Anritsu MS9740B - Page 179

5.5 Measuring WDM (Wavelength Division Multiplexed) Signals
5-29
5
Measurement Functions
Figure 5.5.4-2 Fitting Curve and Noise Level when Area Type is User
Specify
6. SNR is calculated using the following equation.








=
)(
log
10
,
sig
LinS
N
L
SNR
l
(dB)
where, L
SLin
is linear value (W) of level at signal and N(λsig) is linear
value (W) of noise level at optical signal wavelength.
When Level Detection Type is set to Point, the optical signal level is
calculated by the following formula:
)()
(
,
sigsigLins
NP
L ll −
=
(W)
P(λsig): linear value (W) of level at optical signal wavelength
When Level Detection Type is set to ΣPower, the optical signal level is
calculated by the following formula:
)(
*
1
*)}()({
1
,
iesActRSampl
Span
NiPL
n
i
sigLinS
a
l
−
−=
∑
=
(W)
n: Data count in the range of Signal Span
Span: Span (nm)
Sampl: Sampling point
P(i): ith data level (W)
ActRes(i): ith data Actual Resolution
α: Equipment dependent power correction coefficient
Ps
1
+Pn
1
Pn
1
Ps
2
+Pn
2
Ps
3
+Pn
3
Pn
2
Pn
3
Wl
1
Wl
2
Wl
3
Level
Wavelength
(nm)
Wl
1
,Wl
2
,Wl
3
:Signal wavelength
Ps
1
,Ps
2
,Ps
3
:Signal level Pn
1
,Pn
2
,Pn
3
:Noise level