Design And Research Of Optical Add-drop Multiplexer Based On Fiber Gratings

Recently, Optical Add-Drop Multiplexer(OADM) has received extensive attention of the communications industry with its advantages of low insertion loss, low cost, and the polarization independent characteristics. Focused on the phase-shifted fiber Bragg grating(PSFBG) and OADM as the key researches, a structure of OADM based on PSFBG and Mach-zehnder interferometer(MZI) is studied, which can implement two wavelength channels’ uploading and downloading.Furthermore, this paper proposes a novel model of the two-way transmission tunable OADM based on FBG and PSFBG. The main completed works are as follows:1. Based on recent domestic and foreign studies, we introduce the development and applications of wavelength division multiplexing(WDM) technology and fiber grating in optical fiber communication system as well as several common OADM structures and their operating principle.Theory researches, such as Coupling Mode Theory and Transfer Matrix Method, are used for PSFBG reflectivity formula, which result in the achievement of the reflective and transmission spectra of FBG and PSFBG.2. By changing the grating length, refractive index modulation depth and phase shift angle, this paper analyses the reflection spectrum changes of single-point PSFBG and multi-point PSFBG respectively. Multi-point PSFBG has the similar conclusions with single-point PSFBG, when grating parameters change. In order to suppress the side lobe interference of reflection spectrum,apodization functions, such as Gauss apodization, etc. are used to optimize the reflection spectrum.With the changes of grating parameters, the physical model has been designed to study the single-point and multi-point PSFBG spectra, as well as the apodization by Rsoft software.Furthermore, a special phenomenon of center wavelength shift on PSFBG has been found.3. A novel model of two-way transmission tunable OADM based on FBG has been proposed in this paper, which has the advantages of high flexibility, high device utilization rate and low crosstalk. In addition, two channels do not interfere with each other and can upload/download in a specific wavelength effectively. Two-way transmission could improve the fault tolerance and the reliability of the WDM system. According to the simulation results, the side mode suppression ratio of downloading wavelength is around 20 dB, which can realize multiplexing and demultiplexing functions preliminarily. Research and analyze a structure of OADM based on PSFBG and MZI,which can implement two wavelength channels’ uploading and downloading. Furthermore, thispaper proposes a OADM model based on phase-shifted fiber grating, and provides the preliminary feasibility analysis.