8–10 GHz, which are useful for a practice, are presented in Figs. 3.8 and 3.9.
Figure 3.8 shows the photo-pictures of experimental OEO models with direct
modulation (Fig. 3.8a) and external MZ modulation (Fig. 3.8b).
Three different OEO structures, studying of which broadens the knowledge of
OEO possibilities as the device intended for generation of microwave and mm-wave
oscillations with ultralow phase noises, are shown in Fig. 3.9.
In the structure in Fig. 3.9a, the second photodetector PD2 is anticipated, and the
laser emission passes to PD2 and detected. This constructive solution allows the
galvanic decoupling of the electrical port, which decreases requirements on the
networks’ matching.
Fig. 3.7 The view of the active QW zone (a) of the quantum-well laser on the base of InGaAsP and
the diagram of energy levels of QWLD (b). On the active QW zone (a), at reduction of its width
down to the value L QW ¼ 1–45 nm, the quantization of the electron and hole energy states occurs
90 3 Modulation Methods of Laser Emission in Optoelectronic oscillator (OEO) and OEO. . .