Ansys Insight: Optical ports: Extracting s-parameters

    • Shin-Sung Kim
      Ansys Employee

      The concept of a port was introduced into FDTD in the 2017a release. New objects called ports can be added to a simulation and used to extract the equivalent circuit representation of a device. A port is usually defined as a cross-section on a waveguide structure or a connector, and it serves as a reference point to extract an equivalent circuit representation. The port objects in FDTD can be used to excite all the ports of a device in order to extract a complete S-parameter representation. At the bottom of this post, you will find a simulation file and a script with a simple example. The simulation file consists of a straight glass waveguide with two ports. To extract the full S-parameter matrix, all the ports must be excited individually using separate simulations. In this example, two simulations are needed: one to excite port 1 and extract S11 and S21, and another one to excite port 2 and extract S12 and S22. This process can be carried out by hand or in an automated way using the new S-parameter sweep tool. The two approaches are briefly illustrated here.

      Extracting S-parameters by Hand

      The attached script extracts S11 and S21 and compares them against the expected results. First, the script sets the first mode of port 1 as the exciting port. This is done with the following two commands:

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