Hi, yes, the coupler elements in INTERCONNECT are "point couplers", so they don't include the change in phase from propagation through the coupling region. This change in phase can be included in the straight waveguide components by including the length of the coupling region in the waveguide sections, as you mentioned.
Alternatively, you can calculate the S-parameters of the coupling region in a physical solver like FDTD and import this data into an S-parameter element in INTERCONNECT. In this case, the S-parameters include the phase shift data, so the length of waveguide included in the S-parameter data (in other words, the waveguide between the ports in FDTD) should not be included in the waveguide elements.
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