Integrated-Optic Devices Based on the Multimode Interference Effects

• Main Authors: Yen-Juei Lin, 林晏瑞
• Other Authors: San-Liang Lee
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/56967873665368266825

博士 === 國立臺灣科技大學 === 電子工程系 === 92 === The subject of this thesis is on the design and analysis of multimode interference (MMI) based optical passive devices for wavelength-division-multiplexing (WDM) networks. We propose a novel 1.3/1.55-um wavelength demultiplexer on the InP material system. A chirp grating is placed inside an MMI structure to shorten the device length and increase wavelength tolerance. Simulation results show that a demultiplexer with insertion losses of 0.8 dB and 0.03dB and isolation ratios of 26 dB and 41dB can be obtained at 1.55- and 1.3-um wavelengths, respectively. An approach that can reduce the N-fold self-images interval of the MMI waveguide is presented. By placing partial index-modulation regions in a multimode waveguide, a paired-interference mechanism and a symmetric-interference mechanism will exist simultaneously. We provide a simple design principle to shorten the device length. As an example, a novel 1N dual-band optical power splitter on the silica waveguide is designed. The coupling characteristics have good tolerance on the device length and wavelength variation. We also propose a novel 1.3/1.55-um dual-band optical 2X2 switch with sixteen switching states. It consists of a Mach-Zehnder interferometer (MZI) with two dual-band 3-dB MMI couplers. The switch can have insertion loss less than 0.43dB and crosstalk larger than 27.4dB. A 1X4 coarse wavelength division multiplexing (CWDM) demultiplexer is designed on the silicon-on-insulator (SOI) waveguide using the MZI configuration with periodically segmented waveguide (PSW) arms and novel MMI/PSW couplers. The channel spacing of the demultiplexer is chosen to be 24.5nm for applications to 10Gbps ethernet. The simulation results show that the wide-passband demultiplexer can have insertion loss less than 2.3dB and crosstalk larger than 18dB. A 1dB bandwidth of 18nm was obtained to provide good tolerance on wavelength variation.