>>11687800The entire premise of interferometry is to USE interfering waves to extract information that you wouldn't be able to otherwise. For instance, the phase modulation of light after passing through, say, a nonlinear crystal.
Of course, this requires that you have a good characterization of the probe light. If you are told absolutely nothing about the initial two waves, and only see fringe patterns, I don't see much you can do with that. Think about it this way: wave mechanics is linear. Two waves interfering is just a linear combination of two vectors. Such a decomposition is highly non-unique - there are many pairs of vectors which sum to the same vector.
