the conclusion is deduced that at light guide excitation from the laser diode, the
effective signal delay (passed through RF FODL) varies approximately by 10–15%
from the bias current value and relative spatial location of the exciting light guide
and the laser diode.
Utilization of the selector of optical modes in OEO in input of the exciting light
guide is necessary since small variations of the signal delay in RF FODL formed by
the laser diode, the fiber-optical system, and the phase detector, lead to 10–15%variations of generation frequency in OEO. Variations of the OEO generation
frequency are caused by small bias current drift in the laser diode and are different
for various angular deviations of the optical axis of fiber optical system from the
optical axis of the laser diode.
Fig. 8.24 The general view of the electrical voltage indicator with OEO and the piezoelectric
sensor S and optical connectors Y-OC1, Y-OC2 (a). The inductive magneto-gorge sensor of AC
electric current (b) and general view of the electric current sensor with the optical cable (c)
502
8 Experimental Investigations and Practical Circuits of Optoelectronic. . .