Research On All-optical 2R Regeneration Technology Based On Active Nonlinear Fiber

With the development of fiber communication network, all-optic information processing devices have play more and more important role. All-optic regenerator has become researching central issue. Making use of amplifying and nonlinearity in active nonlinear fibers, simultaneously reshaping and re-amplifying optical signal using a single active nonlinear fiber was realized. This regeneration structure is different from traditional structure of 2R regenerators. The latter one is made up of optical amplifying unit and nonlinear reshaping unit. By putting forward nonlinear coupled-mode equations based on active fibers, the regeneration properties of active nonlinear fibers has been studied thoroughly via numerical simulation. The influence of magnetism on regeneration is discussed. The main content can be listed as follows:1. A new scheme for simultaneously reshaping and reamplifying optical signal using a single active nonlinear fiber was put forward. According to the four-wave mixing(FWM) coupled-mode equations of guided optical wave pulses in active nonlinear fibers, the input-to-output power transfer functions(PTFs), dependent on the gain distribution in fibers, were calculated by the symmetrical split-step Fourier algorithm. A method for evaluating all-optical 2R regeneration performance, in terms of three characteristic points of the PTF, was also presented. For the forward gain-pump case, it is shown that, the increase of pump power can effectively improve the saturated gain and reduce the input threshold power of space/mark signals; both the saturated gain and the input threshold power of space/mark signals increase with the fiber length. The conclusions above-mentioned are useful for the design of the all-optical 2R regenerators based on active nonlinear fibers.2. According to the magneto-optical nonlinear coupled-mode equations for guided optical pulses, the influence of power gain distribution on self-phase-modulation(SPM)-induced spectrum broadening is calculated by using the split-step Fourier method and the calculation results are in good agreement with the Opti System simulations. The input saturation power of the SPM-based regenerators is reduced with the increase of gain pump power, fiber length, or Erbium ion density, and then leads to the improvement of the saturation gain. Under the applied magnetic field along the axis of the active fibers, the resulting regenerators have a larger tolerance to the amplitude fluctuation for input mark pulses, and the power transfer function of regenerators can flexibly match with the input degraded signals due to the magnetic control mechanism of SPM-induced spectrum broadening.3. According to the self-phase-modulation-based spectrum broadening property of guided optical pulse in magneto-optic(MO) nonlinear fibers, we put forward a new method for magnetic field measurement using the MO nonlinear effect and introduce the concept of magnetic-field dependent loss(MDL) for improving the sensitivity to magnetic field. Research results show that, when the MO coupling coefficient is less than 0.15rad/m, the peak MDL is approximately proportional to the MO coupling coefficient and the magnetic field sensitivity is dependent on the peak power of input optical pulse. In contrast, the sensitivity of MDL to large magnetic field is poor, whose response curve’s shape is seriously influenced by peak power of input optic pulse As a result, using MDL to measure magnetic field is totally feasible.