Dual M-Z interferometer is the sensitive element of three-component acceleration seismic geophone, while Y branch waveguide is the basic optical components composed of dual M-Z interferometer, so the design of Y branch waveguide directly affects the performance of threecomponent acceleration seismic geophone. Firstly, branch waveguide and S-shaped bent waveguide are introduced, and symmetrical double Y branch S-shaped bent waveguide is designed based on this. Secondly, the bending loss of the branch waveguide is analyzed and calculated. The transmission of 1/2Y branch waveguide and 1/4Y branch waveguide , and the bending loss changes with the length of 1/2Y branch waveguide and 1/4Y branch waveguide is simulated by MATLAB. The result shows that the maximum bending loss of 1/2 Y branch waveguide is the 0.156dB, and the bending loss is close to 0 after L>320μm; the maximum bending loss of 1/4 Y branch waveguide is 0.058dB, and the bending loss is close to 0 after L>200μm. The design of double Y branch meets the requirement of low loss. Thirdly, the optical power conversion of branch waveguide in 3dB coupler is simulated and analyzed. Finally, proton exchange and Ti diffusion technique are compared; the advantages of proton exchange technology are summarized; the principle of proton exchange is introduced; and a good proton exchange annealing condition is summarized.

Objective Although comorbidities are prevalent in chronic obstructive pulmonary disease (COPD) patients, little is known about the impact of comorbidities on hospitalization costs for COPD in Chinese hospitals. This study aimed to evaluate the impact of comorbidities on hospital costs in patients with COPD.Methods We conducted a real-world, retrospective, observational study. Patients with the major discharge diagnosis of COPD at the First Affiliated Hospital of Guangzhou Medical University between December 2013 and December 2020 were enrolled. Demographic and clinical parameters were sourced from hospital data and medical records. The top 20% of patients by cost were included in the high-cost group. Univariate and multivariate analyses were used to determine the comorbidities associated with hospitalization costs. A comorbidity network was built to complement and extend the results of the multivariate analysis.Results In total, 75.7% of COPD patients had comorbidities, and the number of comorbidities had an impact on the hospitalization cost. The results of multivariate analysis showed that the comorbidities contributing to hospital costs were pulmonary embolism, sick sinus syndrome, pneumomycosis, lymphoma, lung cancer, venous thromboembolism, aneurysm, cerebrovascular disease, chronic kidney disease, heart failure, diabetes, arteriosclerosis, obstructive sleep apnea-hypopnea syndrome, and fatty liver. The results of the comorbidity network analysis were consistent with those of the multivariate analysis.Conclusion The comorbidities can influence the burden of care for patients with COPD. Therefore, attention should be paid to early risk assessment and long-term interventions for these comorbidities in COPD patients.

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