Agilent Technologies 86038A User Manual page 268

Troubleshooting and Upgrades
If you see errors in Group Delay measurements but no error is visible in
Gain/Loss
N O TE
268
This is most likely the result of Gain Stage switching. The ODA is based on
a Performance Network Analyzer which uses Step Gain values to keep the
input signal in the most linear region of the 16 bit ADC. The Step Gain is
selected based on the power level detected by the Network Analyzer.
While the Network Analyzer has corrections for the Gain/Loss
measurements, no such corrections exist for phase. As the input power
changes and causes a Gain Stage switch, a 200 fs jump in Group Delay
may be observed (50f s is typical). The TLS power level can be lowered to
eliminate this artifact. Alternatively, the TLS power level can be raised to
move the artifact out of the region of interest.
page 105 for more information.
For more information, refer to Chapter 8, "Specifications and Regulatory
Information."
Solving Measurement Problems
Refer to "Laser Setup" on
Agilent 86038A Optical Dispersion Analyzer, Third Edition