Study On Microwave Photonic Generator Used In Radio Over Fiber System

Microwave photonics,which brings together the worlds of microwave,photonics,optoelectronics and radiofrequency engineering,has become a new technical field.It is considered as a prospective subject,who can find many applications in both military and civilian areas,including cellular,wireless,and satellite communications,distributed antenna systems,imaging and radar system.Its research effect covers microwave photonic generator,high frequency optoelectronic devices,photonic signal processing techniques and radio over fiber(RoF)system.Under the supports of National Nature Science Foundation of China,this dissertation is devoted to investigate the new prototypes of microwave photonic generator for RoF system,by theory,simulation and experiment.The main innovative research efforts are sumarized as follows:1.A novel structure of frequency-octupling millimeter-wave photonic generator based on improved feed-forward modulation(IFFM)technique has been proposed and verified experimentally,which is capable of generating frequency stabilized millimeter-waves by employing two incoherent optical sources.Meanwhile,an inner-sideband locking technique is illustrated by theory and experiments.Combining the technology with IFFM technology,the frequency tuning characteristic of the generator can be greatly improved.The frequency of the generated signal involves microwave,millimeter wave and terahertz wave band,which is useful to extend the scope of application of the millimeter wave photonic generator.2.Two novel structures of millimeter-wave photonic generator with higher frequency multiplication factor have been proposed and verified.Both two proposals employ IFFM technique.They can achieve frequency 16-tupling and 32-tupling stabilized millimeter wave generation,respectively,by employing two incoherent optical sources.Comparing the two schemes,it is found that there is a positive correlation between the enhancement of frequency multiplication factor of optical carrier suppression(OCS)modulation process and the improvement of frequency multiplication factor of generator.Which means the improvement of overall frequency multiplication factor of scheme,can be achieved by increasing the frequency multiplication factor of OCS modulation process.At the same time,the change of overall frequency multiplier factor caused by changing the frequency doubling factor of the OCS modulation process does not change the basic characteristics of IFFM technology.The enhancement of frequency multiplication factor has a positive effect on the maximum output frequency,tunable range and performance of millimeter-wave photonic generator.3.A novel structure of microwave photonic generator with high frequency multiplier factor and reduced power fluctuation has been proposed and verified,which is capable of achieving frequency 20-tupling radio frequency signal generation with anti-power fluctuation characteristic.With the help of these beneficial characteristics,the devices cost and power penalty can be effectively reduced and the signal receiving sensitivity can be enhanced,which is very helpful for improving the stability,sensitivity and performance of RoF system.4.A novel structure of frequency tunable microwave photonic generator with high frequency multiplier factor and reduced power fluctuation has been proposed and verified,which is capable of achieving frequency 36-tupling radio frequency signal generation with anti-power fluctuation and frequency tuning characteristics.With the help of these beneficial characteristics,the proposed generator is able to support high reliable and high frequency(over 100GHz)communication with relatively low device cost and transmission power penalty and achieve flexible signal conversion without changing the system structure,which is useful for improving the stability,flexibility,adaptability,secrecy and performance of RoF system.5.A novel structure of frequency-quadrupled Nyquist pulse photonic generator based on rectangular optical frequency comb(ROFC)has been proposed and verified experimentally.The generator is able to support frequency-quadrupled ROFC generation with relatively low modulation index and achieve Nyquist pulse generation with a repetition rate that is four times of local oscillator frequency.The proposal provides a good solution for obtaining high speed pulse signals from low speed components.Moreover,being benefited from the filter free structure,the high-flexibility of the generated Nyquist pulse can be realized,which is helpful for reducing the device cost and complexity of generator and expanding its application.6.A novel structure of multi-function microwave photonic generator with tunable multiplication factors has been proposed and verified.By controlling the polarization direction,the amplitudes of optical sidebands can be flexibly controlled,which provides an opportunity to convert the multiplication factor between 2 and 6 without changing the modulation index of built-in modulator.Benefiting from the generator's multi-functional characteristics,RoF system based on the proposal is able to support data transfer switched on two bands with a constant frequency local oscillator.This is beneficial to the improvement of security of RoF system and the extension of its application.7.A novel structure of multi-function microwave/pulse photonic generator has been proposed and verified,which is capable of achieving frequency tripling microwave signal and Nyquist pulse generation.The proposal provides a new direction for the study of multi-function microwave photonic generator,which is a prototype of microwave/pulse photonic generator.Benefiting from the filter free structure,the generator is able to support the frequency tunable microwave signal generation and achieve Nyquist pulse generation with flexible repetition frequency,which is helpful for improving adaptability and performance of microwave/-pulse photonic generator.