Research On Optoelectronic Oscillators And Its Application

Microwave sources with low phase noise and high-frequency stability are the key components of modern communication,radar,navigation,and electronic measurement systems.An optoelectronic oscillator(OEO)with advantages of low phase,high-frequency stability,and broad frequency tunability is a technology of photonics generating microwave signals that convert optical energy into microwave energy through an optoelectronic feedback loop.The OEO breaks through the bottleneck of the electric generation of microwave signals and is of considerable significance to improve the performance of electronic systems.Thus,the OEO has become a research hotspot in microwave photonics.In this dissertation,we theoretically and experimentally study the OEO,including its basic theory,testing method,new structure,and applications.The main research contents and innovation points are as follows:1.Research on the basic theory of OEOsThe basic theory of an injection-locked OEO is studied.By deducing the phase difference differential equation in the time domain,the theoretical model is established,the locking conditions are clarified,the frequency pulling phenomenon is explained,and the influencing factors of phase noise characteristics are analyzed.The theoretical analysis results are verified by experiments,which provide a theoretical basis for the injected-locked OEO research and development.2.Research on the phase noise measurement of an OEOA dual phonic-delay line cross-correlation method for the phase noise measurement of a microwave signal is proposed based on wavelength division multiplexing(WDM).The several-kilometer long fiber delay line is co-used by the two measurement channels through WDM based on a traditional dual phonic-delay line cross-correlation method.Thus,the system complexity and the difficulty of dual-channel delay matching are reduced.The experiment system was established.Measurement ranges from 4 to 11 GHz,and a phase noise floor of-152.6d Bc/Hz@10k Hz at 10 GHz was implemented.The proposed method provides a reliable way of measuring the phase noise of wide-band and low-phase-noise microwave sources.A phase noise measurement scheme based on the fusion of a dual-loop OEO and a dual phonic-delay line cross-correlation phase noise measurement system is proposed.The dual-loop OEO,where the two feedback loops share the long fiber delay line,was experimentally demonstrated,and a side-mode suppression ratio(SMSR)of 82.4 d B was implemented.The phase noise measurement system was also established.The OEO phase noise was measured to be-122 d Bc/Hz@10k Hz at 10.664 GHz by the proposed phase noise measurement method,consistent with the measurement result of a commercial phase noise measurement instrument.The technical difficulty of the phase noise measurement of an OEO is reduced.3.Research on new structure OEOsAn OEO based on injection locking and time-delay compensation is proposed.The time-delay compensation system compensates for the loop delay caused by temperature in real-time to maintain the oscillation frequency within the locked range of the injection-locking OEO,and the stable single-mode oscillation is implemented.In the demonstration experiment,the frequency stability of ±0.1 ppb at 10.664 GHz was implemented when the temperature fluctuated between 22-31 ? within 1000 s.An SMSR of 78 d B and a frequency tuning resolution of 10 Hz was also realized.An enhanced SMSR and improved frequency stability are implemented in the proposed OEO.A frequency tunable OEO based on parity-time(PT)symmetry is proposed.The PT symmetry is implemented based on a silicon integrated microdisk resonator(MDR)with reciprocity.Thanks to the strong mode selection ability of PT-symmetry,the filter bandwidth requirement in the OEO is reduced.The frequency tunability of the PT-symmetric OEO is implemented due to the thermal tunability of the MDR.In the demonstration experiment,a PT-symmetric OEO with a tuning range from 2 to 12 GHz and an output power higher than 15 d Bm were implemented.The phase noise was measured to be-117.3d Bc/Hz@10k Hz when the loop length was around 1 km.The proposed MDR based PT-symmetric OEO reduces the bandpass filter bandwidth requirement in a single-mode OEO and implements the tunability of a PT-symmetric OEO.A dual-frequency OEO based on the nonlinear microwave amplification technique is proposed.A dual-frequency OEO with a fundamental frequency and a third-harmonic frequency was experimentally implemented.The fundamental frequency had a tuning range from 6.68 to 10.6 GHz,a tuning step of 50 MHz/m A,and an output power of 12.774±0.8 d Bm.The third-harmonic frequency had a tuning range from 20.04 to 31.9 GHz,a tuning step of 150 MHz/m A,and an output power of-5.41±1.47 d Bm.The proposed OEO provides a powerful solution for the high-performance dual-frequency microwave source.4.Research on the applications of OEOsA temperature-insensitive strain measurement system and a temperature-insensitive displacement measurement system based on a cross-reference structure is proposed.In the demonstration experiment,the strain measurement system with a measurement range of 600 ?? and a measurement error of ±0.3 ?? was implemented,the measurement results were not affected by the temperature.The measurement errors of the displacement and the velocity in the proposed displacement measurement system were ±11.14 ?m and ±3.90 ?m/ms,respectively,when the simulated target distance is around 8 km and the sample time is 1 ms,the measurement results were not affected by the temperature.The proposed OEO based sensing systems take advantages of temperature insensitivity,high measurement precision,and fast measurement speed.