Anritsu BERTWave MP2100B, Operation Manual, Page: 49 / 382

1.5 Technical Terms
1-19
1
Outline
Extinction Ratio
The extinction ratio is the ratio of 1 Level and 0 Level; it is used for
evaluating optical signal waveforms.
The extinction ratio is calculated by the following formula.
Extinction Ratio = 10log
10
{(L
1
– L
D
)/(L
0
– L
D
)} (dB)
L
1
: 1 Level (mW) 
L
0
: 0 Level (mW)
L
D
: Level without optical input (mW)
L
0
L
1
–
L
D
L
1
L
D
L
0
–
L
D
Figure 1.5-8 Extinction Ratio Measurement Level
Duty Cycle Distortion
The duty cycle distortion (DCD) is found from the following equation:
DCD = (t
2
– t
1
)/Bp × 100 (%)
Where,
t
1
 Time at crossing point between Eye Width 50% level and rising
waveform
t
2
: Time at crossing point between Eye Width 50% level and falling
waveform
Bp: Bit cycle
t
1
t
2 Bp
50%
0%
100%
Eye Amplitude
t
2
–
t
1
Figure 1.5-9 Duty Cycle Distortion