256 × 256 Turnover-type free-space multichannel optical switch based on polarization control using liquid-crystal...

Free-space multichannel optical switches using polarization control are attracting interest for future telecommunication networks and interconnection networks in computers. We describe a switching architecture, the turnover type, for such free-space multichannel optical switches. The architecture makes it possible to realize a large-scale and transparent optical switch that is also compact. A 256 × 256 multichannel optical switch based on the architecture is designed and fabricated. To the authors' knowledge, the channel number of the fabricated switch is the largest yet reported among rearrangeable optical switches. Switching operation and signal transmission at 400 Mbits/s are performed successfully with a prototype switch.