New method for measuring dispersion-zero variation along a fiber without destroying the fiber

We present a nondestructive technique for measuring dispersion along the length of a fiber. It is based on the fact that four-wave mixing between two optical waves in a fiber will be enhanced when one of the two waves lies on the dispersion zero of the fiber. By using pulses with different group velocities in the fiber, the four-wave mixing can be made to occur at some localized region of the fiber and hence a map of the dispersion zero can be obtained.