Anritsu MS9740B - How to Set the Signal Measurement Method

5.6 Measuring Laser Diode Modules
5-35
5
Measurement Functions
5.6.1 How to Set the Signal Measurement Method
In the Signal Parameter dialog box, set the level range and
wavelength/level detection method.
● SMSR Parameter
This selects the detection method for the Side Mode.
2nd Peak: Peak with next highest level after maximum
peak becomes side mode
Left: Peak to left adjacent side of maximum peak
becomes side mode
Right: Peal to right adjacent side of maximum peak
becomes side mode
● Kσ
This sets constant for standard deviation σ
K = 2.35 is equivalent to 3 dB down, and K = 6.07 is equivalent to 20
dB down.
● ndB Width
This specifies the cut level used for spectrum width measurement. The
cut level is an attenuator from the peak level.
● Search Resolution
This sets the level resolution (dB) to define the side mode.
Peak P1 in the following diagram has ripple P4 of Δl4 dB. If this ripple
is evaluated as a side mode, the SMSR is not measured correctly. In
this case, if the level resolution is set to a larger value than Δl4 dB, the
P4 ripple is not detected and SMSR can be measured.
Figure 5.6.1-1 Example of Waveform where 2nd Peak Not Measured
Correctly
P
1
P
2
P
3
P
4
∆
l
1
∆
l
2
∆
l
3
∆
l
4