System Level Gain Tilt Control - Cisco ONS 15454 DWDM Installation And Operation Manual

Chapter 18 Network Reference
Table 18-22
as well as the maximum (worst case) values of gain tilt and gain ripple expected in the specific gain
range.
Table 18-22
Amplifier
Card Type
OPT-BST/
OPT-BST-E
OPT-PRE
If the "operating" gain value is outside of the range shown in
introduces a tilt contribution for which the card itself cannot directly compensate. This condition is
managed in different ways, depending the amplifier card type:
•
•

18.8.2 System Level Gain Tilt Control

System level gain tilt control for OPT-PRE cards is achievable with two main scenarios:
•
•
18.8.2.1 System Gain Tilt Compensation Without ROADM Nodes
When an OPT-PRE card along a specific line direction (West to East or East to West) is working outside
the "flat output" gain range (G > 21 dB), the unregulated tilt is compensated for in spans not facing
ROADM nodes by configuring an equal but opposite tilt on one or more of the amplifiers in the
downstream direction. The number of downstream amplifiers involved depends on the amount of tilt
compensation needed and the gain setpoint of the amplifiers that are involved. See
August 2005
shows the "flat output" gain range limits for the OPT-BST/OPT-BST-E and OPT-PRE cards,
Flat Output Gain Range Limits
Flat Output
Gain Range
G < 20 dB
G < 21 dB
OPT-BST/OPT-BST-E. The OPT-BST/OPT-BST-E amplifier is, by card design, not allowed to work
outside the "zero tilt" range. The MetroPlanner tool validates network designs using the
OPT-BST/OPT-BST-E amplifier card only when the gain is less than or equal to 20 dB.
OPT-PRE. The MetroPlanner tool allows network designs even if the operating gain value is equal
to or greater than 21 dB. In this case, a system-level tilt compensation strategy is adopted by the
DWDM system. A more detailed explanation is given in the following section.
Without a reconfigurable optical add-drop multiplexer (ROADM) node
With a ROADM node
Gain Tilt Gain Ripple
(Maximum) (Maximum)
0.5 dB 1.5 dB
0.5 dB 1.5 dB
Cisco ONS 15454 DWDM Installation and Operations Guide, R6.0
18.8.2 System Level Gain Tilt Control
Table 18-22, the EDFA amplifier
Figure 18-16.
18-31