various Q-factors of the RF filter: 1—the RRF Q-factor is 450, 2—the Q factor is
560, 3—the Q-factor is 900.
The experimental sample of the low-noise differential laser oscillator of the
microwave range with operating frequency of 8.2 GHz contains of the QWLD
with the line width not more than 1 MHz. QWLD and the photodetector have the
specific units for bias currents regulators. QWLD has the additional unit for temperature regulation.
From presented functions, we see that growth of the RF filter Q-factor leads to
reduction of PSD of the phase noise, and for the RFF Q-factor of 1000 in OEO with
the MZ modulator, the power spectral density of the phase noise on the level
À120 dBm/Hz is obtained for the offset 1–10 kHz. At that, we can note that without
introduction of special measures, the level of spurious harmonics is from À80 to
À30 dBm/Hz and even higher. The frequency difference between harmonics is
determined by the geometrical length.
Measures for spurious harmonic level reduction, when using the differential delay
line, to the level À100 to À120 dBm/Hz are used with the directional couplers.
Fig. 8.15 Experimental samples of OEO with RF FODL operating in the microwave range with the
optical fiber length of 4464 m (а) and 100 m (b). The experimental sample of OEO with QWLD for
direct modulation operating in the microwave range of 8.2 GHz with optical fiber length of 4464 m
(view from above) (c)
488
8 Experimental Investigations and Practical Circuits of Optoelectronic. . .
560, 3—the Q-factor is 900.
The experimental sample of the low-noise differential laser oscillator of the
microwave range with operating frequency of 8.2 GHz contains of the QWLD
with the line width not more than 1 MHz. QWLD and the photodetector have the
specific units for bias currents regulators. QWLD has the additional unit for temperature regulation.
From presented functions, we see that growth of the RF filter Q-factor leads to
reduction of PSD of the phase noise, and for the RFF Q-factor of 1000 in OEO with
the MZ modulator, the power spectral density of the phase noise on the level
À120 dBm/Hz is obtained for the offset 1–10 kHz. At that, we can note that without
introduction of special measures, the level of spurious harmonics is from À80 to
À30 dBm/Hz and even higher. The frequency difference between harmonics is
determined by the geometrical length.
Measures for spurious harmonic level reduction, when using the differential delay
line, to the level À100 to À120 dBm/Hz are used with the directional couplers.
Fig. 8.15 Experimental samples of OEO with RF FODL operating in the microwave range with the
optical fiber length of 4464 m (а) and 100 m (b). The experimental sample of OEO with QWLD for
direct modulation operating in the microwave range of 8.2 GHz with optical fiber length of 4464 m
(view from above) (c)
488
8 Experimental Investigations and Practical Circuits of Optoelectronic. . .