The Study On Four-wave Mixing And Its Application Based On High Nonlinear Fiber

Fiber optical parametric amplifiers (FOPAs) are optical devices depending on the nonlinear response of the third-order susceptibleχ(3) which need one or two pumps. The pump wavelengthλ0 is generally tuned near the zero dispersion wavelengthλ0 as well as the phase matching condition being matched.The major advantages of FOPAs are broad bandwidth, high signal gain, able to operate at arbitrary center wavelength, idler generation(good for wavelength conversion), high-speed optical signal processing and so on .In this paper, we conduct a deep theory and experiment research concerning the parametric gain ,gain saturation, signal gain spectrum improvement and the suppression of degenerate four-wave mixing in non-degenerate optical parametric amplification. The structure of this paper is as follows:(1) Research of basic theory of fiber amplifiers. With Maxwell equations we get Nonlinear Schrodinger Equation(NLS) which describes the evolution of the lightwave in the FOPA.(2) Research of the gain parametric coefficient.We acquire the analytical expression of the parametric gain coefficient from the small-signal model, and discuss the maximum value of the parametric gain coefficient and the gain bandwidth from both one pump and two pumps. The conclusion is that the maximum value of the parametric gain coefficient and the gain bandwidth relate to wavelengths and power of the launched pump lightwave and signal lightwave.(3) Research of gain saturation characteristics of optical parametric amplifiers.In this paper, we mainly study gain saturation characteristics in non-degenerate optical parametric amplifiers by Finite Difference Time Domain method solving Nonlinear Schrodinger equation, and the conclusion is that under the same condition, the gain saturation value of double pumping optical parametric amplifiers is greater than that of a single pumping one, and gain saturation value increases with the power of launched pumping lightwave increasing, as well as decreasing with the power of launched signal lightwave increasing(4) Research into suppression of the idler in the degenerate four-wave mixing which takes place in non-degenerate optical parametric amplifiers. Due to the four-wave mixing effect which weakens the capability of the signal light amplifying in a non-degenerate optical parametric amplifier process happens between two high pumping source .In this article,we have done some researches on suppression of the idler in the degenerate four-wave mixing and the conclusion is that degenerate four-wave mixing effect can be completely suppressed by choosing proper pumping lightwave wavelength.(5) Research of the signal gain spectrum .We have analysed the model that adding a section of dispersion compensation fiber (DCF) connects to the tail of the high nonlinear fiber to improve the signal gain spectrum. Meanwhile ,we get an analytical expression of the output signal lightwave power led by the Nonlinear Schrodinger equation. On this basis ,we then have furtherly analysed another model of periodically inserting DCF into HNLF to improve the signal gain spectrum, which could be used as a pectination filter.(6) Conducting an experimental research on broadband tunable wavelength conversion based on the fiber optical parametric amplifiers. The signal wavelength is fixed nearby the zero dispersion wavelength, and the high power pump lightwave acts as a pumping source. When the wavelength of the continuous tunable laser is adjusted towards the long wavelength direction, the wavelength of the new born idler is automatically adjusted towards the short wavelength direction.