Polarization scrambler, optical add/drop multiplexer, optical route switching apparatus and wavelength division multiplexing optical transmission system

An optical add/drop multiplexer comprising:

• a demultiplexing unit for demultiplexing a signal light into wavelength components, and being able to output at least one of the wavelength components through a drop port;
• a multiplexing unit being able to be inputted thereto at least one of the demultiplexed wavelength components through a through port, multiplex the wavelength component inputted through the through port and at least one wavelength component inputted through an add port together into a wavelength division multiplexed signal light, and output the wavelength division multiplexed signal light;
• and
• at least one polarization scrambler for rotating a polarization state of a corresponding one of the wavelength components to be multiplexed together into the wavelength division multiplexed signal light by said multiplexing unit and to be outputted therethrough;
• said polarization scrambler comprising:
• a polarization state rotating unit for rotating the polarization state of the wavelength component to be outputted through said multiplexing unit;
• and
• a rotation speed controlling unit for controlling a rotation speed of the polarization state of the wavelength component in said polarization state rotating unit on the basis of a speed and scheme of modulation of the wavelength component and a value of polarization mode dispersion of a transmission path on which the wavelength component is to be transmitted.

An optical route switching apparatus having a plurality of input ports and a plurality of output ports, selectively directing a route of each of wavelength components of a wavelength division multiplexed signal light inputted from each of said plural input ports to an arbitrary one of said plural output ports, multiplexing wavelength components led to each of said output ports together into a wavelength division multiplexed signal light, and outputting the same from said output port, said optical route switching apparatus comprising:

• at least one polarization scrambling apparatus disposed at a position of at least one of said input ports or at least one of said output ports of said optical route switching apparatus, said polarization scrambling apparatus being able to rotate a polarization state of at least one wavelength component of the wavelength division multiplexed signal light;
• said polarization scrambling apparatus comprising:
• a provisional demultiplexing unit for demultiplexing the wavelength division multiplexed signal light into a plurality of output streams of respective wavelength components;
• at least one polarization scrambler disposed over one of the output streams, said polarization scrambler rotating the polarization state of a corresponding wavelength component of the signal light demultiplexed by said provisional demultiplexing unit;
• and
• a combining unit for combining the output streams;
• said polarization scrambler comprising:
• a polarization state rotating unit for rotating the polarization state of the wavelength component of the signal light from said provisional demultiplexing unit;
• and
• a rotation speed controlling unit for controlling a rotation speed of the polarization state of the wavelength component by said polarization state rotating unit on the basis of a speed and scheme of modulation of the wavelength component, and a value of polarization mode dispersion of a transmission path on which the wavelength component is to be transmitted.

A wavelength division multiplexing optical transmission system having, on a transmission path, an optical add/drop multiplexer having a demultiplexing unit being able to demultiplex a signal light into wavelength components and output at least one of the wavelength components of the signal light through a drop port, and a multiplexing unit being able to multiplex at least one arbitrary wavelength component inputted through an add port and the demultiplexed wavelength components together into a wavelength division multiplexed signal light and output the wavelength division multiplexed signal light, said wavelength division multiplexing optical transmission system comprising:

• said optical add/drop multiplexer comprising:
• at least one polarization scrambler for rotating a polarization state of a corresponding one of wavelength components of a signal light to be outputted through said multiplexing unit;
• said polarization scrambler comprising:
• a polarization state rotating unit for rotating the polarization state of the wavelength component of the signal light to be outputted through said multiplexing unit;
• and
• a rotation speed controlling unit for controlling rotation speed of the polarization state of the wavelength component of the signal light by said polarization state rotating unit on the basis of a speed and scheme of modulation of the wavelength component of the signal light, and a value of polarization mode dispersion of a transmission path on which the wavelength component is to be transmitted.