PURPOSE: To enable the spatial sepn. of respective channels of a signal eight pulse train subjected to time division multiplexing by utilizing a function capable of spatially separating these channels by the nonlinear interference of ultra-high speed light pulses with each other within an abnormal dispersion medium.

CONSTITUTION: The signal light pulses subjected to time division multiplexing are partly inputted to a synchronizing device 12 and the remains are made incident on the input port A of the abnormal dispersion medium 13. A control light pulse generator 14 outputs the control light pulses synchronized with the channels separated according to the frame period of the signal light pulses. These control light pulses are made incident at a prescribed incident angle on the input port B of the abnormal dispersion medium 13 and are emitted from an output port C. The signal light pulses entering from the input port A of the abnormal dispersion medium 13 are emitted from an output port D (E). The signal light pulses and control pulses propagating in the abnormal dispersion medium 13 are so set that propagation paths intersect with each other at a prescribed angle in the medium 13. The signal light pulses coinciding with the control light pulses in time are spatially separated in such a manner.