Spectral Characteristics of Uniform Fiber Bragg Grating With Different Grating Length and Refractive Index Variation

ABSTRACT: The spectral response of the uniform FBG with different grating parameters such as grating length and index change are provided and discussed. The coupled mode theory is a suitable tool for analysis and obtaining quantitative information about the spectrum of a fiber Bragg grating. The coupled mode equations can be obtained and simplified by using the weak waveguide approximation. The spectrum characteristics can be obtained by solving these coupled mode equations. In this paper simulation of FBG has been carried out to analyze the spectral characteristics of the FBG. An optical FBG is being simulated with the help of advanced software module such as the R soft and the modeled sensor is evaluated for the grating and different efficiency of various grating shape parameters, modulation depth,etc. The relationship between the maximum reflectance, 3dB bandwidth and centre wavelength with grating parameters are also given and discussed. Optimization and improvement of the system can be realized by using the simulation results. Since the present work not only deals with theoretical aspects of FBGs but also leads to the development of simulation tools which can be used in the area of communications and sensors

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population