On the base of data obtained, we may make a conclusion about necessity of bias
current regulation for the light-emitting diodes and laser diodes used in OEO with
RF FODL to values 10
À4 to 10
À3 . Measured average slopes S f of the function f(I bias )
(at the same offsets |I bias À I thr | from the threshold value I thr ) in areas of current
variations upper and lower of the threshold value, are approximately equal for OEO
with RF FODL and the laser diode are S f ¼ Δf/ΔI bias ¼ 15 kHz/mA.
A phenomenon of polarity change of the laser diode time constant slope and the S f
slope of the function of f(I bias ) for OEO with the laser diode gives a possibility to
select correctly the bias operating currents of the laser diode and the amplitude of the
modulation signal as well as to optimize constructions of the laser diode modulator,
Fig. 8.25 Experimental spectra of output optical emission of LD1 (а) and at output of the optical
filter (formed by LD2) (b) in the OEO with the frequency of 10 GHz. Experimental spectra of output
optical emission of LD1 (с) and at output of the optical filter (formed by LD2) (d) in the OEO with
the frequency of 30 GHz
8.6 Conclusions
503