Patent ID: 6661549
Filing Date: 2003-12-09
Classification: H04J

Abstract:
A method of optically demultiplexing a stream of optical information signals belonging to a plurality of time division multiplexed tributary channels, comprising the steps of:extraction signals relating to a given channel by exploiting the four wave mixing between the signals of said channel and control signals that repeat at a rate identical to the repetition rate of the signals of the channel and are time-aligned therewith; propagating signals of a signal stream to be demultiplexed and the control signals along a section of a polarization maintaining fiber that splits said signals into two orthogonal polarization components which are time separated, the four wave mixing being performed separately on said two components, thereby originating two individual mixing signals; feeding said two components into a section of a dispersion shifted fiber in which the separate mixing takes place; and subjecting the individual mixing signals to a reflection that causes a 90Â° rotation of their state of polarization and are sent towards a receiver by flowing again through the dispersion shifted fiber section and the polarization maintaining fiber section, that makes them join again, the pulses of the control signals having a linear state of polarization that is oriented at 45Â° to an orthogonal reference defined by a birefringence axis of the polarization maintaining fiber or an elliptical state with its major axis oriented at 45Â° with respect to said reference.