A novel nondestructive technique for characterising couplers by means of a local perturbation is described. The method is studied theoretically and verified experimentally by characterising different types of fused fiber-couplers. Using this technique, both the information of the power distribution and coupling profile along the coupler waist are obtained.
C. Alegria and M. N. Zervas, "Nondestructive Coupler Characterization Technique," J. Lightwave Technol. 20, 1034- (2002)