Patent ID: 6950611

Claim:
An active polarization control arrangement for use in an optical transmission system, the active polarization control arrangement comprising a polarization control element responsive to an input optical signal propagating along an optical fiber transmission path and further comprising a correction signal input, the polarization control element for producing as an output an optical signal exhibiting a predetermined state of polarization; a complete in-line fiber polarimeter formed as an integral part of the optical fiber transmission path at the output of the polarization control element and configured to out-couple signals determined by the state of polarization of the input optical signal, the complete in-line comprising a set of four filter elements incorporated in the optical fiber transmission path, each filter element tilted at one of the predetermined angles of 0°, 60°, 150°, and 90°, with a waveplate oriented at an angle of 30° with respect to the optical axis disposed between the second and third filter elements; and a feedback control element responsive to the out-coupled signals from the complete in-line fiber polarimeter, said feedback control element far providing correction signal inputs to the polarization control element based on the out-coupled signals from the complete in-line polarimeter.