A special kind of microstructured optical fiber is proposed and fabricated in which, in addition to the holey region (solid core and silica-air cladding), two large holes exist for electrode insertion. Either Bi-Sn or Au- Sn alloys were selectively inserted into the large holes forming two parallel, continuous and homogeneous internal electrodes. We demonstrate the production of a monolithic device and its use to externally control some of the guidance properties (e.g. polarization) of the fiber.