Pulse circulation measurement of transmission characteristics in long optical fibers

A pulse circulation method to measure the length dependence of transmission characteristics in optical fibers is described. In principle, the method has the advantage that no unnecessary power is branched off in the loop. Using this method, the length dependence of transmission characteristics of step and graded index fibers has been measured and found to be different in both cases. It is concluded that the difference is due to the material dispersion effect, which significantly influences pulse spreading in long length graded index fibers.