Optical communication system and first node

A system, comprising:

• a first node;
• a second node;
• and
• an optical fiber that connects the first node and the second node, wherein a zero-dispersion wavelength (ZDW) of the optical fiber belongs to a ZDW region;
• and
• the optical fiber is configured for transmission of N first-direction wavelength channels and N second-direction wavelength channels,
• wherein N is an integer greater than 2, at least two first-direction wavelength channels and at least one second-direction wavelength channel are located in the ZDW region, or at least two second-direction wavelength channels and at least one first-direction wavelength channel are located in the ZDW region,
• the at least two first-direction wavelength channels or the at least one first-direction wavelength channel, and the at least one second-direction wavelength channel or the at least two second-direction wavelength channels, that are in the ZDW region are mixedly distributed,
• the at least two first-direction wavelength channels or the at least one first-direction wavelength channel is sent by the first node to the second node, and
• the at least one second-direction wavelength channel or the at least two second-direction wavelength channels is sent by the second node to the first node.