Wavelength cross connect device, and wavelength cross connect method

A wavelength cross connect device comprising:

• a wavelength cross connect (WXC) unit comprising M input-side WSSes and M output-side WSSes mesh-connected to the M input-side WSSes;
• and
• a wavelength band switching unit,
• wherein the WXC unit is configured to receive M wavelength multiplexed signal beams, in each of which optical signals of distinct wavelength bands are multiplexed and each of which is transmitted in multiple bands in a respective one of M optical transmission lines each including one or a plurality of optical fibers,
• wherein each of the M input-side WSSes is configured to:
• receive a respective one of the M wavelength multiplexed signal beams,
• split the received wavelength multiplexed signal beam into N wavelength multiplexed signal beams, where N is a number larger than M;
• input, of the N wavelength multiplexed signal beams, wavelength multiplexed signal beams in each of which optical signals for which wavelength band conversion is not necessary are multiplexed to the M output-side WSSes mesh-connected to the input-side WSS, respectively;
• and
• input, of the N wavelength multiplexed signal beams, wavelength multiplexed signal beams in each of which optical signals for which the wavelength band conversion is necessary are multiplexed to the wavelength band switching unit, and
• wherein the wavelength band switching unit is configured to:
• perform the wavelength band conversion on each of the wavelength multiplexed signal beams input from the M input-side WSSes, each to generate a wavelength-band-converted wavelength multiplexed signal beam in which the wavelength bands of the optical signals of the distinct wavelength bands multiplexed in the wavelength multiplexed signal beam input from the M input-side WSSes have been converted to different wavelength bands, the different wavelength bands being all selected from among the distinct wavelength bands, and
• output the wavelength-band-converted wavelength multiplexed signal beam to the M output-side WSSes so as to be able to be rerouted.