Electrically controlled optical switch for multimode fiber applications

An electrically controlled optical switch based on polarization principles is described. It uses a liquid crystal twist cell that rotates polarization by 90 degrees , and it operates on an ac voltage that switches between 0.8 and 2.5 V rms. The switch has a loss of ~0.4 dB, neglecting reflections, in an unpolarized incoherent beam and a cross-talk ratio of ~-20 dB. It operates in collimated light, but it can be applied to multimode fibers using collimating lenses, which are expected to add <0.8 dB to the loss.