Experimental demonstration of arbitrary waveform generation by a 4-bit photonic digital-to-analog converter

Arbitrary waveform generation by a serial photonic digital-to-analog converter (PDAC) is demonstrated in this paper. To construct the PDAC, an intensity weighted, time and wavelength interleaved optical pulse train is first generated by phase modulation and fiber dispersion. Then, on-off keying modulation of the optical pulses is implemented according to the input serial digital bits. After proper dispersion compensation, a combined optical pulse is obtained with its total power proportional to the weighted sum of the input digital bits, and digital-to-analog conversion is achieved after optical-to-electronic conversion. By properly designing the input bits and using a low pass filter for signal smoothing, arbitrary waveforms can be generated. Performance of the PDAC is experimentally investigated by establishing a 2.5 GSa/s 4-bit PDAC. The established PDAC is found to have a good linear transfer function and the effective number of bits (ENOB) reaches as high as 3.49. Based on the constructed PDAC, generation of multiple waveforms including triangular, parabolic, square and sawtooth pulses are implemented with the generated waveforms very close to the ideal waveforms.