what is fringe shift?

callejon

I'm working on a modification of Fizeau's experiment in 1851 about the addition of velocities. I've derived the formula for the fringe shift. But the problem is I actually don't know what it is. I know it's the movement of the interference pattern. But it has no unite, so what is the meaning of a fringe shift of let's say 0,3. Or how can I determine the fringe shift in the interference pattern?

clive

Maybe you calculated the "phase shift" and then is obvious you got something adimensional (that is rad) ......