH, essentially limiting the achievable span length
to a distance of approximately 20 km (30 dB maximum network
insertion loss).This distance limit also takes into consideration that
low-cost components are often used at the OLT and ONT.
PON Signals and Network Structure
In a standard PON system (see Table 3.2), also called an optical
access network as defined by ITU-T G.983.1, the central office (CO)
is interfaced to the public switched telephone network (PSTN)
using DS-X/OC-Y signals and is connected to ATM or Ethernet
interfaces. Data and voice signals use the 1490 nm wavelength for
downstream signals and the 1310 nm wavelength for upstream
signals. Video services enter the system from a cable television
headend or from a satellite feed. Video signals are distributed via
the 1550 nm wavelength (downstream signals only).
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