All-optical Wavelength Conversion Based On The Cascaded Sun-and Difference Frequency Generation

First, Introduced one of the core devices in future optical networks——All- optical wavelength converter(AOWC), analyzed the based requirements of the AOWC. Then discussed several Introduced several kinds of all-optical wavelength converter based on Semiconductor Lasers, Semiconductor Optical Amplifier and Nonlinear Optical Loop Mirror. Then put forward the AOWC studied in this paper——the wavelength conversion based on the cascaded sum- and difference frequency generation (SFG+DFG) in quasi-phase- matched (QPM) periodically poled LiNbO3 (PPLN) waveguides, The main contents are as follows:Theory study: First put forward the spring-model of the nonlinear polarization, which showed the principle of the polarization visually. Then educed the nonlinear instantaneous coupling-wave equation of the cascaded sum- and difference frequency generation begin with the Maxwell and the Physical equations. Last, discussed the key technology in the PPLN——quasi-phase-matched (QPM), and compared with the birefraction, and analyzed the advantages of the QPM.Numerical simulations: First calculated the range of the QPM wavelength of the cascaded sum- and difference frequency generation, which empowered in the range of the phase mismatch. Then did some calculations of the wavelength conversion under pulse-pump and continuum-pump: Calculated the evolutions of the conversion efficiency with the PPLN; Analyzed the effect to the wavelength conversion by the pump wave power, the space between the two pump waves, the width of the pump and the depart of the waves; Calculated the tunable range of the signal wave and generated wave; And calculated the pulse-width of the generated wave.Experiment study: The pump waves were the continuous light produced by the tunable fiber ring laser, which constituted by the EDFA, PC, PPLN, coupling devices, tunable filters and tunable attenuator, and the signal wave was the tunable pulsed laser, the velocity of which was 40Gbit/s. Measured the conversion efficiency of the wavelength conversion based on the cascaded sum- and difference frequency generation; Checkout the tunabity of the signal wave and generated wave; Measured the 3dB width of the pump, and the stability of the wavelength conversion.