Optical digital-to-analog conversion based on weighted fiber coupler

The scheme of optical digital-to-analog conversion based on weighted fiber coupler is proposed. The simulation results show that when the output signal without filter, the time domain waveform is interfered by beat noise, and the function of optical digital-to-analog conversion cannot be realized. Fortunately, the beat noise is concentrated in the high frequency region which is more than 100GHz by setting the wavelength interval of the directly modulated laser array, and it can be removed effectively by the low-pass filter. However, some peak interference will appear at the time of signal alternation. When the filtering processing matching with the bandwidth of the transform signal, the peak interference can be suppressed. Finally, the optical digital-to-analog conversion with signal rate of 10Gbps and quantization accuracy of 5 bits can be realized.