A twin-hole fiber was provided with Au-Sn alloy electrodes and thermally poled at 255 masculineC with 4.3 kV applied during 155 minutes. An electric field 6X107 V/m was recorded. The poled fiber was cleaved and etched, revealing that the depletion region overlapped the entire core, was wedge shaped and pointed towards the cathode. The recorded profile closely followed the spatial distribution of the poling field.