Abstract: The single-layer coating and Fabry-Parot resonant cavity (FP cavity) were analyzed in principle, and the tap coating and FP cavity were modeled using the coatings tool of Zemax software. The reflectance and transmittance of single-layer coating with different refractive index materials were analyzed with respect to wavelength. The model of FP cavity was simplified and analyzed, and the reflectance and transmittance were preliminarily verified with an air-gap FP cavity with 3 mm gap. A fiber optical etalon of 50 GHz commonly used in communication was designed, and a production scheme of in-line optical etalon based on Glens collimator was introduced. Through the design, the transmittance and reflectance of the spectral ratio film of the Glens plane were controlled, and the distance between two Glens collimators was adjusted to achieve the control of the peak value, valley value transmittance and free spectral range (FSR) parameters of the FP cavity. Through the simulation, the parameters of the simulation and samples were obtained to be basically the same. The inter-sample differences, differences in spectral peak transmittance and spectral phase differences were also analyzed. Analysis of FP etalon by Zemax is convenient and intuitive, which provides a new method for FP design and analysis.