Research And Design Of The New Tunable Optoeletronic Oscillator

Microwave photonic technology is widely used in many applications. Among those application, microwave signal source is a necessary device. The spectrum purity, phase noise and stability of the microwave signal will directly affect the system performance of these devices. Therefore, it is particularly important to produce a microwave signal source with high-quality. Because of the high spectrum purity, low phase noise and tunability of the microwave signals produced by the optoelectronic oscillator,optoelectronic oscillator will be more and more used in wireless communications,military radar, optical carrier communication and many other fields.The tunability of the microwave signals produced by the optoelectronic oscillator is mainly theoretically analyzed and experimentally researched in this dissertation. The research and the experiment is under the condition that the spectrum purity of the microwave signal is high and the phase noise of microwave signal is low.The basic principle of optoelectronic oscillator, threshold condition and phase condition of vibration are firstly briefly analyzed. And then setting up an experimental platform to verify that both the single-loop optoelectronic oscillator and the dual-loop optoelectronic oscillator can generate microwave signals. In addition, compared to the single-loop structure, the dual-loop structure can effectively increase the interval of the oscillation mode and improve the Side-Mode Suppression Ratio(SMSR) of the oscillation signal.Secondly, by combining with microwave photonic filter technology and applying three different structure of the tunable microwave photonic filter to the optoelectronic oscillator, three different tunable optoelectronic oscillators are realized: 1, replacing the electric filter in the traditional photoelectric oscillator with a microwave photonic filters based on cross polarization modulation in a highly nonlinear fiber to realize frequency tuning; 2, using multiple wavelength light source produced by using the M-Z interferometer to splice the broadband light source, linear chirp grating and phase modulator together to form a multiple tap microwave photonic filter. The filter is tunable, and its 3 d B bandwidth is very narrow. By incorporating the filter into the optoelectronic oscillator, a frequency-tunable microwave signal is generated; 3, the dual-loop tunable optoelectronic oscillator based on an optical tunable filter is alsoformed by replacing electric filter with microwave photonic filter. The microwave photonic filter consists of a phase modulator and an optical tunable filter.Finally, experimentally studying the three different kinds of tunable optoelectronic oscillator proposed: 1, when adjusting the variable optical delay line, the tunable optoelectronic oscillator based on cross polarization modulation can produce 1.493 GHz,1.811 GHz and 1.864 GHz oscillation signals, and the SMSR of the oscillation frequency of 1.811 GHz is 62 d B. The phase noise is-98.67 d Bc/Hz@10 k Hz and-110.92 d Bc/Hz@100 k Hz. The maximum frequency drift and maximum power drift in half an hour are about 12 k Hz and 1.2 d Bm, respectively; 2, when adjusting the variable optical delay line in M-Z interferometer, the tunable optoelectronic oscillator can produce 0.911 GHz, 1.07 GHz and 1.440 GHz oscillation signals, and the SMSR of the oscillation frequency of 1.07 GHz is 58 d B. The phase noise is-94.77 d Bc/Hz@10 k Hz and-112.60 d Bc/Hz@100 k Hz. The maximum frequency drift and maximum power drift in half an hour are about 10 k Hz and 0.8 d Bm, respectively; 3, for the tunable optoelectronic oscillator based on an optical tunable filter, a contrast experiment between the single-loop tunable structure and the dual-loop tunable structure is made.For a microwave signal of 3.878 GHz, the SMSR of single-loop tunable structure and dual-loop tunable structure are respectively 44 d B and 70 d B. The phase noise is respectively-98.67 d Bc/Hz@10 k Hz and-110.92 d Bc/Hz@100 k Hz,-91.5 d Bc/Hz@10k Hz and-115.9 d Bc/Hz@100 k Hz. In addition, dual-loop tunable structure can produce3.878 GHz, 4.248 GHz, 4.407 GHz, 4.354 GHz and 8.911 GHz oscillation signal. For the oscillation frequency of 3.878 GHz, the maximum frequency drift and maximum power drift in 40 minutes are about 10 k Hz and 0.2 d Bm.