Novel SOI Passive Optical Waveguide Devices Based On Two-dimensional Diffraction Theory And Spatial Filter Theory

Integration has been a major tendency of the modern optical waveguide devices.The SOI platform is regarded as a most promising integrated optics solution for many advantages such as high index contrast,small size and compatible with the COMS fabrication technology.Various passive optical waveguide devices have been successfully realized on SOI platform,especially for optical wavelength demultiplexer and power splitter.This dissertation presents a novel planar waveguide super-multiple-channel optical power splitter and a hybrid optical wavelength demultiplexer/power combiner for TWDM PON.The designs both use the wavefront lateral interference theory of diffraction optics and spatial filter theory.The design of super-multiple-channel optical power splitter uses the wavefront lateral interference and spatial filter theory.Upon splitting spatial DC and AC frequency components of a phase grating,DC component is inverted due to a phase delay unit,and then all components are merged again,the output field is added constructively in one part and cancelled in the rest in each segment.Such addition and cancellation repeat from segment to segment thereby to split the incident beam into N channels.The design scheme is innovative and different from traditional optical power splitter,with the advantage of super multiple and extendible output channel number.Following the principle explained above,we have designed and simulated the optical power splitter with 256 output channels on an SOI platform.The required size is within 1.2mm by 5mm.Our numerical simulation results show that,for working wavelength 1550nm,the insertion loss is 1.1dB and the channel non-uniformity is 1.7dB.We have proposed a single passive optical device that can function as a 1×N wavelength demultiplexer for downstream signal transmission and simultaneously as a N×1 optical power combiner for upstream signal transmission.The whole device structure is based on a traditional AWG functioning as a wavelength demultiplexer for the downstream signal.However,modifications are introduced to incorporate the combiner design for the upstream signal aiming at not jeopardizing the wavelength demultiplexing performance.We have designed and simulated the hybrid optical wavelength demultiplexer and power combiner(taking the 32 channel device as an example)on the silicon-on-insulator(SOI)platform.The device size is about 900×2500 ?m2.Our numerical simulation result shows that the insertion loss and adjacent channel crosstalk of the downstream wavelength demultiplexer are as low as 4.6dB and-16.3dB,respectively,meanwhile the insertion loss and channel non-uniformity of the upstream power combiner can reach 3.5dB and 2.1 dB,respectively.