Determination of the "field radius" /spl omega//sub /spl infin// from bending loss measurements of optical fibers with arbitrary index profile

A new method to determine the field radius /spl omega//sub /spl infin// from the bending loss of the guided fundamental mode is presented. Experimental results verify the validity of the method. The accuracy of the method is basically determined by the accuracy of the bending loss measurement. It is shown, that the whispering gallery modes will not reduce the accuracy of the method significantly. The method is applicable to any single-mode fiber with arbitrary refractive index profile, whereas the method used by now (far field) is only applicable to matched clad structures. Furthermore, it is shown, that an effective bending radius must be used in order to compare the results of the far field and bending loss measurements. For the first time a method to measure the effective bending radius is given.