PURPOSE: To reduce the scale of an exchange by decreasing the scale of the exchange depending on the presence of a directly coupled channel and applying demultiplexing/multiplexing of a data signal of an exchange close to the destina tion into the same optical frequency to the utmost.

CONSTITUTION: When the sum of internal idle channels of two cells with differ ent optical frequency transferred in the same direction exceeds number of channels in one cell, the two cells are integrated into one cell. Thus, a high utilization efficiency equivalent to the packet exchange is realized.