Cisco Systems UBR7225VXR specifications Optical receiver

Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend

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. Figure 4-24shows how 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

4-way splitter

Upstream 0 dBmV

3 dB

attenuator

3 dB

attenuator

3 dB

attenuator

40 dB

Downstream

+10 dBmV
	X	3 dB
		attenuator

+10 dBmV

8 dB

X attenuator

+10 dBmV

21 dB

X attenuator

Diplex filter

Optical receiver

+13 dBmV

Optical receiver

+18 dBmV

Optical receiver

+31 dBmV

	Reverse optical		Cable
			modems
Fiber-optic transmitter			+31 dBmV
cable	+17 dBmV	Distribution	+48 dBmV
		network
	Reverse optical	Modem transmit levels
Fiber-optic transmitter			+58 dBmV
cable	+17 dBmV	Distribution
		network	+42 dBmV
	Reverse optical	Modem transmit levels
Fiber-optic transmitter			+50 dBmV
cable	+17 dBmV	Distribution
		network	+46 dBmV
			+49 dBmV
		Modem transmit levels

attenuator

L H

C

Cable modem

To downstream forward test point on laser transmitter

271677

Figure 4-25shows how three distribution network “X-level” test points connected to the three different upstream ports are all calibrated to +10 dBmV using different attenuators.

	Cisco uBR7225VXR Universal Broadband Router Hardware Installation Guide
4-20	OL-17309-02