| Optical waveguide(OW)is widely used in optoelectronic integration,light source,sensing,communication and other fields.The holographic response spectrum of OW includes amplitude and phase spectrum,which characterizes the optical and structural characteristics of OW,and plays an important role in the analysis,design and application of OW.Phase is extremely sensitive to structural changes and noise interference,and phase spectrum acquisition is relatively difficult,which constrains the research and application of holographic spectrum.The acquisition methods of phase spectrum have also been studied at home and abroad,including radio frequency modulation,interferometry,pulse scanning,Hilbert transform,etc.However,there are some problems such as single measurement,high cost,complex operation and low precision,which are not mature.For this reason,our group proposed a method to obtain both the amplitude spectrum and phase spectrum of optical waveguide devices,i.e.the low coherence holographic spectrum based on Fourier transform.The main work of this thesis is based on this method to establish an experimental system for holographic response spectrum of OW devices and analyze its characteristics.Firstly,the principle of obtaining the optical waveguide holographic spectrum by low-coherence interferometry is analyzed and the processing method of interference signal is introduced,including discrete Fourier transform and phase unwinding method.Then,on the basis of analyzing the characteristics and requirements of the system,an experimental system consisting of hardware and software is established,including a precision low coherence system based on Michelson interferometer,an equal-time data acquisition system,a motion control and data acquisition and processing software system based on LabVIEW.Finally,in order to verify the feasibility of the proposed method,the holographic spectra of fiber end face and Fabry-Perot(F-P)cavity are simulated by using low coherence principle and multibeam interference principle respectively.The holographic spectra of fiber end face and Fabry-Perot cavity are measured by using the established low coherence holographic spectrum acquisition system,and analyzed and compared.The comparison results show that the theoretical simulation results are basically consistent with the measured results,which proves the feasibility of the method.Furthermore,the holographic spectrum of optical waveguide devices is obtained by double Michelson interferometry and Fourier transform,which eliminates the measurement error caused by the non-uniformity of light source.The feasibility of the low-coherence holographic spectrum acquisition system based on Fourier transform is analyzed and verified theoretically and experimentally,and the experimental basis for further analysis and application of OW holographic spectrum is established. |
