The mode of two optical frequency transfer, for example, ν 0 and ν 0 À f 0 and their
summation on PD with extraction in its load of electrical oscillation with the f 0
frequency can be implemented. We remind that such a mode is called the OEO mode
with the single sideband optical frequency from the optical carrier ν 0 . In this mode,
the ultralow level of oscillation phase noise and high short-term stability of generated frequency are provided owing to interference of two hard-correlated optical
oscillations of the light-sensitive PD area. In OEO, there is a possibility to add on PD
and to obtain in its load of oscillations with the frequency 2f 0 and with more order at
selection of the appropriate optical frequencies in the optical channel. As it is shown
below, utilization of harmonics of the laser modulated oscillations with the frequency ν 0 À 2f 0 expands possibilities of phase noise suppression in OEO.
3.2.1.3 Complex Transfer Function of QWLD
The complex transfer function (TF) (for small signal) of QWLD for the singlefrequency generation mode (with the optical emission frequency ν L ) is determined
from the kinetic equations (considered in Chap. 4) by the ratio: K L ( j2πf,
ν L ) ¼ [P 1L ( j2πf, ν L )/J 1L ( j2πf)] At such limitations, the complex transfer function
of QWLD can be written as:
K L j2πf
ð
Þ¼ω
2
L0 = 1 þ jωC L R d
ð
Þ1 þ jωτ ce
ð
Þ ω
2
L0 À ω
2
À
Á þ jωμÞ
Â
Ã
È
É
ð3:19Þ
K L
j L
0
–10
–20
–30
–40
magnitude (dB)
phase (degrees)
–50
–60
75
50
25
0
–25
–50
–75
–100
0.01
0.1
1
10
0.01
0.1
frequency
10
A 0 = 1.5
10
A 0 = 1. 5
1
1 0
Y(s)
11
12
U(s)
Y(s)
U(s)
Fig. 3.12 The module K L
and argument φ L of QWLD
transfer function for two
different assesses A 0 ¼ J 0L /
J 0Lth of the pumping (bias)
current J 0L above the
threshold value J 0Lth . Values
A 0 ¼ 1.5; 10
98 3 Modulation Methods of Laser Emission in Optoelectronic oscillator (OEO) and OEO. . .