2.6.5 OEO Division According to FOS Topology
Fiber-optical systems on the base of quartz single-mode optical fibers with low
dispersion (t d ¼ 1–3 ps/(nm/km)) on the wavelength of 1.3 μm allows creation of
low-dispersion delay lines for microwave signals with delay time T d ¼ 10–100 μs at
relative time dispersion due to the frequency band of emitted frequencies of the
modulated light source t d /T d ¼ (2–6) Â 10
À7 (nm)
À1
.
This means that the relative delay time for spectral line width on the optical signal
at 30 GHz is t d /T d ¼ (2–6) Â 10
À7 .
The last circumstance gives us a possibility to implement delay lines with the low
phase noise at output basing on the narrowband lasers with the spectral line width
less than 1 MHz.
Application of RF FODL on the base of composite complicate fiber systems for
selection of oscillation types (Fig. 2.5a) is the OEO feature. A rejection character of
the frequency response of such RF FODLs allows a possibility to select the adjacent
oscillation types and to suppress the amplitude of spurious types of oscillations.
Methods of complicate FOSs implementation allow essential reduction of sideband
components of the adjacent oscillation types down to the level À100 to À140 dB/Hz.
A possibility of single-frequency mode in RF microwave range can be provided for
large delay times T dt ¼ 1–50 μs in the fiber system. Application in OEO of
recirculating FOSs with the single or several fibers in the feedback loop
(Fig. 2.5b) is the one utilization of complicate fiber-optical systems in OEO. Such
recirculating RF FODLs has a narrowband PFC of ridged type and can reduce by
several ten times of the geometric length of the optical fiber in OEO. Figure 2.5
introduces the new designation: a wideband amplifier (WBA).
The linear topology of RF FODL differs favorably from the monolithic crystals of
dielectric resonators in RF oscillators in their strengthening characteristic at
destroying percussive impacts. According to own geometrical sizes, they are almost
the same. This strengthening characteristic for the optical fiber constitutes 2000 N/
cm
2 [9] (for monolithic crystals of the leuco-sapphire [31] type with disk diameter
5–8 cm and the 1-cm in thickness, this characteristics is usually one-two orders less)
and it may be one of the governing factors at utilization of the low-noise OEOs in
unmanned orbital stations and unmanned flying vehicles, in military applications,
etc., where percussive and strength characteristics are governing.
The equivalent electric block diagram of OEO with the separate laser (the optical
quantum generator) and the RF part of OEO is shown in Fig. 2.6. The linear part
(LP) of the active element (NE) and RF FODL are also shown in Fig. 2.6, and we can
see the nonlinear current sources of NE (I 1 (U 1 ) and I(U 2 )). To study the frequency,
amplitude, and time functions for OEO, in Chap. 3 of this book we use the
mathematical model of RF FODL, in which we replace RF FODL by the equivalent
two-port with the input conductance, which is equal to input conductance of the MZ
modulator (for version with external modulation of QWLD emission) or to input
conductance of QWLD (for version with direct modulation).
2.6 Integration in Future Optical and Optoelectronic Systems
37
Fiber-optical systems on the base of quartz single-mode optical fibers with low
dispersion (t d ¼ 1–3 ps/(nm/km)) on the wavelength of 1.3 μm allows creation of
low-dispersion delay lines for microwave signals with delay time T d ¼ 10–100 μs at
relative time dispersion due to the frequency band of emitted frequencies of the
modulated light source t d /T d ¼ (2–6) Â 10
À7 (nm)
À1
.
This means that the relative delay time for spectral line width on the optical signal
at 30 GHz is t d /T d ¼ (2–6) Â 10
À7 .
The last circumstance gives us a possibility to implement delay lines with the low
phase noise at output basing on the narrowband lasers with the spectral line width
less than 1 MHz.
Application of RF FODL on the base of composite complicate fiber systems for
selection of oscillation types (Fig. 2.5a) is the OEO feature. A rejection character of
the frequency response of such RF FODLs allows a possibility to select the adjacent
oscillation types and to suppress the amplitude of spurious types of oscillations.
Methods of complicate FOSs implementation allow essential reduction of sideband
components of the adjacent oscillation types down to the level À100 to À140 dB/Hz.
A possibility of single-frequency mode in RF microwave range can be provided for
large delay times T dt ¼ 1–50 μs in the fiber system. Application in OEO of
recirculating FOSs with the single or several fibers in the feedback loop
(Fig. 2.5b) is the one utilization of complicate fiber-optical systems in OEO. Such
recirculating RF FODLs has a narrowband PFC of ridged type and can reduce by
several ten times of the geometric length of the optical fiber in OEO. Figure 2.5
introduces the new designation: a wideband amplifier (WBA).
The linear topology of RF FODL differs favorably from the monolithic crystals of
dielectric resonators in RF oscillators in their strengthening characteristic at
destroying percussive impacts. According to own geometrical sizes, they are almost
the same. This strengthening characteristic for the optical fiber constitutes 2000 N/
cm
2 [9] (for monolithic crystals of the leuco-sapphire [31] type with disk diameter
5–8 cm and the 1-cm in thickness, this characteristics is usually one-two orders less)
and it may be one of the governing factors at utilization of the low-noise OEOs in
unmanned orbital stations and unmanned flying vehicles, in military applications,
etc., where percussive and strength characteristics are governing.
The equivalent electric block diagram of OEO with the separate laser (the optical
quantum generator) and the RF part of OEO is shown in Fig. 2.6. The linear part
(LP) of the active element (NE) and RF FODL are also shown in Fig. 2.6, and we can
see the nonlinear current sources of NE (I 1 (U 1 ) and I(U 2 )). To study the frequency,
amplitude, and time functions for OEO, in Chap. 3 of this book we use the
mathematical model of RF FODL, in which we replace RF FODL by the equivalent
two-port with the input conductance, which is equal to input conductance of the MZ
modulator (for version with external modulation of QWLD emission) or to input
conductance of QWLD (for version with direct modulation).
2.6 Integration in Future Optical and Optoelectronic Systems
37