Keysight Technologies N4373D User Manual page 59

Keysight N4373D Lightwave Component Analyzer, User's Guide
The responsivities R
order to have meaning as individual quantities expressed
logarithmically, just as 0 dB represents an S
1.
Consequently source responsivity will be expressed in Watts per
Amp, which in decibels will be related to a conversion efficiency
of 1 W/A. Similarly, receiver conversion efficiency will be
relative to 1 A/W.
20log R
10 s
The individual responsivities can now be expressed individually
in decibels:
 
R dB =
s
 
R dB =
r
This now allows us to express the original equations for
responsivity in logarithmic terms:
 
R dB =
s
 
R dB =
r
Responsivity measurements are now based on the LCA's ability
to accurately measure optical modulation power (DP
modulation current (DI
The measurement of modulation current is derived from the
system characteristic impedance and a measurement of
electrical power.
The measurement of optical modulation power is based on a
"standard" lightwave receiver whose characteristics are
predetermined and known by the LCA.
and R need to be related to some value in
s r
  
R W A
s

R = 20log
----------------------------
r 10

W A
  
R W A
s
20log
----------------------------
10 
W A
  
R A W
r
20log
--------------------------- -
10

A W

P
20log
-------- -
10

I
1

I
2
20log
-------- -
10

P
).
1,2
Measurement Concepts
of unity or gain of
21
  
R A W
r

--------------------------- -

A W
) and
0
57