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A unified method was proposed to reduce the beat length of a multimode interference (MMI) coupler. By properly adjusting the phase difference of the N-fold images, the mode evolution is changed to generate self-images at a much shorter distance. The effect of adjusting the phase difference can be regarded as dividing the original MMI coupler into multiple sub-MMI couplers. Such an effect can be applied for both symmetric- and paired-interference cases. We applied the principle to design compact optical splitters operating at dual wavelength bands. The simulation shows that excellent performance with reduced coupler length can be obtained for splitters operating at both 1.3 and 1.55 mum bands.

A coarse wavelength division multiplexer is designed on a silicon-on-insulator waveguide using the Mach-Zehnder interferometers with novel multimode interface-periodically segmented waveguide couplers and segmented waveguide arms. It is viable for metro and access applications, since it can be inexpensive and provide easy fabrication, compact size, and good output performance. As a design example, the channel spacing of the demultiplexer is chosen to be 24.5 nm for applications to the 10-Gigabit Ethernet. The simulation results show that the wide-passband demultiplexer can have insertion loss less than 2.3 dB and crosstalk better than 18 dB.

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CAD tools are becoming increasingly powerful today. They provide users with more efficiency and improve the overall performance of design activities. CAD software publishers include specific tools that are dedicated to knowledge management in order to achieve this design performance and significant savings. The use of these tools and certain functions is nevertheless context-oriented. A decisional model for the use of knowledgeware has therefore been developed here, and the application of knowledgeware in different industrial cases is discussed.