interference between two waveguides.

I want to see the interference between two waveguides.
It is simple. There are two waveguides. And laser inputs are on the end of the waveguides.
So I need two inputs.

By using a boundary mode analysis I found the field on the first input face.
But I don't know how to set two inputs..

For my method I set two inputs as port 1 and 2 in the boundary setting tab. And I set the wave excitation at each port.
I think the results will be symmetry, right?

But the field is not symmetry as you can see.
Please help me

Thank you!