All-fiber Fourier Transform Spectrometer Modeling And Design With PZT Phase Modulation Real-time Compensation

Fourier transform spectrometer has the advantages of multi-channel,high luminous flux and high spectral resolution,especially in the field of infrared spectroscopy test and measurement.With the booming development of the spectrometer market,the requirements for miniaturization and portableness of instruments are increasing,and the development all-fiber Fourier transform spectrometers is particularly important.Piezoelectric ceramic transducers(PZT)are commonly used in all-fiber Fourier transform spectrometers(FFTS)to achieve phase modulation.The performance of PZT for fiber phase modulation directly affects the accuracy and reliability of optical instruments.In this thesis,the core technology of PZT phase-modulated FFTS was studied,and theoretical derivation and compensation experiments were carried out on the possible spectral errors.A new system design was proposed,and a real-time compensated all-fiber Fourier transform spectrometer was built.The main contents of the thesis are as follows:1)According to the basic theory of Fourier transform spectroscopy,the basic principles of interference model,spectral resolution and apodization function are demonstrated.Combined with the theory of fiber optics and phase modulation,the hysteresis-nonlinearity performance of PZT and its influence on optical phase are analyzed.Secondly,the sampling error of two sampling method with equal-time interval and equal-optical path difference interval is derived,including the spectral error caused by the PZT stroke turning point.Finally,the spectral errors caused by the fiber dispersion are deduced and analyzed.2)Combining PZT performance and fiber dispersion characteristics,a theoretical model of FFTS was established.The main factors affecting the spectral error and the instrument resolution are systematically derived,and t a new FFTS system is designed to provide a real-time compensation method for spectral error: First,the parallel winding of optical fibers method: In order to solve the common mode noise caused by PZT hysteresis-nonlinearity and the coupling difficulties of light of different bands,a dual Mach-Zenhder interferometer is used and wind the sensing arms of the two interferometers in the same PZT cylinder.It can achieve that the dual optical path experiences consistent and synchronized phase modulation.The second is the single-stroke scanning sampling method: The FPGA timing control DAC and ADC circuit are used to achieve selective sampling of the test interferogram on the single pass of the PZT,avoiding the spectral artifacts generated by the phase discontinuities of the PZT.Third,by simultaneously acquiring the interferogram generated by the reference interferometer,a narrow linewidth laser spectrum is obtained for real-time calibration compensation of spectral shifts due to dispersion for wide band light.3)The prototype of the FFTS was developed,and the hardware circuit and software design of the spectrometer system were demonstrated in detail.The hardware design includes the photoelectric receiving circuit;the signal processing and filtering circuit;the PZT high-voltage driving circuit;and the data acquisition system based on FPGA+USB.The software platform is built on the VC-based upper computer,which realizes data acquisition,storage and waveform display.4)Through the comparison of the original interferogram and the spectrum with the compensated,the experimental results verified that the system design can effectively compensate the spectral error caused by PZT and the fiber dispersion.Finally,the potential problems that in the actual spectral measurement of the FFTS prototype are discussed and improved.