5.5.10 The Oscillation Spectrum at Closed Feedback Loop
At the closed switch Sw, in the diagram shown Figs. 5.10 and 5.11, at fulfillment of
OEO excitation conditions, the amplified electrical oscillation passes to the electrical
input of the MZ modulator from the output of the photodetector. We would like to
note that this oscillation is delayed by the time T FOS with respect to the laser
oscillation, which arrives to the photodetector. As shown in Chap. 6 of the present
book, in this case, the radio-frequency spectrum in the PD output S RFL (F) is
determined by the formula:
random quantity h
0.02
0.02
10 -5
10 -10
10 -15
0.001
0.010
0.005
0.100
0.050
0.010
0.005
0.050
0.100
5 × 10 –4
1
0.2
0.2
(a)
–0.010
–0.005
0.005
0.010
random quantity h
(b)
probability distribution
p
02 (h)
probability distribution
p
02 (h)
s
2
x = 2
s
2
x = 2
Fig. 5.20 The distribution
density p 1 (ξ 0PN ) (Eq. 4.166)
in the multiplier input (a)
and p 02 η
ð Þ ¼ p 2 η
ð Þ Á 2πσ
2
ξ Á
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi
1 À exp À
2ΔTM
Tc
h
i
r
in
the multiplier output of the
double-channel correlator
(b) (at opened or closed
feedback loop) for different
values of 2(ΔT M + T FOS )/
T c ¼ 1 at different values of
σ
2
ξ ¼ 2, 0:2, 0:02. Plots are
presented in the logarithm
(a) and linear (b) scales
278
5 Optoelectronic oscillator (OEO) Differential Equations as the Laser System with. . .