Optical bit-pattern recognition by use of dynamic gratings in erbium-doped fiber

We present a novel optical bit-pattern-recognition technique that uses erbium-doped fiber at room temperature. Counterpropagating beams write a patterned gain-depletion grating in pumped erbium-doped fiber. This grating, recorded in the erbium gain medium, can be used for correlation with other optical bit patterns. We have demonstrated correlation of arbitrary return-to-zero bit patterns of as many as 8 bits at 1 Gbit/s. Theory suggests that scaling to higher bit rates is feasible. (C) 1997 Optical Society of America.