256X256 TURNOVER-TYPE FREE-SPACE MULTICHANNEL OPTICAL SWITCH BASED ONPOLARIZATION CONTROL USING LIQUID-CRYSTAL SPATIAL LIGHT MODULATORS

Free-space multichannel optical switches using polarization control ar e attracting interest for future telecommunication networks and interc onnection 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 trans parent optical switch that is also compact. A 256 x 256 multichannel o ptical switch based on the architecture is designed and fabricated. To the authors' knowledge, the channel number of the fabricated switch i s the largest yet reported among rearrangeable optical switches. Switc hing operation and signal transmission at 400 Mbits/s are performed su ccessfully with a prototype switch.