Cisco ONS 15454 DWDM - Flat Gain (Gain Tilt = 0 Db)

18-30
Cisco ONS 15454 DWDM Installation and Operations Guide, R6.0
August 2005
Chapter 18 Network Reference
18.8.1 Gain Tilt Control at the Card Level
Figure 18-14 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/OPT-BST-E and OPT-PRE cards automatically adjust the attenuation of the VOA to maintain
a flat power profile at the output, as shown in Figure 18-15.
Figure 18-15 Effect of VOA Attenuation on Gain Tilt
The VOA attenuator automatic regulation guarantees (within limits) a “zero tilt” condition in the EDFA
amplifier 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