Research On Phase Spectrum Measurement Of Optical Waveguides Using Low Coherence Technology

Optical waveguide is a medium device that guides light waves to transmit therein,also known as medium optical waveguide.The holographic spectrum play an important role in the design and analysis of optical waveguide devices and in the reconstruction of waveguide structures.Holographic spectrum consists of amplitude spectrum and phase spectrum,the phase spectrum of the optical waveguide device indicates the amount of change in phase after the wide-band light passes through the optical waveguide device.Accurately acquiring high-resolution and high-precision phase spectrum is also of great significance in the field of fiber grating delay and measurement of dispersion and distributed sensing.At present,the research on this subject at home and abroad is still very limited.The main method for obtaining the phase spectrum of optical waveguide is the RF modulation method.However,this method has the disadvantages of expensive equipment and large error.Therefore,this paper presents a method of measuring the phase spectrum of optical waveguide device based on the technology of low-coherence interference.The principle of this phase acquisition method is studied,and the characteristics of the obtained phase spectrum are analyzed.After introducing the development process and technical advantages of low-coherence interferometry,the research status of phase measurement at home and abroad is described;the classical interference theory and Fourier transform spectroscopy are introduced,two core equations of Fourier transform spectroscopy are introduced,that is,the recovery spectrum and the interference light intensity are mutually inverse Fourier transform relationship;a method for obtaining phase spectrum of optical waveguide based on low coherence technology is proposed,that is,the optical waveguide is placed on the measurement arm,and the signal light reflected by the optical waveguide interferes with the reference light,the interference light is received by the photodetector and input to the computer to form interference data,and the inverse Fourier transform is applied to the interference data,the transformed data contains the real part and the imaginary part,the ratio of the imaginary part to the real part takes the inverse tangent function to obtain the phase of the waveguide device;the simulation of experiment obtained the phase spectrum based on the end face of the reflective fiber,the cause of phase error is analyzed.The characteristics of the phase spectrum of the obtained optical waveguide are analyzed,and the analysis and explanation are made from the aspects of phase spectrum resolution and accuracy.The results show that the resolution of the phase spectrum is related to the number of sampling points and the maximum optical path difference.The higher the sampling points or the larger the maximum optical path difference,the higher the resolution of the phase spectrum;the phase error of the phase spectrum mainly comes from the delay jitter when sampling the interference data and the quantization error of the interference data.Through employing the measuring technique of optical waveguide phase spectrum based on low-coherence interference,the phase spectrum of device with high-resolution and high-precision can be obtained.The system has a simple structure,does not require expensive experimental equipment,and has a fast measurement speed.It solves the problem that the existing methods generally have large phase errors,and has important academic value and high practical value.