Mode conversion coefficients in graded-index fibers with various fiber-coating schemes: measurements

Mode conversion coefficients in graded-index fibers with various fiber-coating schemes are measured. The experiment proved that graded-index and step-index fibers agree in the order of magnitude of parameters representing random bends along the fiber axis. It is found that mode conversion coefficients are largely concerned with the structure of the coating. The results show that mode conversion characteristics are affected by structure of the coating and refractive-index depression at the center of the fiber core. The combination of a relatively hard jacket and a thick isolation layer made of soft material is found to be effective in reducing the mode coupling among samples investigated.