Compact voltage-controlled all-in-fiber polarization switches are designed and investigated based on dual-core photonic crystal fibers, by selectively infiltrating one of the fiber’s cores with a nematic liquid crystal. The electro-optical control of the liquid crystal core’s optical properties allows for the splitting of the two orthogonal polarizations, showing crosstalk values lower than −20  dB in a 40 nm window at 1550 nm, for an ultracompact length less than 0.6 mm. With proper selection of the control voltage and the component length, dual-band operation with a crosstalk lower than −20  dB is also demonstrated for the 1300 and 1550 nm telecom bands.