Photonic Analog-to-Digital Conversion using LiNbO_3 Asymmetric Mach-Zehnder Interferometer

摘要

Asymmetric lithium niobate Mach-Zehnder interferometer and its applications in photonic analog-to-digital conversion will be discussed. Two schemes based on the asymmetric interferometer will be proposed and analyzed. The first scheme is the phase shift photonic analog-to-digital conversion using asymmetric interferometer and synchronized multi-wavelength optical sampling pulses. Because of the dispersion effect of the lithium niobate crystal, when multi-wavelength optical pulses enter into the interferometer, at the output port, different wavelengths will have different phase differences between two arms. As a result, after interference, the transmission characteristics of different wavelengths will have a phase shift between each other, and this is just the key issue of phase shift photonic analog-to-digital conversion. The other scheme we will propose in this paper is a spectral encoded photonic analog-to-digital conversion. The spectral transmission characteristic of the asymmetric interferometer will shift with the voltage change of the analog signal, and this shift has an ideal linear relation with the analog voltage change. The peak wavelength of the transmission spectrum can be detected to realize quantization of the applied analog signal. Using both schemes presented in this paper, high sampling rate and high resolution optical analog-to-digital conversion can be realized.