Can someone explain to me how the Vernier effect works? There are only graphs in my course, no real explanation (as it's not that important). Apparently, when you have two different signals with their own Free Spectral Range, and you somehow combine these two ranges, then there will be a wavelength shift possible for a much wider range? I don't really understand much of it. Here's the graph: http://img147.imageshack.us/img147/1114/vernierky7.jpg [Broken] I think the combining happens simply by cascading the two systems associated with these ranges. But I don't see how the effect works? All help is welcome, thanks in advance.