Optical Dynamic RAM for All-Optical Digital Processing

The concept of a novel solution for an n-bit all-optical dynamic random access memory for advanced functionalities in all-optical digital processing is investigated. The scheme is composed of a matrix of 1-bit memory elements, each one obtained by an all-optically controlled variable optical buffer. The buffer is implemented by a wavelength preserving semiconductor optical amplifier-based fiber loop in which cross-gain modulation nonlinear effect allows for polarization and wavelength-independent operation in the whole C-band. The cell enabling command, as well as the read and write control signals, are obtained through all-optical logic operations between the row and column selecting signals. True dynamic and asynchronous random access properties, including write, read, and refresh operations, are verified for the single memory cell in terms of extinction ratio (ER) as a function of the storage time. A 1.77-μs reading delay is demonstrated without signal degradation. Multicell performance is also investigated. For an 8 × 8 matrix structure, the ER is reduced by 3 dB. A multiregister matrix for synchronous operation can be also implemented once n-bit packets are stored in each specific cell.