once mentioned in Chaps. 3–6 that the phase noise suppression only owing to the
increase of the geometrical length of FOS is not the solution of the problem of the
phase noise reduction at offsets F ¼ 1 kHz. The other more effective methods of the
phase noise suppression are: the statistical averaging at photodetection of the optical
harmonics, the equalization in power excitation in the MZ optical channels, the
application of the high-coherent in time and in space QWLD with the spectral line
width of 10 kHz and less.
6.5.13 The Approximate Formula for the Coefficient K
2
ΓPN
In this section, we analyze the main part of the expression (6.58) for K
2
ΓPN for
utilization in engineering calculations. Assuming that OEO MZ operates and small
exceeds above the excitation threshold (with the small excitation reserve) and at
Y 00
P 0L
¼
y M 1þFT EF
½
Š
P 0L K FOLD
j
j % 1, for expression (6.58) for K
2
ΓPN the following transformations
are true:
0.05
1
0.500
0.100
0.050
0.010
0.005
0.001
0.10
0.50
(a)
(b)
1
1 0
5
K 2
*PN
K 2
*PN2 ,(FT
FOS ), G
12 K 2
*PN2 ,(FT
FOS ) [a.u]
delay time FT FOS [a.u]
G 12 K 2
*PN
0.05
10
1
0.100
0.010
0.001
100
10 –1
0.10
0.50 1
10
5
K 2
*PN
K 2
*PN ,(FT
FOS ), G
12 K 2
*PN ,(FT
FOS )
Offset frequency, FT FOS
G 12 ·K 2
*PN
Fig. 6.26 Functions of the
suppression coefficient of
the phase noise in OEO MZ
K
2
ΓPN FT FOS
ð
Þand
G 12 K
2
ΓPN FT FOS
ð
Þat P 0L /
Y 00 ¼ 1.01 for σ U ¼ 10.0;
for T c ¼ 10; at
G 12 ¼ {1 À exp [ÀFT FOS /
(FT c )]}. K
2
ΓPN FT FOS
ð
Þis
calculated on the formula
(6.77) (a). Functions of the
suppression coefficient
square K
2
ΓFM FT FOS
ð
Þof the
phase noise in OEO MZ and
G 12 Á K
2
ΓFM FT FOS
ð
Þat P 0L /
Y 00 ¼ 1.01 for σ U ¼ 1.0 at
T c ¼ 10T FOS for
G 12 ¼ {1 À exp [ÀT FOS /
(T c )]}. Function were
calculated by the formula
(6.77) (b)
340
6 Operation Analysis of Optoelectronic oscillator (OEO) with External. . .