Voltage Output
of CVR
iL(t)
PIC Controller
Equivalent Circuit
50 2 Attenuator
Valued GpIc
Figure 3-38. Time-domain equivalent circuit of the MSE current measurements.
branch. Therefore, the voltage at the input of either fiber-optic transmitter, VFOT(t), is
given by
1 1
VFOT (t)= -GPIcvcvR(t)= -GPIcRCvRiL(t)
2 2
(3-137)
For RCVR = 1.233 mQ, VFOT(t) becomes
VFOT(t) = (0.0006165)GpIciL(t)
The above expression is only valid over the range of frequencies in which the
response of the CVR is constant. The voltage present at the input of the digitizing
oscilloscope, Vscope(t), is the voltage present at the input of the fiber-optic link,
VFOT (t), modified by the link. If the effect of the link is assumed to be a frequency
independent gain or attenuation, of value Glink, then the expression for the voltage at
the input of the oscilloscope is
Vscope(t) = GlinkVFOT (t) = (0.0006165)GPIcGlinkiL(t)
(3-138)