the frequency detuning range equals to 2(10
À3 to 10
À4 ), relatively, at FOS length of
6 m and 60 m. This range depends on the ratio of the delay time of the microwave
signal envelope in QWLD to the delay time of the microwave signal in FOS.
The slope of OEO generation frequency function versus the pumping current in
the microwave values (8–12 GHz) at small exceeds of the pumping current above the
threshold value (1.5–3) is about (10–30) ps/(maÁT FOS ), while at large exceeds (5–8),
it is about (1–3) ps/(maÁT FOS ).
On the base of the analysis of OEO generation frequency upon the pumping
current at utilization of QWLD in the microwave range and the laser diode in RF
range, we proved theoretically a possibility to control the generation frequency by
the DC pumping current of the laser diode. The perspective of QWLD application as
the modulated light source in stabilized tuned OEO with RF FODL in microwave
and mm-wave ranges is also proved.
7.4 Frequency Control in OEO with RF FODL with Two
Optical Fibers
7.4.1 The Structure of OEO DM with RF FODL with Two
Optical Fibers
For the combined FOSs, which are formed by two optical fibers of different length,
the expression for the controlled resistance of OEO with the differential RF FODL
(Fig. 7.21) can be written as:
K FODL jω
ð Þ ¼ R jω
ð Þ ¼ _
D jω
ð Þ
 exp Àα n L 0 þ L 1
ð
Þ
½
A exp Àjω T 0FOS þ T 1FOS
ð
Þ
½
þ B exp Àjω T 0FOS þ T 2FOS
ð
Þ
½
1 þ j ω À ω F
ð
Þ T F
,
ð7:42Þ
where A and B are excitation coefficients of FOS1 and FOS2, relatively, and they are
equal: A ¼ P 1 /(P 1 + P 2 ), B ¼ P 2 /(P 1 + P 2 ); P 1 , P 2 are introduced absolute values of
the light power in FOS1 and FOS2, relatively; L 0 , L 1 , L 2 are geometric lengths of
fiber FOS0, FOS1, FOS2, relatively; T 0FOS , T 1FOS , T 2FOS are delay times of the
optical signal in FOS0, FOS1, FOS2, relatively, are equal: T 0FOS ¼ L 0 Á N(ν)/c,
T 1FOS ¼ L 1 Á N(ν)/c, T 2FOS ¼ L 2 Á N(ν)/c, where с is the light speed in the free space,
v is the optical frequency, N(ν) is the refraction index of the light-guiding thread, _
D jω
ð Þ
is the complex coefficient, which is determined by QWLD and PD parameters.
Under following conditions:
• Noninertial AE in NA
• Linearity of the modulated light source (LD), PD, and FOS
7.4 Frequency Control in OEO with RF FODL with Two Optical Fibers
409
À3 to 10
À4 ), relatively, at FOS length of
6 m and 60 m. This range depends on the ratio of the delay time of the microwave
signal envelope in QWLD to the delay time of the microwave signal in FOS.
The slope of OEO generation frequency function versus the pumping current in
the microwave values (8–12 GHz) at small exceeds of the pumping current above the
threshold value (1.5–3) is about (10–30) ps/(maÁT FOS ), while at large exceeds (5–8),
it is about (1–3) ps/(maÁT FOS ).
On the base of the analysis of OEO generation frequency upon the pumping
current at utilization of QWLD in the microwave range and the laser diode in RF
range, we proved theoretically a possibility to control the generation frequency by
the DC pumping current of the laser diode. The perspective of QWLD application as
the modulated light source in stabilized tuned OEO with RF FODL in microwave
and mm-wave ranges is also proved.
7.4 Frequency Control in OEO with RF FODL with Two
Optical Fibers
7.4.1 The Structure of OEO DM with RF FODL with Two
Optical Fibers
For the combined FOSs, which are formed by two optical fibers of different length,
the expression for the controlled resistance of OEO with the differential RF FODL
(Fig. 7.21) can be written as:
K FODL jω
ð Þ ¼ R jω
ð Þ ¼ _
D jω
ð Þ
 exp Àα n L 0 þ L 1
ð
Þ
½
A exp Àjω T 0FOS þ T 1FOS
ð
Þ
½
þ B exp Àjω T 0FOS þ T 2FOS
ð
Þ
½
1 þ j ω À ω F
ð
Þ T F
,
ð7:42Þ
where A and B are excitation coefficients of FOS1 and FOS2, relatively, and they are
equal: A ¼ P 1 /(P 1 + P 2 ), B ¼ P 2 /(P 1 + P 2 ); P 1 , P 2 are introduced absolute values of
the light power in FOS1 and FOS2, relatively; L 0 , L 1 , L 2 are geometric lengths of
fiber FOS0, FOS1, FOS2, relatively; T 0FOS , T 1FOS , T 2FOS are delay times of the
optical signal in FOS0, FOS1, FOS2, relatively, are equal: T 0FOS ¼ L 0 Á N(ν)/c,
T 1FOS ¼ L 1 Á N(ν)/c, T 2FOS ¼ L 2 Á N(ν)/c, where с is the light speed in the free space,
v is the optical frequency, N(ν) is the refraction index of the light-guiding thread, _
D jω
ð Þ
is the complex coefficient, which is determined by QWLD and PD parameters.
Under following conditions:
• Noninertial AE in NA
• Linearity of the modulated light source (LD), PD, and FOS
7.4 Frequency Control in OEO with RF FODL with Two Optical Fibers
409