US Patent 7561455 Memory system using single wavelength optical transmission

A controller converts a parallel command signal and address signal, or a parallel write data signal into a first serial signal, and outputs the converted signal as a first optical signal with a single wavelength to a memory device via an optical transmission line. The memory device converts the first optical signal into the original parallel command signal, address signal, and write data signal, and outputs the converted parallel signals to a memory unit. The memory device converts a parallel read data signal from the memory unit into a second serial signal, and outputs the converted signal to the controller via the optical transmission line as a second optical signal with a single wavelength. It is unnecessary to transmit the optical signal using an optical multiplexer, an optical demultiplexer, etc., thereby improving transmission rate of signals transmitted between the controller and the memory device at minimum cost.