Figure 6.28c shows the transfer function of the closed loop OEO MZ KFN(F)
versus the offset F (from the generation frequency f 0 of OEO MZ) at different delay
values T FOS in FOS and the power P OL of the QWLD optical emission.
The functions of the suppression coefficients K
2
2ΓPN ¼ KFN presented in
Fig. 6.28b, c permit to estimate the suppression degree of PSD of the phase noise
in OEO. The tenfold suppression of PSD of the phase noise can be realized in OEO
MZ in the offset region at the delay in FOS T FOS ¼ 3 Á 10
À5 s and the power of
QWLD optical emission of P OL ¼ 30 mW.
From the analysis of Figs. 6.27 and 6.28, it follows that achievement of small
values of the power spectral density of the phase noise of RF oscillations in OEO MZ
on the offset frequency F ¼ 1 kHz less than S(F) ¼ À120 dB/Hz is provided by the
significant growth of laser power P 0L (for example, more than 20 mW), by the
reduction of the laser line bandwidth Δv (for instance, less than 10 kHz) and by
increase of the delay time T FOS of optical oscillations in the FOS (or the geometrical
length of FOS till several kilometers).
6.6 Analog Modeling of OEO MZ
In previous section of this chapter, we investigated of OEO MZ on the linear models,
which allowed to study of OEO MZ at presence of the complicate fluctuation impact.
But, this linear model does not take into consideration in full measure the nonlinear
properties of systems. The question is raised about investigation performing on the
base of the analog modeling of OEO MZ structure with utilization of specific
software packets with the aim, on the one hand, of checking of results obtained by
the other approaches, and on the other hand, to execute investigations being beyond
application areas of these methods. Such investigations are, for example, studying of
transients in OEO MZ, and are also an examination of FOS dispersion influence on
the oscillation spectrum in OEO MZ, on PSD of the phase and amplitude noise
taking into consideration the laser fluctuations in the OEO structure. At that, the
analog model allowed laser spectrum formation, which is close to the Lorentz form
on the frequency function.
In view of above-told, the goal of the next part of Chap. 6 is to provide the analog
modeling of OEO MZ with the help of specific mathematical packet, to obtain the
time-functions of PSD and transients in OEO MZ at its switching-on basing on the
analog model in Fig. 6.29a.
6.6.1 Description of the Analog Model
We construct the model of OEO MZ and solve the problem on input noise impacts.
The model is based on imitation of the real functioning of the system. The laser
348
6 Operation Analysis of Optoelectronic oscillator (OEO) with External. . .
versus the offset F (from the generation frequency f 0 of OEO MZ) at different delay
values T FOS in FOS and the power P OL of the QWLD optical emission.
The functions of the suppression coefficients K
2
2ΓPN ¼ KFN presented in
Fig. 6.28b, c permit to estimate the suppression degree of PSD of the phase noise
in OEO. The tenfold suppression of PSD of the phase noise can be realized in OEO
MZ in the offset region at the delay in FOS T FOS ¼ 3 Á 10
À5 s and the power of
QWLD optical emission of P OL ¼ 30 mW.
From the analysis of Figs. 6.27 and 6.28, it follows that achievement of small
values of the power spectral density of the phase noise of RF oscillations in OEO MZ
on the offset frequency F ¼ 1 kHz less than S(F) ¼ À120 dB/Hz is provided by the
significant growth of laser power P 0L (for example, more than 20 mW), by the
reduction of the laser line bandwidth Δv (for instance, less than 10 kHz) and by
increase of the delay time T FOS of optical oscillations in the FOS (or the geometrical
length of FOS till several kilometers).
6.6 Analog Modeling of OEO MZ
In previous section of this chapter, we investigated of OEO MZ on the linear models,
which allowed to study of OEO MZ at presence of the complicate fluctuation impact.
But, this linear model does not take into consideration in full measure the nonlinear
properties of systems. The question is raised about investigation performing on the
base of the analog modeling of OEO MZ structure with utilization of specific
software packets with the aim, on the one hand, of checking of results obtained by
the other approaches, and on the other hand, to execute investigations being beyond
application areas of these methods. Such investigations are, for example, studying of
transients in OEO MZ, and are also an examination of FOS dispersion influence on
the oscillation spectrum in OEO MZ, on PSD of the phase and amplitude noise
taking into consideration the laser fluctuations in the OEO structure. At that, the
analog model allowed laser spectrum formation, which is close to the Lorentz form
on the frequency function.
In view of above-told, the goal of the next part of Chap. 6 is to provide the analog
modeling of OEO MZ with the help of specific mathematical packet, to obtain the
time-functions of PSD and transients in OEO MZ at its switching-on basing on the
analog model in Fig. 6.29a.
6.6.1 Description of the Analog Model
We construct the model of OEO MZ and solve the problem on input noise impacts.
The model is based on imitation of the real functioning of the system. The laser
348
6 Operation Analysis of Optoelectronic oscillator (OEO) with External. . .