Patent ID: 7386012

Claim:
An optical communication system for transmitting optical signals transmitted on a plurality of first optical transmission lines to a plurality of third optical transmission lines via a second optical transmission line, comprising: a first optical transmission unit connected to said first and second optical transmission lines, for receiving first optical signals transmitted on said first optical transmission lines and transmitting a second optical signal obtained from said first optical signals to said second optical transmission lines; and a second optical transmission unit connected to said second and third optical transmission lines, for receiving said second optical signal from said second optical transmission line and transmitting third optical signals obtained from said second optical signal to said third optical transmission lines, wherein said first optical transmission unit extracts optional information included in first regions of a plurality of first overheads of said first optical signals and enters said optional information extracted into a second region which is not defined for a particular use in a second overhead of said second optical signal and transmits said second optical signal comprising said optional information in said second overhead to said second transmission lines; and said second optical transmission unit extracts said optional information in said second overhead of said second optical signal and enters said optional information extracted into third regions of a plurality of overheads of third optical signals and transmits said third optical signals comprising said plurality of optional information in said third overheads to said third transmission lines, wherein said first regions are predetermined for storing said optional information in said first overheads, and said third regions are predetermined for storing said optional information in said third overheads.