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Appendix 2 Data Calculation Algorithms for Spectrum Widths
App-6
In the case of three or more valid mode peaks.
1
• Set the levels (LOG) of three or more valid mode peaks to LG1, LG2 • • • LGn in order
from the left. Set the level of the mode peak at the highest level to LGp.
• Obtain
in the following manner:
λ
1
• In the case of |LGp-LG1| is threshold value (THRESH1[dB]) or less
Set the wavelength of the LG1 mode peak to
• In the case of |LGp-LG1| is larger than threshold value (THRESH1[dB])
i Obtain the leftmost mode peak with |LGp-THRESH1| or more.
ii Use a straight line to connect the mode peak obtained in (i) with the mode peak
on the left of (i) and also at the highest level.
iii Set the point, where the line of |LGp-THRESH1| and the straight line (envelope)
cross, to
.
λ
1
• Obtain
in the following manner:
λ
2
• In the case of |LGp-LGn| is threshold value (THRESH1[dB]) or less.
Set the wavelength of the LG1 mode peak to
• In the case of |LGp-LGn| is larger than threshold value (THRESH1[dB])
i Obtain the rightmost mode peak with |LGp-THRESH1| or more.
ii Use a straight line to connect the mode peak obtained in (i) with the mode peak
on the right of (i) and also at the highest level.
iii Set the point, where the line of |LGp-THRESH1| and the straight line (envelope)
cross, to
.
λ
2
• Use the following equations, which incorporate multiplication by the multiplying factor
K for
and
, to obtain new
λ
λ
1
2
'C = (
+
)/2
λ
λ
λ
2
1
= K × (
-
'C) +
λ
λ
λ
λ
1
1
= K × (
-
'C) +
λ
λ
λ
λ
2
2
• Obtain the spectrum width from the following equation.
Δ
=
-
λ
λ
λ
2
1
• Obtain the center wavelength
C = (
+
)/2
λ
λ
λ
2
1
Threshold
Value
2
and
.
λ
λ
1
2
'C
'C
C from the following equation.
λ
.
λ
1
.
λ
2
IM 735302-01E
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