الفهرس 
Importance of microwave signal, applications and gen- erationOnly 14 pages are availabe for public view
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Abstract
The target of the research in this thesis is to produce a high quality microwave signal using optical techniques. In the literature systems that generate such a signal using optical loops have been suggested. Signals with quality factor of order 108 are produced. Here, in this research a different course is suggested to achieve the same target. An optical filter is adopted to improve the quality of a microwave signal. The quality of such signal has reached 1010, an improvement of two orders of magnitudes over the existing systems.The optical filter consists of a Brillouin/ semiconductor optical amplifier (SOA) ring oscillator fitted with an intensity optical modulator and an optical coupler that feeds an optical detector. The RF signal feeds the modulator while an avalanche photodetector (APD) retrieves it after being fitted through the optical loop. The optical filter linewidth is determined by the Brillouin oscillations which is less than 1 Hz and its free spectral range (FSR) is determined by the length of the optical fiber used in the loop. At a fiber length of 6.6 Km the FSR is 30.3 KHz. The 6 dB bandwidth of the cavity modes is measured to be 780 mHz typical of Brillouin lasers.The gain of the SOA balances out most of the losses in the ring which is mainly due to the RF modulator. The modulated optical signal beats at the APD. The optical loop acts as a cavity filter to the RF signal. A jitter in the cavity resonances due to temperature varaitions is completely eliminated from the output beat signal. The output low frequency noise below 1 KHz is reduced about 10 dB from that of the input. However, there is a 10 dB increase in the phasenoise at the FSR frequency and its harmonics. The setup has been tested with signals generated by different sources and to frequencies up to 10 GHz, the limit of the APD used. Sources with RF linewidth less than the optical FSR produces one output mode with sub-hertz linewidth. For larger linewidth signals more than one RF frequency is produced, separated by the FSR, each showing the Brillouin linewidth.A theoretical study has been conducted also in this work via considering the detailed dynamics of the active optical components of the system, the Brillouin amplifier, the SOA, and the optical modulator. It is found that the quality of this system depends on the operating conditions of these components. The upper frequency limit that can be fitted through this scheme seems to be limited by the carrier lifetime τ_c of the SOA, which is, in our experimental work, 40 ps giving a limit of 25 GHz. In recent literatures τ_c of 10 psec has been obtained which extends the range of our system to 100 GHz. The produced filtering capacity of our system depends on a fine control of the relative gain ratio of the Brillouin amplifier to that of the SOA.