Intensity and phase measurements of asymmetric mode profiles and the transform in the near- to far-field transitions

A fast and accurate measurement technique employing a calibrated CCD array is described to measure the intensity and phase distributions of the asymmetric mode profiles associated with optical waveguides. A Shack-Hartmaan wavefront sensor incorporated in the system provides the phase information. The transform describing the near-field (NF) to far-field (FF) transitions of the asymmetric mode profiles is investigated both experimentally and theoretically. The simulated NF to FF transitions using the transform are compared with the measured profiles at different positions from the end face of the waveguide. Good agreement is obtained between the measured and the computed profiles proving the accuracy of the measurement technique and also the transform used for propagation of the asymmetric mode profiles.