Cisco ONS 15454 DWDM - Page 502

10-30
Cisco ONS 15454 DWDM Reference Manual, R8.5
78-18343-02
Chapter 10 Network Reference
10.8.1 Gain Tilt Control at the Card Level
Figure 10-20 Flat Gain (Gain Tilt = 0 dB)
If the working gain setpoint of the amplifier is different from Gdesign, the output spectrum begins to
suffer a gain tilt variation.
In order to compensate for the absolute value of the increase of the spectrum tilt, the OPT-BST and
OPT-PRE cards automatically adjust the attenuation of the VOA to maintain a flat power profile at the
output, as shown in Figure 10-21.
Figure 10-21 Effect of VOA Attenuation on Gain Tilt
The VOA attenuator automatic regulation guarantees (within limits) a zero tilt condition in the EDFA
for a wide range of possible gain setpoint values.
-3
-2
0
1
1528 1536 1544 1552 1560
-1
G
design

VOA
att
= 0dB
2
-3
-2
0
1
1528 1536 1544 1552 1560
Wavelength [nm]
Gain Tilt = 0 dB
-1
G
design
VOA
att
= 0 dB
Gain Ripple ~ 2dB
2
134394
Per Channel Power [dB]
-6
-4
-2
0
2
4
1528 1536 1544 1552 1560
Wavelength [nm]
-6
-4
-2
0
2
4
1528 1536 1544 1552 1560
Wavelength [nm]
G< G
design
VOA
att
adjustment
V
O
A
a
t
=
0
d
B
VOA
att
= G
design
-G
Per Channel Power [dB]
134395