Acousto-optic Tunable Filter Coupling Theory And Its Design

As a key optic wave-guided unit, acousto-optical tunable filter (AOTF) has wide foreground in optical communication. An acousto-optical tunable filter which can be used to conceive optical network nodes, such as OADM and OXC, has been designed. Polarization-independent AOTF has not only increased its flexibility, but also widen its usage in the network, and mode-splitter is the key component to achieve AOTF's polarization-independent characteristic. The thesis describes the design method of AOTF's waveguide, mode converter and mode-splitter, and gives the design results.Basing on the theory study, AOTF's design has been given out, mainly including three aspects:1. Optical waveguide has been designed. According to the principle that the waveguide being designed must be single-mode, the curve between the width of Ti strip and its thickness has been given out. Then, the mode field of this waveguide has been analyzed using Beam Transmission Method (BPM). According to the simulation, we have found that the waveguide is single mode and can match with the single-mode fiber.2. Basing on acousto-optic coupling theory, mode converter has been designed.3. Mode-splitter has been designed. Using BPM method, it has given out the mode-splitter's design results, especially getting the curve between coupling length and forficate angle. Theses curves denote TE mode has 100% conversion efficiency or TM mode's conversion efficiency is zero. Then, the point which satisfies TE mode having 100% conversion efficiency and TM mode having zero conversion efficiency at the same time can be obtained. Finally, we analyzed performance of mode-splitter using BPM.