Current optical communications systems require high-speed logic for routing and regeneration of signals, as well as for higher-level functions such as encryption and decryption. At present, these functions are performed by converting the optical signal to the electronic domain for processing, and then generating a new optical signal. To perform these functions optically, an all-optical integrated logic must be developed. To be useful, this optical logic must have the following characteristics.

• High speed ( i.e., faster than a comparable electronic switch). This means it must operate at speeds greater than at least 50 Gb/sec.
• Full Boolean logic capability. This simply means the optical logic technology must be capable of performing the complete set of Boolean logic functions.
• Cascadability. This means that the output of the logic gate must be able to be used as the input for the next stage of logic gates. With amplification, it must be capable of fanning out to provide input to multiple logic gates.
• Capability of high-density integration. For this, the individual gates must be small and the waveguide technology used must allow small radius bends so that the gates can be interconnected in a small area.