Agilent Technologies 83487A User Manual page 76

Reference
Measuring High Power Waveforms
Table 5-1. Recommended Attenuation for Signals > –10 dBm with 100% Overshoot
Average Power
µ
dBm
W
100 –10.0
125 –9.0
200 –7.0
316 –5.0
400 –4.0
500 –3.0
800 –1.0
1000 0.0
In order to find out if your device under test may be exceeding the input
power requirements for the Agilent 83487A, first measure the average power
with the internal power meter, and then measure the peak power on the eye
diagram. If the average power exceeds –10 dBm (100 µW), you may need to
attenuate the signal (this assumes there is 100% overshoot present). Insert
the recommended attenuation from
power again. If you are using a laboratory attenuator, then you will have a dig-
ital readout of the attenuation. If you are using a simple fixed attenuator, then
the attenuation value will be the difference between the average power read-
ing with and without the attenuator.
The Agilent 83480A allows the attenuation to be accounted for and removed
from the measurement. Press the Optical Channel Setup key (above the optical
connector), and then the External scale softkey. Enter in the value of the attenu-
ator, and the instrument will then read the true signal level prior to attenua-
tion. You can then go back and measure the peak power on the eye diagram
again. If this measurement is the same as the original peak measurement with-
out the attenuator, then you do not have compression and you are in a safe
measurement power zone with or without the attenuator. If the peak measure-
5-8
100% Overshoot Attenuation
Peak Power (100%)
µ
dBm
W
400 –4.0
500 –3.0
800 –1.0
1265 1.0
1600 2.0
2000 3.0
3200 5.1
4000 6.0
Table 5-1, and then measure the average
Attenuator Net Input
Avg.
dB
dBm
0.0 –10.0
1.0 –10.0
3.0 –10.0
5.0 –10.0
6.0 –10.0
7.0 –10.0
9.1 –10.0
10.0 –10.0
Peak
dBm
–4.0
–4.0
–4.0
–4.0
–4.0
–4.0
–4.0
–4.0