process of FOS manufacture owing to doping in the quartz thread of boron and
germanium elements and their oxides and by selection of mutually compensating
dopes in the thread and FOS envelope.
The variant of the temperature compensation is the utilization in OEO of differential RF FODL. One of methods of compensation of OEO frequency offsets due to
temperature is the application of the control systems with external stable quartz
oscillators or the quantum-frequency standards on cesium vapors.
Figure 7.33 shows the dependences of the OEO generation frequency at variations of OF temperature: (а) OF without the polymer envelope (see d); (b) OF with
the polymer (length is 300 m) (see e); (с) the OF cable with the double polymer
envelope (see f).
The analysis of frequency-temperature functions (Fig. 7.31) gives a possibility to
conclude that the presence of the OF polymer envelope leads to the hysteresis
character of functions. These original results in measurement of the frequencytemperature functions allow the correct selection and optimization of RF FODL
construction for OEO, which are exposed by the temperature impact.
7.5.5 Brief Conclusions
The analysis of the frequency control in OEO with differential RF FODL on the base
of two optical fibers of different lengths connected by their inputs by directional
couplers of Y- or Х-type is performed, and the long-term frequency instability in
OEO is studied. The following conclusions are made.
The utilization of selection on the optical frequency in FOS with DC of Y-type for
the frequency control is possible at presence of the additional optical frequency
spatial selector, for instance, of the optical dispersive crystal mounted in the break
Fig. 7.32 The structure of the temperature-compensated OEO. OR1, OR2 are optical resonators, M
is the electro-optical modulator (Patent belongs to authors [24])
436
7 Optoelectronic oscillator (OEO) as the Time and Spatial Correlator of Random. . .
germanium elements and their oxides and by selection of mutually compensating
dopes in the thread and FOS envelope.
The variant of the temperature compensation is the utilization in OEO of differential RF FODL. One of methods of compensation of OEO frequency offsets due to
temperature is the application of the control systems with external stable quartz
oscillators or the quantum-frequency standards on cesium vapors.
Figure 7.33 shows the dependences of the OEO generation frequency at variations of OF temperature: (а) OF without the polymer envelope (see d); (b) OF with
the polymer (length is 300 m) (see e); (с) the OF cable with the double polymer
envelope (see f).
The analysis of frequency-temperature functions (Fig. 7.31) gives a possibility to
conclude that the presence of the OF polymer envelope leads to the hysteresis
character of functions. These original results in measurement of the frequencytemperature functions allow the correct selection and optimization of RF FODL
construction for OEO, which are exposed by the temperature impact.
7.5.5 Brief Conclusions
The analysis of the frequency control in OEO with differential RF FODL on the base
of two optical fibers of different lengths connected by their inputs by directional
couplers of Y- or Х-type is performed, and the long-term frequency instability in
OEO is studied. The following conclusions are made.
The utilization of selection on the optical frequency in FOS with DC of Y-type for
the frequency control is possible at presence of the additional optical frequency
spatial selector, for instance, of the optical dispersive crystal mounted in the break
Fig. 7.32 The structure of the temperature-compensated OEO. OR1, OR2 are optical resonators, M
is the electro-optical modulator (Patent belongs to authors [24])
436
7 Optoelectronic oscillator (OEO) as the Time and Spatial Correlator of Random. . .