Riverstone Networks WICT1-12 - Manual (Page 115)

Riverstone Networks RS Switch Router User Guide Release 8.0 7-3
CMTS Configuration Guide Provisioning the Headend
7.3.1 Headend Certification
The cable headend plant must pass both analog and digital certification. In the United States, analog certification is an
annual measurement procedure mandated by the Federal Communications Commission. Consult with local agencies
for local analog certification requirements.
7.3.2 IF-RF-Upconverter
The downstream output of the CMTS module is 44 MHz IF (intermediate frequency). To be compatible with cable
television system frequency division multiplexing, you must install an external IF-to-RF upconverter that translates
the IF signal to RF carrier frequency. The upconverter also allows you to maintain your existing channel lineup.
Upconverters are available from many manufacturers and can be found in configurations ranging from a fixed number
of ports to flexible multislot, multiport models. You must install and configure enough upconverter ports to support
the number for downstream CMTS line cards installed in each RS 8000/8600. The number of upconverter units you
will need to purchase depends on the manufacturers. The upconverters you use in your installation must support 64
and 256 QAM digital signals
An analog channel modulator with external IF-loops is not suitable for use as a digital QAM upconverter. These units
typically do not have the phase noise performance levels required for 64 and 256 QAM digital signals, and they might
cause lower performance and possible system failure.
The upconverter is installed between the CMTS and the combiner as shown in Figure 7-2 . The combiner refers to all
the cables, amplifiers, and taps at the headend or cable distribution center that connect the CMTS to the hybrid fiber
coaxial network.
7.3.3 Diplex Filters
A diplex filter must be installed in the RF path between the CMTS modules in the RS 8000/8600 chassis and the cable
modems. Diplex filters are used to separate the high-band frequency downstream signals from the low-band frequency
upstream signals. High-band signals flow in the downstream direction from the RS 8000/8600 to the cable modems,
and low-band signals flow in the upstream direction from the cable models to the RS 8000/8600.
A simple example is when the input of the diplex filter consists of three ports: the high filter port, the low filter port,
and the common port. The common port (the output) is connected to a splitter. Unused connection ports on the splitter
must be terminated.
The downstream output signal from the RS 8000/8600 runs through the upconverter, and then enters the high filter port
on the diplex filter. The signal exits the common port on the filter and is distributed to the cable modems. The upstream
signal from the cable modems enters the common port of the diplex filter and flows to the upstream receiver ports on
the RS 8000/8600 CMTS modules through the low filter port.