Patent ID: 7343100

Claim:
A device, comprising: a polarization beam splitter to receive an optical signal and split the received optical signal into a first beam in a first polarization and a second beam in a polarization orthogonal to the first polarization, wherein the received optical signal carries first and second signal channels via polarization multiplexing and is originally created by combining two optical beams with mutually orthogonal polarizations and unequal amplitudes which are modulated to carry the first and second signal channels, respectively; a first optical detector to convert the first beam into a first electrical signal; a second optical detector to convert the second beam into a second electrical signal; a control circuit to obtain a differential signal representative of a difference between the first and second beams and being a function of a relative angle between a polarization direction of the polarization beam splitter and a polarization in the received optical signal; and a polarization controller placed in an input optical path of the optical polarization beam splitter and to adjust a polarization of the received optical signal in response to the differential signal to set the difference to be either at a positive maximum or a negative maximum to make the first and second electrical signals represent the two signal channels.