Study On High-Speed All-Optical Wavelength Conversion Technology Based On Cascaded Second-Order Nonlinear Processes

All-optical wavelength converter is one of the core devices in future optical networks. It will play key role in DWDM optical communication networks. All-optical wavelength conversion based on cascaded second-order nonlinearity in quasi-phase-matching(QPM) optical waveguides is a very promising optical wavelength conversion technology, processing many unique advantages such as strict transparency to the rate and modulation format of signals, multiple channels simultaneous conversion ability, very low noise figure etc. Theoretical and experimental research on Second-harmonic Generation and Difference-frequency Generation(SHG+DFG) in a periodically poled Lithium-Niobate waveguide is presented in this paper. The main contents are as follows:(1) The important applications of AOWCs in future optical communication systems and several usual types of AOWCs are addressed. The principles and latest research progresses of SHG+DFG-AOWC are introduced.(2) The theoretical model of SHG+DFG-AOWC is built based on nonlinear optics and optical waveguide theories, and the nonlinear couple-mode equations describing the optical wavelength conversion in QPM waveguide are derived. Furthermore, the parameters which affect the wavelength conversion efficiency such as the length of waveguide, wavelength of pump, wavelength of signal, power of pump, power of signal, pulse width of pump are numerically calculated and analyzed. Multi-wavelength simultaneous conversion and tunable capability are also analyzed.(3) SHG+DFG optical wavelength conversion based on a periodically poled Lithium-Niobate waveguide is experimentally researched. Two different experimental schemes are designed and demonstrated. The self-pumping scheme tunable ring cavity structure are used. Good experimental results of both the single-wavelength conversion and multi-wavelength simultaneous conversion and tunable capability are obtained.