Cisco UBR7225VXR Hardware Installation Manual page 94

Connecting and Configuring the Upstream
This "X-level" test point measurement will be different for every fiber node in the HFC network until
you adjust the attenuation on the upstream. You must adjust the attenuation so that this measurement is
the same on every fiber node. If you change a receiver or a transmitter at the fiber node, or if you unplug
a connector and plug it back in, you must recheck this amplitude measurement.
three distribution network "X-level" test points connected to the same upstream port are all calibrated to
+10 dBmV using different attenuators.
Figure 4-24 Calibrating Multiple "X-level" Test Points Connected to One Upstream Port
Cisco
uBR7225VXR
Upstream
0 dBmV
+10 dBmV
3 dB
attenuator
+10 dBmV
3 dB
attenuator
4-way
splitter
+10 dBmV
3 dB
attenuator
40 dB
attenuator
Figure 4-25
upstream ports are all calibrated to +10 dBmV using different attenuators.
Cisco uBR7225VXR Universal Broadband Router Hardware Installation Guide
4-20
Downstream
+13 dBmV
3 dB
X
attenuator
+18 dBmV
8 dB
X
attenuator
+31 dBmV
21 dB
X
attenuator
Diplex filter
L H
C
Cable
modem
shows how three distribution network "X-level" test points connected to the three different
Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Reverse optical
Optical
transmitter
receiver Fiber-optic
+17 dBmV
cable
Reverse optical
Optical
transmitter
receiver Fiber-optic
+17 dBmV
cable
Optical Reverse optical
transmitter
receiver Fiber-optic
+17 dBmV
cable
To downstream
forward test point
on laser transmitter
Figure 4-24
Cable
modems
+31 dBmV
Distribution
+48 dBmV
network
Modem transmit levels
+58 dBmV
Distribution
network +42 dBmV
Modem transmit levels
+50 dBmV
Distribution
network
+46 dBmV
+49 dBmV
Modem transmit levels
shows how
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