Thermo-optic Mode Switches Based on Three-dimensional Polymer-waveguide multi-arm Mach-Zehnder Interferometers

Project: Research

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The global demand for communication bandwidths is growing rapidly, which owes muchto the continuous increase in the Internet traffic. There is an urgent need to largelyincrease the transmission capacities of optical networks to satisfy the market. Mode-divisionmultiplexing (MDM), which allows different modes in a multimode fiber to carrydifferent channels, is a particularly promising technology for enhancing the transmissioncapacity of a fiber, and is a focus of research in the field of optical communicationsworldwide. The goal of the project is to demonstrate a new and powerful opticalwaveguide platform for the implementation of mode-switching devices forreconfigurable MDM applications.The key waveguide structure to be considered is a three-dimensional (3D) thermallytunable Mach-Zehnder interferometer (MZI) formed with four single-mode waveguidearms. The four waveguide arms are arranged in two layers and merged with waveguidebranches into few-mode waveguides at both ends, where four spatial modes aresupported. To achieve switching among the four modes, each waveguide arm of the MZIincorporates a heating electrode for tuning the phase of the light wave. By controllingthe phases of the light waves in the four arms, any mode launched into the MZI can beconverted into any other mode at the output of the MZI. While the 3D four-arm MZIitself is a very useful mode switch, it can be integrated with a matching 3D fixed four-mode(de)multiplexer to spatially separate the modes. This integrated device thus allowsany input mode to be switched to any of the four output ports, a function that isimportant for a reconfigurable MDM system, where different mode channels are routedto different branches of the network, depending on the network traffic. In this project,these 3D devices will be designed and fabricated with polymer material.The polymer waveguide technology used in the project allows the formation of multilayerstructures, which is essential for the realization of the proposed 3D devices. The largethermo-optic coefficient of polymer material also promises efficient thermal tuning,which is important for achieving the proposed switching functions. The projectcapitalizes on the long history of successes at CityU in the development of novel opticalwaveguide devices based on the polymer waveguide technology, including the recentworks on fixed mode (de)multiplexers. The waveguide platform developed in the projectserves to pave the path for the future development of reconfigurable optical networksbased on the high-density MDM technology.


Project number9042341
Grant typeGRF
Effective start/end date1/01/1724/12/20

    Research areas

  • optical switches , optical waveguides , polymer waveguides , mode-division multiplexing , thermo-optic effect