New technique for wavelength-division-multiplexing optical switching utilizing the mode-hopping phenomenon of semiconductor lasers in the visible wavelength region

We have demonstrated a novel WDM and self-routing scheme as well as electro-optical logic-gate operations based on the mode-hopping phenomenon previously considered as a cause of bad noise in the Fabry-Perot type semiconductor lasers. In our routing scheme, data signals can be sent through adequate routes because they have information on their own destinations assigned by hopped wavelengths in their carrier light wave form a laser diode. The hopped wavelength can be controlled by only switching temporarily the d.c. bias levels of the driving current of the laser diode. The performed speed of the 1XN channel wavelength-switching was estimated at about 167 nanoseconds, limited by insufficiencies in our electronics, not by the phenomenon itself. The number of destination channels 'N' has been limited to the number of allowed hopping modes in the sample laser diode. Since the mode-hopping phenomenon itself has been reported to be faster than nanoseconds, more efficient and ultra-fast self-routing or WDMA systems based on this phenomenon will be performed. In addition, we have performed electro-optical logic-gate operations by modulating the injection current of the laser diode through mode-hopping regions. The achieved data rate of our gate operations for AND, Ex-OR and NOR gates was typically 3 X 12 Mbit/s with two simultaneously modulated input signals.