App-5
IM AQ6376-01EN
Appendix
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App
Index
In the case of two valid mode peaks.
λ
1
λ
2
Threshold Value
• Set the levels (LOG) of the two valid mode peaks to LG1 and LG2 in order from the
left.
• Obtain
λ
1
and
λ
2
in the following manner.
• In the case of |LG2-LG1| is threshold value (THRESH1[dB]) or less.
λ
becomes
λ
1
and
λ
2
from the left in order.
• In the case of |LG2-LG1| is larger than threshold value (THRESH1[dB])
Connect two valid mode peaks with a straight line (envelope).
In the case of LG1>LG2, set the wavelength for the left mode peak to
λ
1
. Set the
wavelength of the point, where the line below the peak level by the threshold value
(THRESH[dB]) and the straight line (envelope) cross, to
λ
2
.
In the case of LG1<LG2, set the wavelength for the right mode peak
λ
2
. Set the
wavelength of the point, where the line below the peak level by the threshold value
(THRESH[dB]) and the straight line (envelope) cross, to
λ
1
.
• Use the following equations, which incorporate multiplication by the multiplying factor
K for
λ
1
and
λ
2
, to obtain new
λ
1
and
λ
2
.
λ
'C = (
λ
2
+
λ
1
)/2
λ
1
= K × (
λ
1
-
λ
'C) +
λ
'C
λ
2
= K × (
λ
2
-
λ
'C) +
λ
'C
• Obtain the spectrum width from the following equation.
Δ
λ
=
λ
2
-
λ
1
• Obtain the center wavelength
λ
C from the following equation
λ
C = (
λ
2
+
λ
1
)/2
Appendix 2 Data Calculation Algorithms for Spectrum Widths
