Visibility of interference fringes: Effect of the optical guide length in coherent light

The visibility of the interference fringes produced by a wavefront of coherent light passing through an optical guide, divided, and recombined is studied. A cladding fiber and a light-focusing fiber are used as the optical guide. The relationship of the visibility of the interference fringes to the length of these fibers is determined. The visibility of the interference fringes produced through the light-focusing fiber and those produced through the cladding fiber are almost independent of the length of the fiber despite random internal reflection.