The sixth chapter describes the calculation approach of the nonsymmetrical
optical channel included in the OEO structure. The beginning of Chap. 7 has
something in common with Chap. 4 in the description style because we perform in
it the investigation of the waveguide section. We showed that methods of the OEO
phase noisesuppression are not exhausted by development of the high-coherent
lasers, wideband modulators and photodetectors (with the modulation band 10–
60 GHz), but widen with utilization of the spatial methods of laser emission
selection. At that, we can use of different filters and optical Fourier transforms
[10], which are known from the adaptive optics and are successfully suppressed of
the optical carrier, noises and extracting the useful signal.
To the one of advantage of Chap. 7 we can attribute the fact that we considered
methods of the phase and frequency automatic control systems, which are capable to
decrease the OEO phase noise by 10–15 dBm/Hz.
The large section in Chap. 7 is devoted to experimental investigations of the longterm frequency stability in OEO and the parametric frequency stability of OEO from
temperature of the optical fiber. Described results of temperature researches within
the limits of 0–120
С allow development of the thermal-stabilized optical fiber for
FODL in OEO, as well as the patented OEO system with two optical resonators,
which is stable to temperature variations. On the base of the model of optical mode
coupling, we explain of the observed in the experiments the oscillating character of
the temperature dependence in the multi-mode optical fibers and in systems of
coupled optical fibers.
The description of several patents developed by authors is presented in Chaps. 7
and 8: the OEO sensor with division of the frequency measurement and the phase
difference measurement, OEO with differential delay line with application of Y- and
X-fiber-optical couplers. We think that frequency and amplitude functions in OEO at
variations of the excitation conditions of optical fibers in different branches will be
interesting for readers. The special interest is represented of the oscillating functions
of the OEO frequency with the differential FODL with the X-coupler.
Original results of experimental amplitude, frequency and phase responses in
OEO of the microwave and mm-wave ranges are described in Chap. 8. We would
like to specially emphasize of the hysteresis frequency functions in OEO with the
“spasmodic transition” at the single-frequency generation. Frequency jumps are
caused by the fulfillment of the excitation conditions for many types of oscillations
at increase of the geometrical length of the optical fiber, and the hysteresis character
is defined by the inertial nonlinear characteristic of OEO nonlinear elements.
We would like to note that conducted tedious laser investigations, which are
included in the OEO structure, permits to reveal the interesting physical phenomena.
The bifurcation of the laser directional pattern is one of such phenomena. Theoretical
explanation of this phenomenon is presented in Chap. 7, at the examination of
nonsymmetric active and passive waveguide optical structures. The phenomenon
of the slope polarity sign change in the frequency response of OEO at variation of the
pumping current can be attributed to another new physical phenomenon, which are
discussed in Chaps. 7 and 8.
510
Conclusion
optical channel included in the OEO structure. The beginning of Chap. 7 has
something in common with Chap. 4 in the description style because we perform in
it the investigation of the waveguide section. We showed that methods of the OEO
phase noisesuppression are not exhausted by development of the high-coherent
lasers, wideband modulators and photodetectors (with the modulation band 10–
60 GHz), but widen with utilization of the spatial methods of laser emission
selection. At that, we can use of different filters and optical Fourier transforms
[10], which are known from the adaptive optics and are successfully suppressed of
the optical carrier, noises and extracting the useful signal.
To the one of advantage of Chap. 7 we can attribute the fact that we considered
methods of the phase and frequency automatic control systems, which are capable to
decrease the OEO phase noise by 10–15 dBm/Hz.
The large section in Chap. 7 is devoted to experimental investigations of the longterm frequency stability in OEO and the parametric frequency stability of OEO from
temperature of the optical fiber. Described results of temperature researches within
the limits of 0–120
С allow development of the thermal-stabilized optical fiber for
FODL in OEO, as well as the patented OEO system with two optical resonators,
which is stable to temperature variations. On the base of the model of optical mode
coupling, we explain of the observed in the experiments the oscillating character of
the temperature dependence in the multi-mode optical fibers and in systems of
coupled optical fibers.
The description of several patents developed by authors is presented in Chaps. 7
and 8: the OEO sensor with division of the frequency measurement and the phase
difference measurement, OEO with differential delay line with application of Y- and
X-fiber-optical couplers. We think that frequency and amplitude functions in OEO at
variations of the excitation conditions of optical fibers in different branches will be
interesting for readers. The special interest is represented of the oscillating functions
of the OEO frequency with the differential FODL with the X-coupler.
Original results of experimental amplitude, frequency and phase responses in
OEO of the microwave and mm-wave ranges are described in Chap. 8. We would
like to specially emphasize of the hysteresis frequency functions in OEO with the
“spasmodic transition” at the single-frequency generation. Frequency jumps are
caused by the fulfillment of the excitation conditions for many types of oscillations
at increase of the geometrical length of the optical fiber, and the hysteresis character
is defined by the inertial nonlinear characteristic of OEO nonlinear elements.
We would like to note that conducted tedious laser investigations, which are
included in the OEO structure, permits to reveal the interesting physical phenomena.
The bifurcation of the laser directional pattern is one of such phenomena. Theoretical
explanation of this phenomenon is presented in Chap. 7, at the examination of
nonsymmetric active and passive waveguide optical structures. The phenomenon
of the slope polarity sign change in the frequency response of OEO at variation of the
pumping current can be attributed to another new physical phenomenon, which are
discussed in Chaps. 7 and 8.
510
Conclusion