Distributed Measurement And Analysis Of The Polarization Properties Of LiNbO₃ Optical Chips

LiNbO₃ integrated optical chips is one of the indispensable devices in some fiber optic sensors,mainly used in fiber optic current sensors and interferometric fiber optic gyroscope systems.The polarization properties of the LiNbO₃ integrated optical chips is an important indicator to evaluate its performance.The quality of its polarization properties directly affects the accuracy and precision of the optical fiber sensing system.The polarization properties of the LiNbO₃ integrated optical chips is mainly evaluated in terms of chip extinction ratio,internal crosstalk of the chip,polarization crosstalk at the coupling point between the pigtail and the chip,and the birefringence of the chip and the pigtail.The traditional intensity-based measurement method is relatively simple and can only detect and evaluate the overall polarization properties of the LiNb O₃ integrated optical chips.The measurement results include not only the extinction ratio of the chip itself,but also the extinction ratio of the test device used and the polarization of the chip pigtail crosstalk and various polarization crosstalks inside the chip,it is difficult to accurately measure the polarization properties of the chips and whether there are defects inside,and it is easily affected by external factors,such as the stability of the light source,the coaxiality and collimation of the optical path.At the same time,due to the accuracy limitations of some devices themselves,there are certain limitations to the measuring of high extinction ratio chips.Therefore,there is an urgent need to accurately evaluate and measure the polarization properties of integrated optical chips.This article uses ghost-peak free distributed polarization crosstalk analyzer to study and analyze the limitations of the existing LiNbO₃ integrated optical chips polarization properties measurement.The main research contents are as follows:Starting with the principle of white light interference,the concepts of the signal composition and coherence length are introduced.The signal analysis of white light interference is theoretically deduced,and with the help of the relevant knowledge of white light interference theory,the ghost-peak free distributed polarization.The test principle of the crosstalk analyzer is described in detail,focusing on the principle of ghost peak elimination and the effect of the presence or absence of ghost peak elimination devices on the interference signal;Secondly,it explains why it is necessary to measurement the polarization properties of LiNbO₃ optical chips,and the importance of its advantages and disadvantages in application;it analyzes the influence of polarization crosstalk error on its accuracy in fiber optic current sensors and fiber optic gyros,mainly from fiber the principles of current sensors and fiber optic gyros,the causes of polarization crosstalk errors,and the role of integrated optical chips in these three aspects are explained;Then,the measurement optical path of the LiNbO₃ optical chip is constructed,and the defect points inside the chip are included in the theoretical analysis.Combined with the principle of the measuring instrument,a detailed theoretical derivation is made.First,the Jones matrix is used for theoretical derivation,and secondly,the image method is used to represent it more visually,and the two theoretical analysis methods are cross-validated;Then,the distributed measurement and experimental results of Li NbO₃integrated optical chip were analyzed.According to the constructed theoretical model,the integrated optical chips is measured,and the results are analyzed.The results are consistent with the theoretical derivation conclusions,and the hypothesis of the internal defects of the test chip is verified.In order to simplify the steps of reading data,a program for automatically finding data is written in matlab,and can correspond to manual reading;Finally,using a single-polarization fiber similar to the polarization properties of the LiNbO₃ integrated optical chips?Y-waveguide?,the known defect points were simulated and measured to further verify the rationality of the measured Y-waveguide results;The experimental results prove that using the ghost-peak free distributed polarization crosstalk analyzer system,the polarization properties of the two types of LiNbO₃ optical chips of straight and Y waveguides can be distributed.According to the measurement results,the extinction ratio of the entire chip can be obtained by integral calculation,the crosstalk value of the connection point of the pigtail and the waveguide can be directly read,and whether there are defect points inside and the position and size of the defect point can be detected.This article provides a more reliable method for screening and verifying the quality of LiNbO₃ integrated optical chips,and it is of great significance to improve the manufacturing process of LiNb O₃integrated optical chips.