Design On Polarizing Beam Splitter (pbs) Of Roadm

Reconfigurable optical add/drop multiplexer (ROADM) is a significant node equipment which can achieve the process that nowadays WDM system evolves into All Optical Network. It can download certain wavelength from the multi-wavelength input signal to local, but also has the foremost capability of dynamically reconfiguration. Thereby, it accelerates the process of intelligentizing the optical network.Polarization beam splitter and the polarization conversion unit constitutes the entire ROADM devices, integrated polarization beam splitter (PBS) is the role of split or merger TE mode and TM mode. So this paper aims to design a PBS with high extinction ratio and high transmittance.Most of the existing PBS technology based on fiber or waveguide type devices, which induce low finished products ratio, low extinction ratio, hard to control, and unsuitable for integration. In order to meet the new generation optical network requirements, this paper proposes a PBS based on Ti:diffuse lithium niobate waveguide. The device produced in Ti:LiNbO3, utilizing the mode coupling to split TE and TM mode which propagate through the output port respectively.This thesis starts with the fundamental principles of crystal birefringence, mode-coupled and some other theories and then discuss two common fabrication method especially deduces how the device's parameters affect its performances. Moreover, the paper uses mode coupling theory to derive the theoretical model of two kinds of PBS structure and the mode splitting conditions, finally calculate the geometric parameters of the device and the fabrication parameters. In the end, the paper proposes an optimization of using electrodes to improve the performance.The simulation results show that the design of PBS in this paper performs high integration, high extinction ratio and low transmission loss. Furthermore, it can modulate the extinction ratio and index difference without changing the device structure.