Anritsu MS9740B - Procedures

5.6 Measuring Laser Diode Modules
5-45
5
Measurement Functions
SNR (/ *.*nm) means Signal to Noise Ratio per Noise BW.
SNR (/ *.*nm) is calculated using the following equation:








′
=
)(
log10
,
sig
LinS
N
L
SNR
l
(dB-nm)
N’(λ
sig
): Linear value (W) of noise level normalized by
Noise BW
N ( l
sig
) a
)(
sig
N l
′
= · NBW (W/nm)
ActRes ( l
sig
)
ActRes(λ
sig
): Actual resolution (nm) at optical signal
wavelength
NBW: Noise BW
Note:
With the SNR measurement, L
s,Lin
in the SNR calculation formula
is the value subtracting the noise level, regardless of the Signal
Level settings of Signal Parameter.
5.6.4 Procedures
To measure laser diode module
1. Input the optical signal in the MS9740B.
2. Set the wavelength, resolution, and level scale.
3. Press
Single
to start the measurement.
4. When the name of the
F7
horizontal key is not
Application
, press
F8
,
and then press
F7
.
5. Press
f6 LD Module Test
to display the measurement result display
field.
6. Press
f1 Signal Parameter
.
7. Specify the wavelength and level measurement method using the
arrow keys or rotary knob.
8. Press
f7 Set
to update the value in the measurement result display
field.
9. Press
f2 Noise Parameter
.
10. Specify the noise measurement method using the arrow keys or
rotary knob.
11. Press
f7 Set
to update the value in the measurement result display
field.
12. Press
f3 Noise Position
.
13. Set the difference in wavelength between the wavelength where the
noise level is measured and the wavelength of the optical signal. For
the measurement location of noise level, refer to Figure 5.6.2-3.