Study Of A Tunable Optical Add-drop Multiplexer With Low Crosstalk

Optical add-drop multiplexer(OADM)is a key element of wavelength division multiplexing(WDM)optical network.Nowadays,the optical network communication which has high speed,large capacity,transparency and other characteristics is undergoing rapid development,during which an optical add-drop multiplexer plays an extremely important role.Optical add-drop multiplexer is one of the key techniques of modern communication network and significant efforts have been invested in almost all the countries in the world.In this thesis,we investigate the main development trend of OADM,that is,how to reduce the crosstalk,improve the bandwidth,improve the integration and etc.A new taper structure based on the traditional cross micro-ring is introduced.It can effectively reduce the crosstalk,while reducing the structure size of the device,and thus provide excellent basis for the subsequent multi-channel cascaded micro-ring OADM devices.First,we introduce the cone-shaped cross structure and the self-mapping mechanism of the taper structure,and then the Finite Element Method(FEM)and Finite-difference Time-domain algorithm(FDTD)are utilized to simulate the performance of a linear cone-shaped crossed waveguide.The COMSOL simulation results show that the insertion loss of the linear conical crossed waveguide is greatly reduced,and the transmittance at wavelength 1550 nm can reach more than 95%,which is of great value to the actual fabrication of the device.Combing the microstructures with linear cone-shaped cross structures and simulated by Lumerical FDTD and Matlab simulation software,the transmittance of the through end is as high as 93%,which is 13% higher than 80% of that of the traditional cross structure,and this provides a good numerical simulation basis for the multi-channel device cascade and the actual production.On the basis of numerical simulation,we fabricate and test the device in the optical waveguide lab of Zhejiang University.The electron beam lithography equipment is utilized in the clean room.At the same time,we use an inductively coupled plasma etching equipment and a plasma enhanced chemical vapor deposition apparatus,respectively,in the etching and film growth of nanometer waveguide.After a series of processes such as the SOI wafer cleaning,the silica growing,the CH4 processing,evenly gluing,pre-baking,exposuring,developing,post-baking,etching,removal of photoresist and the silicon dioxide cladding growing,the production of the device is completed.At last,a test platform is built where light with a certain wavelength from a tunable laser is coupled into the chip to be tested by the grating coupling technology,and received and displayed by an optical power sensor.After comparing the experimental results with the corresponding numerical simulation,we evaluate the performance and problem of the device.