An optical digital-to-analog converter with a built-in intensity converter consisting of silicon waveguide

Optical digital-to-analog converters (DACs) are key to overcoming the enormous power consumption caused by the slowdown of Moore's Law. In previous work, an optical DAC consisting of a signal generator and an intensity converter was presented. The generating component was integrated into the device, but a higher level of device integration is desirable. An optical DAC device with a built-in intensity converter for a 2-bit binary phase-shift keying (BPSK) signal is demonstrated. The integrated device consists of two delay line interferometers (DLIs) with silicon waveguides. The first is used to generate a quadrature PSK (QPSK) signal from two BPSK signals, and the second is used to convert the QPSK constellation into light intensities. Experimental results show that the 2-bit digital codes 00, 01, 10, and 11 can be successfully converted into four different light intensities depending on their pattern at 10 Gbps.