Cisco 7246 - uBR Router, Руководство по установке оборудования

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Cisco uBR7200 Series Universal Broadband Router Hardware Installation Guide
OL-5421-03
Chapter 2 Preparing the Cisco uBR7200 Series Router for Installation
Provisioning the Cable Headend
Note An analog channel modulator with external IF loops is not suitable for use as a digital quadrature
amplitude modulation (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 degraded
performance and possible system failure.
Note
The combiner refers to all cables, amplifiers, and passive components (splitters, directional couplers,
taps, and commercially manufactured combining networks) at the headend or cable distribution center
that connect the Cisco uBR7200 series router to the hybrid fiber-coaxial (HFC) network.
Diplex Filters
For coaxial cabling, diplex filters must be installed in the RF path between the cable interface cards in
the Cisco uBR7200 series universal broadband router and cable interfaces and STBs. Diplex filters
separate the downstream signals from the upstream signals.
Note
For fiber optics, laser transmitters and optical receivers handle the frequency separation of upstream and
downstream. Refer to the
“Receivers” section on page 13 .
High-frequency signals flow in the downstream direction from the Cisco uBR7200 series router to
cable interfaces and STBs. Low-frequency signals flow in the upstream direction from the
cable interfaces to the Cisco uBR7200 series router.
A diplex filter has three ports: low, high, and common. The downstream attaches to the high port because
it runs at high frequency. The upstream attaches to the low port because it runs at a low frequency. The
common port attaches to a splitter attached to one or more cable interfaces and STBs.
In two-way cable networks, the diplex filter takes the upstream and downstream and combines them on
one cable for the cable interface. The downstream output signal from the Cisco uBR7200 series router
runs through the upconverter and then enters the high filter port of the diplex filter. The signal exits the
common port of the filter and is distributed to the cable interfaces. The upstream signal from the cable
modem enters the common port of the diplex filter and flows to the upstream receive ports of the
Cisco uBR7200 series cable interface line cards via the diplex filters low port.
Note
Appendix F, “Manufacturers for Headend Provisioning Requirements,” provides a list of diplex filter
manufacturers and websites for more information.
Receivers
If the upstream channels of your cable plant terminate at the headend over fiber-optic lines, ensure that
you have a receiver allocated for each upstream in your network.