If you emit two coherent waves with a phase difference of 180 degrees, they will immediately cancel each other before hitting any object. There is no way to "filter" one out. The same holds for two voltage waves on a line: you cannot filter out one or another if they have the same frequency and are coherent.
You can use two synchronous signal (or ray) sources but once you allow them to combine, there is no way to separate them. You can only control them AT THE SOURCE, not later.