Fig. 1. Operating principle of the proposed PLA based on parallel spectrum modulation. (a) Sketch map of a three-input PLA. (b) The correspondence matrices between the states of input signals and wavelengths. SM, spectral modulator; WSS, wavelength-selective switch; OS, optical switch; WS, wave shaper.

Fig. 2. Performance characterization of the PLA. (a) Schematic diagram for the proposed PLA. (b) Measured confusion matrix between 256 input states and output power of 256 wavelength channels. (c) Output spectra of PLA for three different minterms. (d) Schematic diagram of the 4-bit comparator and the corresponding power distributions of three output ports between input signal A $({\mathrm{A}}_1{\mathrm{A}}_2{\mathrm{A}}_3{\mathrm{A}}_4)$ and signal B $({\mathrm{B}}_1{\mathrm{B}}_2{\mathrm{B}}_3{\mathrm{B}}_4)$. Input/output waveforms and output eye diagrams of the comparator in the situations of (e) A₂A₃A₄ < B₂B₃B₄, (f) A₂A₃A₄ = B₂B₃B₄, and (g) A₂A₃A₄ > B₂B₃B₄.

Fig. 3. Demonstration of nine-input PLA. (a) Nine-input PLA realized by combining the wavelength’s and spatial dimensions. (b) Statement machine to infer the date (month and day) according to the provided day of the year based on nine-input PLA. The input is 324th (101000100) of the year, and the output is November (1011), 20 (10100). (c) A reverse statement machine to infer the day of the year according to the provided date (month and day). The input is March (0011), 30 (11110), and the output is the 89th (001011001) day of the year. OC, optical coupler.

Fig. 4. Operation of Conway’s Game of Life on general optical CA computing platform. (a) Schematic for the evolution of Conway’s Game of Life executed by nine-input PLA. The evolutionary rules of Conway’s Game of Life,³⁰ in which the two different colors represent the state of the cell (blue represents the live state and white represents the dead state), are programmed into nine-input PLA. The input of PLA is the states of the center cell and surrounding eight cells, and the output is the center cell’s state of the next iteration. (b) Three basic models in Conway’s Game of Life,⁴⁶ including still life (from left to right: block, boat, beehive, and long snake), moving object (glider and light spaceship), and oscillator (pulsar). (c) Complex models of glider gun and breeder implemented by nine-input PLA.

Fig. 5. Other kinds of 2D CAs implemented by the PLA. (a) The replicator-like evolution, in which the smile face copies itself in the iteration process. (b) The nonisotropic evolution, in which a single-cell pattern can create the Sierpinski triangle.

Table 1. Comparison between the proposed PLA and existing methods.