Research On Optoelectronic Oscillator And Its Applications In Sensing

Sensing and measurement technology play an important role in modern scientific research and industrial development.With the rapid development of optoelectronic technology,more and more optoelectronic sensors are employed in practical systems operating as a key element.It is of great significance to develop a new measurement method in order to meet the rigorous requirement of measurement field.The optoelectronic oscillator(OEO)employs an optical-electrical feedback structure with large delay to construct a loop with ultrahigh quality factor.It can generate microwave of ultralow phase noise and its phase noise does not deteriorate with the increasement of its frequency,which results in a quite low jitter even at microwave and millimeterwave band.Meanwhile,the OEO frequency is sensitive to its loop length variation,the higher the oscillation frequency,the larger the sensitivity.As a result,the OEO shows great potential in high sensitivity and high resolution sensing applications.In this thesis,the theoretical models of the OEO are reviewed and the phase noise performance of the OEO is deeply investigated.Then OEO stabilization based on heterodyne phase-locking and intermediate frequency filtering are proposed and investigated.After that,the structures,theory and applications of the OEO in temperature,strain,pressure and vibration sensing are demonstrated.The main innovations in this thesis are as follows:1.Phase noise distribution characteristic of an OEO is analyzed by combining the classic Yao-Maleki and Leeson models.The relationship of intensity noise to phase noise conversion within the radio frequency amplifier is experimentally investigated.Phase noise design approach of the OEO is also proposed according to its distribution.2.Two OEO structures for low phase noise microwave generation are proposed.One is the heterodyne phase-locking OEO.It is simplified to a low order phase-locked-loop(PLL).Therefore,the stability problem that may encounter in a high-order one is avoided.The other is the intermediate frequency filtering(IFF)based OEO structure within which the influence of the local oscillator's phase noise to the OEO output is investigated.The IFF OEO's phase noise is reduced by using a long loop in the experiment.3.The IFF OEO structure is employed in temperature sensing,the error resulting from the random initial oscillation frequency is eliminated.A phase tracking based discrimination approach is proposed inspired by the heterodyne idea,and the dynamic range of the sensor is not limitated by the free spectrum range(FSR)any more.A strain sensing experiment is designd to prove the feasibility of this method.Finally,a dual-loop dual-frequency OEO based pressure sensor is proposed and the error caused by temperature drifting is effectively removed.4.A phase-shifted carrier modulation based OEO with high strain sensitivity by cascading a dual-output Mach-Zenhder modulator and a fiber interforemeter is proposed for vibration sensing.The relationship between the phase noise and the minimum detectable phase is deduced and the dynamic range of the sensor is investigated as well.The experiment results reveal the advantage of OEO in small vibration signal sensing.