Broadband reset-free automatic polarisation controller

A novel electro-optic polarisation controller is proposed and demonstrated that allows reset-free endless polarisation transformations between any two varying general polarisation states. The 1.5 μm controller is realised with standard lithium niobate waveguides, has an optical bandwidth in the order of tens of nanometres, and is electrically tunable over a wide wavelength range. Automatic polarisation control with an entirely analogue electronic feedback loop is demonstrated.