Research On Thermo-optic Mode Switch Based On Polymer Mach-Zehnder Interferometer

Due to the non-linear effect of the fiber and the restrict bandwidth of the fiber amplifier,the communication capacity of the single-mode fiber is close to the limit.In order to meet the future demand for high-speed communications,mode division multiplexing technology came into being.In the mode division multiplexing system,the transmitter needs to convert the fundamental mode into high-order mode and then couple them into the few mode fiber.Therefore,the mode switch which can realize flexible mode switching becomes the key device in the mode division multiplexing system.In order to suit with other devices in the mode division multiplexing system,the mode switch should have a compact structure and easy integration features,so the mode switch based on planar optical waveguide technology is a good choice.At present,the optical waveguide material is divided into two kinds: organic materials and inorganic materials.Organic materials mainly include various kinds of polymers,inorganic materials including silicon and silicon compounds,lithium niobate,etc.Because of its simple and convenient production process,low cost of materials,high thermal coefficient and easy to fabricating three-dimensional devices,polymer optical waveguide devices are attracting more and more researchers' attention.The dissertation is about the mode switch based on thermo-optic effect,including the plane structure of the MZI and three-dimensional structure of the MZI mode switch.The dissertation mainly includes the following four parts:Firstly,the background of the mode division multiplexing system and the research status of the mode switch device are introduced.Optical polymer material and corresponding waveguide fabrication are briefly analyzed.Secondly,the structural parameters of the device are analyzed by using the Marcatili method,MATLAB and Comsol respectively.Then,the thermo-optic simulation is carried out by Comsol thermal diffusion model.Based on the calculation and simulation results,the preliminary device design parameters are obtained.And then simulates the optical path of the device in Rsoft,the simulation results can be expected to achieve the desired results.Thirdly,the plane structure MZI thermo-optic mode switch is fabricated and tested,and improves the fabrication process of the device.The test results show that the mode switch has a weak polarization correlation and works over the entire C + L band.The mode switching requires only about 9mW,and the extinction ratio of the device is up to 23 dB.The insertion loss of the whole device is about 14 dB.The test result agrees with the expected targets and verifies the correctness of the simulation.Finally,the three-dimensional structure MZI mode switch is designed and fabricated,for the complexity of three-dimensional structure,the design of the marks of mask and the corresponding fabrication process are improved in this dissertation.