Anritsu MS9740B - Page 31

1.1 Introduction of Optical Spectrum Analyzer
1-3
1
Outline
The scale unit is as follows.
Horizontal axis
Wavelength
nm (nanometer) 1 nm = 10
-9
m
Frequency
THz (terahertz) 1 THz = 10
12
Hz
Vertical axis
Linear scale,
normal value
state
W (watt),
mW (milliwatt) 1 mW = 10
-3
W,
µ
W (microwatt) 1
µ
W = 10
-6
W,
nW (nanowatt) 1 nW = 10
-9
W,
pW (picowatto) 1 pW = 10
-12
W
Linear scale,
relative value
state
% (percentage)
Logarithm scale,
normal value
state
dBm
Logarithm scale,
relative value
state
dB (decibel)
The frequency indication of horizontal axis is compatible with the marker
location and analysis result.
dBm is an abbreviation for the power ratio in dB of the measured power
referenced to 1 mW. The conversion formula of P
1
(mW) and P
2
(dBm) is as
follows.
P
2
= 10•log (P
1
)
dB is the logarithm of the ratio. The conversion formula of R
1
(%) and R
2
(dB) is as follows.
R
2
= 10•log (
R
1
100
)
The optical wavelength varies with the Index of Refraction n. The
relationship between the wavelength in a vacuum λv and in air λa is as
follows.
λa =
λv
n
The horizontal axis can be switched to display wavelength either in a
vacuum or in air.
For more information, refer to 4.1 “Wavelength-related Settings”.