At utilization in RF FODL of the special single-mode optical fiber with the length
4.6 km, the OEO frequency instability of 10
À6 /degree is obtained in the experiment
on the OEO frequency 8.2 GHz. The accuracy of the temperature measurement is
0.1
С, and the accuracy of the frequency measurement is 10
À6 .
The hysteresis character of the temperature frequency functions (Fig. 7.31) is
concerned to the original result of theoretical and experimental investigations, which
can be explained not only by the variation of the light guide refraction index, but by
the temperature volumetric extensions of the double protective polymer envelope.
The decrease of weight coefficients till the values of 10
À2 is possible if to decrease
the thickness of the polymer envelope till 1–2 μm (or not to form of the polymer
envelope of FOS at the technological cycle of the FOS manufacture). In this case, the
temperature frequency instability in OEO is as in usual quartz systems, i.e., it is
determined by the refraction index of the quartz light-guiding thread: 10
À5 to 10
À6 .
The temperature stabilization of FOS till the values ΔT OF /T OF ¼ 10
À3 leads to the
OEO frequency instability Δf/f ¼ 10
À8 .
On the base of the analysis of theoretical experimental results of this phenomenon, authors developed and patented the structure of temperature-compensated OEO
(Fig. 7.32) [24]. We recommend providing the decrease of the OEO temperature
instability using the thermal compensation methods of the FOS0 optical fiber. By
selection of weight coefficients a thr and a pol of the quartz thread and the envelope, we
achieve the decrease of the temperature coefficient of the refraction index of the FOS
thread till the values Δn OF /(n OF ΔT OF ) ¼ 10
À6 to 10
À7 , for instance, during the
Fig. 7.31 Experimental functions of the frequency (а) and phase differences (b) of OEO at
temperature variation in the air thermostat; the light guide with the length of 100 m is without the
polymer envelope. Figure (b) shows the dependence of the phase difference for different positions
of the optical selector: 0
, À5
, +5
, À7.5
with regard to the optical axis of the optical fiber in its
output
7.5 Parametric Frequency Instability of OEO with RF FODL at Temperature Impact of. . . 435
4.6 km, the OEO frequency instability of 10
À6 /degree is obtained in the experiment
on the OEO frequency 8.2 GHz. The accuracy of the temperature measurement is
0.1
С, and the accuracy of the frequency measurement is 10
À6 .
The hysteresis character of the temperature frequency functions (Fig. 7.31) is
concerned to the original result of theoretical and experimental investigations, which
can be explained not only by the variation of the light guide refraction index, but by
the temperature volumetric extensions of the double protective polymer envelope.
The decrease of weight coefficients till the values of 10
À2 is possible if to decrease
the thickness of the polymer envelope till 1–2 μm (or not to form of the polymer
envelope of FOS at the technological cycle of the FOS manufacture). In this case, the
temperature frequency instability in OEO is as in usual quartz systems, i.e., it is
determined by the refraction index of the quartz light-guiding thread: 10
À5 to 10
À6 .
The temperature stabilization of FOS till the values ΔT OF /T OF ¼ 10
À3 leads to the
OEO frequency instability Δf/f ¼ 10
À8 .
On the base of the analysis of theoretical experimental results of this phenomenon, authors developed and patented the structure of temperature-compensated OEO
(Fig. 7.32) [24]. We recommend providing the decrease of the OEO temperature
instability using the thermal compensation methods of the FOS0 optical fiber. By
selection of weight coefficients a thr and a pol of the quartz thread and the envelope, we
achieve the decrease of the temperature coefficient of the refraction index of the FOS
thread till the values Δn OF /(n OF ΔT OF ) ¼ 10
À6 to 10
À7 , for instance, during the
Fig. 7.31 Experimental functions of the frequency (а) and phase differences (b) of OEO at
temperature variation in the air thermostat; the light guide with the length of 100 m is without the
polymer envelope. Figure (b) shows the dependence of the phase difference for different positions
of the optical selector: 0
, À5
, +5
, À7.5
with regard to the optical axis of the optical fiber in its
output
7.5 Parametric Frequency Instability of OEO with RF FODL at Temperature Impact of. . . 435