Wideband Frequency Tunable Optoelectronic Oscillator

Optical generation of microwave signals, typically optoelectronic oscillator(OEO), can generate microwave signals with much lower single pass band (SSB)phase noise, and large frequency tunability, which have wide applications in opticalsignal processing, military radar systems, communication, inter-satellite links, andbio-imaging for identifying cancers. This thesis was aimed to theoretically andexperimentally study on an OEO based on multi-wavelength laser source, which haswide tunable frequency range and low phase noise.The parameters of the typical optical link including gain, noise figure, anddynamic range were analyzed at first. On the basis of the link and the primary OEOtheory, wideband frequency tunable OEOs based on microwave photonic filter (MPF)operated by broadband optical source and laser array were proposed, respectively.The theoretical model, numerical simulation as well as the experimental studies ofthe tunable MPF and OEO based on laser array were studied, respectively. Finally,systematic OEO experiments based on broadband optical source were investigated.Besides, the microwave signals with tunable frequency range of12GHz and themode-hopping suppression were realized by cascading the IIR filter.The main content of this paper is organized as followed:(1) Typical methods of optically generated microwave signals were introducedand compared, and an emphasis on the OEOs was presented. Then weanalyzed the noise figure resulting in phase noise of microwave signals, and the factors to influence gain,1dB compression dynamic range and spur freedynamic range in the simple optical link or EDFA gained optical link.Experiments were carried out to verify the theory and simulation.(2) The gain of the open loop and the phase noise spectrum of conditional OEOwere analyzed. MPFs based on broadband optical source and laser array wereinvestigated. OEO experiments based laser array, group delay and opticaltrue delay were operated.(3) The single bandpass MPF based on variable optical carrier time shifting,especially the decay effect of dispersion slope on the amplitude response ofthe MPF was investigated. And then the OEO experiment was made byclosing the loop. In order to improve the stability of the oscillating signals,further experiments were made by cascading different loop length anddifferent coupling ratio of Sagnac loop.