Nondestructive characterization of fiber couplers by a local perturbation method

A technique for the nondestructive characterization of fiber couplers is demonstrated. A CO/sub 2/ laser beam is scanned along the coupler length inducing a local perturbation to the coupler eigenmodes. Information about the power evolution and the coupling-constant variation along the coupler length can be obtained by applying an asymmetric and symmetric perturbation, respectively. Experimental results of the characterization of a half- and a full-cycle fiber coupler using this technique are presented.