Research And Application Of Chirped Microwave Signal Based On Optically Injection Semiconductor Laser

The chirped microwave signals usually have high frequency sweeping speed,which can reflect the instantaneous frequency of the microwave signal in the change in time.By using the high-speed frequency sweeping characteristic of the chirped microwave signal,the frequency domain measurement which is limited by the response speed of the measuring equipment is transformed into the high-speed measurement in the time domain.It provides an effective solution to improve the measurement speed and reduce the cost of the system.In this thesis,the generation characteristics of chirped signal under period-one oscillation are studied.On this basis,a high-speed measurement technology based on optically injection semiconductor laser is proposed and applied to the field of sensor and Li DAR.The purpose of this technology is to use high-speed chirped signal to achieve high-speed measurement in time domain and provide high-speed demodulation scheme for sensor and Li DAR.The main work of this thesis is as follows:(1)A novel high-speed and high-resolution optical fiber sensor based on optically injection semiconductor laser and microwave filtering is proposed.We use a FBG as the strain sensing element,and add the FBG into a ring cavity laser to achieve narrow linewidth output to improve the measurement accuracy.After coupling the chirped optical sideband generated by an optically injection semiconductor laser with the output of the ring cavity laser,the chirped microwave signal with symmetrical positive and negative chirps is generated after frequency beating.After two electrical pulses are obtained after a narrow-band microwave bandpass filter,the instantaneous wavelength variation of the FBG is transformed into the pulse time interval change in the time domain.The sensor achieves a measurement speed of 1MHz and a measurement sensitivity of 17.3 ns/με.By measuring the absolute time interval between two pulse envelopes,the measurement ambiguity is eliminated and the sampling rate of oscilloscope is greatly reduced.(2)A novel high speed and high sensitivity RF sensor based on optically injection semiconductor laser and time measurement technology is proposed,and the proof-ofconcept experiment is carried out.After the chirped microwave signal is generated,a narrow-band adjustable microwave bandpass filter is used to replace the temperaturesensitive bandpass filter to filter the chirped microwave signal,and the frequency-time mapping is completed.A measurement speed of 1 MHz was achieved in the experiment.By changing the amplitude and frequency of the triangle signal and the power of the injected light,the measurement speed and sensitivity of the sensor can be easily and flexibly controlled under different scene requirements.(3)A novel frequency-modulated continuous-wave Li DAR technology based on reservoir computing(RC)is proposed.After the time domain waveforms of IF signal in the range of 2m-2.1m are trained and classified by RC,the measurement accuracy of1 cm is achieved,and the measurement speed of the system is effectively improved without increasing the complexity of the system structure.