laser diode by means of variation of the pumping current; in the solid-state lasers
with optical pumping—by means of variation of the central frequency of the external
or internal narrowband optical filter.
Figure 7.28 shows experimental (solid lines) and theoretical (dotted line) functions of the frequency f(Δx) (а), f(Δν/ν) (b) and the amplitude U(Δx)/U max (c), U(Δν/
ν)/U max (d) for OEO with the differential RF FODL with the directional coupler of
the Х-type.
Experimental and theoretical investigations of OEO with differential RF FODL
with the directional coupler of the Х-type reveals the oscillating character of its
frequency and amplitude functions (Fig. 7.28). These experimental functions are
well agreed with the developed mathematical model and the analytical functions. We
should note such important property of OEO that the slope of the frequency
variations f(Δx) (Fig. 7.28a) is S f ¼ Δf/Δx ¼ 0.015 kHz/μm, the slope of frequency
variations of the laser optical frequency f(Δν/ν) (Fig. 7.28b) is S f ¼ Δf/(Δν/
ν) ¼ 0.05 kHz/(1 relative unit).
Another peculiarity of OEO with the combined differential RF FODL with the
coupler of Х-type is the variation of RF frequency of OEO at variation of the QWLD
optical frequency. Because the transformation slope of the optical frequency at
different choice of the optical frequency of QWLD is different owing to the “cosine”
function of the optical frequency (Eq. 7.53), the slope of radio frequency retuning at
variation of the optical frequency is different at the different choice of the central
frequency of QWLD generation. This described property of OEO with the coupler of
Х-type, which plays the role here of the optical frequency discriminator, which is
recommended to use in OEO systems for registration of the laser emission spectrum
as well as in systems of the secretive (masking) optical control of the radio frequency
of the remote oscillator in OEO with RF FODL.
Thus, in OEO with RF FODL with couplers of Y and Х types, we can choose
several approaches for the control of the generation frequency. The control owing to
variation of excitation coefficients of optical channels or the FOS of different
geometrical length, by means of variations of the refraction index of the optical
material in couplers and due to variations of the laser optical frequency.
7.5 Parametric Frequency Instability of OEO with RF
FODL at Temperature Impact of the Single Optical
Fiber
The parametric frequency instability of OEO with respect of temperature at large
delays in the optical fiber (more than 0.5 μs, the geometrical length of FOS is 100 m)
is mainly determined be temperature variations of the optical fiber parameters.
7.5 Parametric Frequency Instability of OEO with RF FODL at Temperature Impact of. . . 427
with optical pumping—by means of variation of the central frequency of the external
or internal narrowband optical filter.
Figure 7.28 shows experimental (solid lines) and theoretical (dotted line) functions of the frequency f(Δx) (а), f(Δν/ν) (b) and the amplitude U(Δx)/U max (c), U(Δν/
ν)/U max (d) for OEO with the differential RF FODL with the directional coupler of
the Х-type.
Experimental and theoretical investigations of OEO with differential RF FODL
with the directional coupler of the Х-type reveals the oscillating character of its
frequency and amplitude functions (Fig. 7.28). These experimental functions are
well agreed with the developed mathematical model and the analytical functions. We
should note such important property of OEO that the slope of the frequency
variations f(Δx) (Fig. 7.28a) is S f ¼ Δf/Δx ¼ 0.015 kHz/μm, the slope of frequency
variations of the laser optical frequency f(Δν/ν) (Fig. 7.28b) is S f ¼ Δf/(Δν/
ν) ¼ 0.05 kHz/(1 relative unit).
Another peculiarity of OEO with the combined differential RF FODL with the
coupler of Х-type is the variation of RF frequency of OEO at variation of the QWLD
optical frequency. Because the transformation slope of the optical frequency at
different choice of the optical frequency of QWLD is different owing to the “cosine”
function of the optical frequency (Eq. 7.53), the slope of radio frequency retuning at
variation of the optical frequency is different at the different choice of the central
frequency of QWLD generation. This described property of OEO with the coupler of
Х-type, which plays the role here of the optical frequency discriminator, which is
recommended to use in OEO systems for registration of the laser emission spectrum
as well as in systems of the secretive (masking) optical control of the radio frequency
of the remote oscillator in OEO with RF FODL.
Thus, in OEO with RF FODL with couplers of Y and Х types, we can choose
several approaches for the control of the generation frequency. The control owing to
variation of excitation coefficients of optical channels or the FOS of different
geometrical length, by means of variations of the refraction index of the optical
material in couplers and due to variations of the laser optical frequency.
7.5 Parametric Frequency Instability of OEO with RF
FODL at Temperature Impact of the Single Optical
Fiber
The parametric frequency instability of OEO with respect of temperature at large
delays in the optical fiber (more than 0.5 μs, the geometrical length of FOS is 100 m)
is mainly determined be temperature variations of the optical fiber parameters.
7.5 Parametric Frequency Instability of OEO with RF FODL at Temperature Impact of. . . 427