A Polarisation Control Scheme For Coherent Optical Systems

This paper describes the design and construction of a polarisation control device which uses four liquid crystal cells. This device has a low fibre to fibre insertion loss and a low drive voltage. A novel polarisation control algorithm has been developed which produces the required state of polarisation and simultaneously optimises the voltage applied to each element. The algorithm avoids the need for careful calibration of the elements. Tests have been carried out which demonstrate that the controller and algorithm can successfully track polarisation changes.