10-29
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 10-19 Effect of Gain Ripple and Gain Tilt on Amplifier Output Power
Gain ripple and gain tilt are defined as follows:
• Gain ripple is random and depends on the spectral shape of the amplifier optical components.
• Gain tilt is systematic and depends on the gain setpoint (Gstp) of the optical amplifier, which is a
mathematical function F(Gstp) that relates to the internal amplifier design.
Gain tilt is the only contribution to the power spectrum disequalization that can be compensated at the
card level. A VOA internal to the amplifier can be used to compensate for gain tilt.
An optical spectrum analyzer (OSA) is used to acquire the output power spectrum of an amplifier. The
OSA shows the peak-to-peak difference between the maximum and minimum power levels, and takes
into account the contributions of both gain tilt and gain ripple.
Note Peak-to-peak power acquisition using an OSA cannot be used to measure the gain tilt, because gain
ripple itself is a component of the actual measurement.
10.8.1 Gain Tilt Control at the Card Level
The OPT-BST and OPT-PRE amplifier cards have a flat output (gain tilt = 0 dB) for only a specific gain
value (Gdesign), based on the internal optical design (see Figure 10-20).
-4
-2
0
2
4
1530.3 1560.6
Wavelength [nm]
Gain Tilt
Amplifier Output Spectrum
1550
Gain Ripple
Per-Channel power [dB]
134393
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