Wavelength Sampling and Quantizing Optical ADC Based on Long-Period Waveguide Grating Filter

We present a novel optical wavelength sampling and quantizing method that can be used for photonic analog-to-digital converters. The wavelength sampling is realized by using a high-speed optical tunable filter. The tunable filter has long-period-waveguide-grating structure, and is controlled by an analog electronic signal. The output wavelength of the optical filter is determined by the amplitude of the analog electronic signal. Different amplitude leads to the optical filter outputting different wavelength. An arrayed waveguide grating separates the different wavelength into different spatial channel to complete wavelength quantizing function. At the output of the spatial channels, a detector array is used to realize the coding function. The utilization of wavelength sampling and quantizing allows the analog-to-digital converter to achieve high resolution because the sampling and quantizing are carried out in the wavelength domain, which is immune to the intensity noise and disturbance. The limits on sampling rate and quantization resolution are investigated in detail. The analysis results are shown that our analog-to-digital converter scheme is promising to achieve high-resolution of 8 bits at the sampling rate of 10 GS/s.