Optical clock signal distribution system in WDM network

An optical clock distribution system in a WDM network comprising:

• a first clock signal source and a second clock signal source generating a first clock signal and a second clock signal respectively having PRC (Primary Reference Clock) level;
• a first optical clock generator and a second optical clock generator respectively converting clock signals being output from said first clock source and said second clock source into optical clock signals having a first wavelength and a second wavelength;
• a first optical transmission line and a second optical transmission line transmitting optical clock signals respectively having said first wavelength and said second wavelength being output from said first optical clock generator and said second optical clock generator;
• and
• a wavelength-demultiplexer provided in a unit of said network, wavelength-demultiplexing said optical clock signals having said first wavelength and said second wavelength,
• wherein, further by comprising a clock signal selector provided in said unit of the network for selecting a wavelength-demultiplexed optical clock signal having either said first wavelength or said second wavelength, a redundant configuration of said optical clock distribution system is attained.