Optical Microwave Signal Generation Methods Based On Multiplication Frequency And Delayed Self-heterodyne

As the performance of electronic equipments is going up continuously, it comes up with higher requires at frequency, spectrum purity and tuning of microwave signal (MS). Compared with conventional electronic approaches, the generation in optical domain offers distinct advantages such as broad bandwidth, low loss, light weight, large tunability and the immunity to electromagnetic interference. This thesis mainly researches about optical MS generation methods. In order to generate a tunable MS with high spectrum purity, a multiplication frequency MS generation method has been studied based on microwave photonic filter (MPF). Another method based on delay self-heterodyne has been researched in order to get a MS with higher frequency. The main contents are as follows.This paper has introduced the principle of two approaches based on external modulation and optical heterodyne technology and analysed the laser typical parameters influence on the signals characters. It is verified that phase noise, frequency fluctuation, and relative intensity noise have a bigger influence.A new approach to generate a frequency multiplied MS is studied and verified experimentally. Based on large signal phase modulation and the dispersion of a single-mode fiber (SMF), the high order of microwave harmonic signal is generated. A tunable single pass-band MPF is used to select a specific harmonic signal by tuning the sliced space of broadband optical source (BOS). In the thesis, we realize the sliced spectrum of BOS based on Mach-Zehnder interferometer (MZI), and analyze the relationship between sliced space and the length of the tunable delay line (TDL). We also realize the tunable MPF and analyze the characters of the center frequency and bandwidth. Based on the theoretic analysis, an experiment system is established. Then, sliced spectrum, filter response and the function of picking up one harmonic signal are observed. At the same time, the harmonic signals at10GHz and15GHz are produced by applying a low frequency signal at5GHz. It can be seen the10dB bandwidth of the signal is about tens of Hz, and the power fluctuation is about1-2dB, which proves the advantages of the method such as narrow line-width, tuning easily, high spectrum purity and good suppressing the other harmonic signals. This method can avoid the bias drifting of intensity modulator and the using of tunable optical filters and generate a multiplication frequency MS with good tunability and high spectrum purity.Another approach based on dual wavelengths of tunable laser (TLD) and delayed heterodyne is studied, which can avoid using radio frequency (RF) signal and realize high frequency and power signal output. The MS is detected in the coherence time by the two wavelength sources which come from the same resonant cavity period and are delayed by MZI. The frequency depends on the amplitude difference of the driving signal. Therefore, the wavelength range with current and the pulse frequency range are observed when the waves change steadily. Then, it studied on theory and experiment. According to the experiment, it is found that the TLD with narrow line-width and fast-tuning is indispensable for generating high quality MS. However, because of the limits of devices in the lab, the thesis only worked on the theoretic analysis and measurement on the influent factors.