Do you mean this example https://optics.ansys.com/hc/en-us/articles/360042800353-Y-branch ?
How did you specify "expansion for out"? did you use port result, or have power monitor and expansion monitor? did you choose the mode to be decomposed and have the variable name to output the decomposed result?
Please check every step, and make sure the sweep can pick up the decomposed result, with proper settings. If you still cannot resolve this, please give screenshots for all related objects so we can know where is wrong.
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