Photonic techniques have potential to overcome the limitations of electronic digital-to-analog conversion. A serial optical DAC, using fiber dispersion with optical weighted wavelength multiplexing, is proposed and demonstrated. Serial Digital codes are overlapped regularly in time domain due to dispersion-based delays. Intensity information for the conversion is extracted by synchronous gating pulse train. The system is operated with a high precision time control. Performance of the ODAC is experimentally investigated by establishing a 4-b 12.5 Gb/s system. The linear transfer function is described and an ENOB of 3.55 is obtained. The proposed architecture could be easily modified for better performance.

A dual photonic-delay line cross-correlation method for phase noise measurement of microwave signal based on dense wavelength division multiplexing (DWDM) is proposed and experimentally demonstrated. The kilometer-long delay fiber is used together by the two mutual independent channels through the DWDM technology, resulting in that it is easier to control the kilometer-long fibers of the two channels are same. And it reduces the cost of the system by reducing the use of several kilometers of fiber and a Mach-Zendher modulator (MZM). Then, it uses variable optical fiber delay lines (VOLDs) to replace the electronic phase shifters, and a broader operation bandwidth can be obtained. A lower phase noise floor has been obtained by more averaging of the cross-correlation spectrum. In the experiments, the phase noise of a 10-GHz microwave signal has been measured accurately. A large operation bandwidth of 4-11 GHz is achieved and a measurement phase noise floor of -152.6 dBc/Hz at 10 kHz offset at 10 GHz in a 20 's delay measurement system is realized by averaging 100 times.