Patent ID: 8433205

Claim:
A method for reducing nonlinear cross-polarization modulation (XPolM) in a coherent optical communication system, comprising the steps of: double-differential rotation encoding in a transmitter, which comprises the steps of: differential encoding x-polarization and y-polarization signals P(k) independently to obtain an intermediate signal V(k); differential rotation encoding the intermediate signals V(k) concurrently with a rotation matrix Q s , wherein the rotation matrix Q s is generated by previously transmitted x-/y-polarization signals S(k); and up-converting the electrical signals S(k) to optical signals; and double-differential rotation decoding in a receiver, which comprises the steps of: down-converting the optical signal to an electrical signal R(k) with a band-limiting filter; differential rotation decoding x-polarization and y-polarization signals jointly by multiplying a unitary rotation matrix Q R , wherein the unitary rotation matrix Q R is generated a the previously received signals R k to obtain an intermediate estimate data V′(k); and differential decoding the intermediate estimate data V′(k) independently to obtain an estimate of a desired data P′(k).