Anritsu MS9740B - Calculation Method

5.1 Measuring DFB-LD (Distributed Feedback Laser Diode)
5-5
5
Measurement Functions
5.1.2 Calculation Method
● σ
This is calculated using the following formula:
2
2
c
n
nn
B
B
－λ
λ
σ＝
∑
∑
×
i
ii
n
nn
BBB
BBB
B
B
c
＋･･･＋
λ＋･･･λ＋λ
＝
λ
＝λ
21
2211
∑
∑
×
where, Bn and λn (n = 1, 2, 3 ….i) is calculated as level and wavelength
at the point with a level more than a slice level down from the peak.
● Mode Offset, Stop Band, Center Offset
These are calculated using the following formulae:
Mode Offset = λ
side
– λ
max
Stop Band = λ
right
– λ
left
Center Offset =
2
leftright
axm
ll
l
+
−
where, λmax is the wavelength at the maximum peak, λ
left
is the
wavelength at the left side of the maximum peak, λ
right
is the wavelength
at the right side of the maximum peak, and λ
side
is the side mode
wavelength.
However, λ
side
is the side mode selected from the side mode settings, 2nd
Peak, Left or Right.
Figure 5.1.2-1 Position of Peak Wavelength and Side Mode
l
left
l
Max
l
right