Investigation On All-Optical Regeneration Based On Self-Phase Modulation

With the development of wavelength-division multiplexing, all-optical regeneration is considered as the most important techniques in all-optical networks. All-optical regeneration based on self-phase modulation is paid more attention because it can improve the bit-error rate and Q factor and it has less impact when the environment and transmission velocity change. Furthermore, it has advantages such as strong implementation, low cost, easy extension towards the fields of multi-wavelength and so on.In this paper, the parameter and performance optimization of regenerator are investigated from single-wavelength and multi-wavelength around the regeneration scheme, which makes use of self-phase modulation in fibers and offset filter. Firstly, based on nonlinear Schrodinger equation, the principle of varieties of nonlinear effect and all-optical regeneration are analyzed. Secondly, aiming at the single-wavelength regeneration, the effect of chromatic dispersion to transfer function and Q factor improvement is discussed. The interaction between chromatic dispersion and self-phase modulation is studied and a new method is proposed to improve the plateau of transfer function by changing the fiber structure of the regenerator. Besides, the limitation of RZ-DPSK regeneration utilizing self-phase modulation is discussed. The initial conditions using four-wave mixing to achieve regeneration is given. Finally, in the multi-wavelength all-optical regeneration system, the influence of average dispersion to the performance of regenerator is discussed. A new dispersion management optimization method is proposed to overcome the degradation of performance stability of regenerator caused by the dispersion discrepancy among different wavelengths.The conclusions are showed as follows:in the single-wavelength regenerator, the chromatic dispersion will adjust the broadened spectrum components and make the Q factor improvement diminish. The performance of regenerator is nearly unchanged when the interaction between chromatic dispersion and self-phase modulation keeps stable. By adding the proper dispersion compensating fiber among two segments of high nonlinear fiber, the plateau range of transfer function is obviously increased. The regeneration of RZ-DPSK signals can not be realized using the self-phase modulation scheme. The initial condition to achieve regeneration through four-wave mixing is as follows:on the premise of high efficiency, the wavelength of pump wave should be less than zero-dispersion wavelength. Furthermore, the interval between pump wave and zero-dispersion wavelength and the wavelength interval between signal wave and pump wave must satisfy some special relations. In the multi-wavelength regenerator based on dispersion management, the regeneration performance will be better if the average fiber dispersion is positive. Through choosing the length of dispersion compensating fiber and single mode fiber to make the dispersion curve approximately fit with the dispersion curve, the best performance of each wavelength is then available respectively. The stability for the performance of regenerator is effectively improved if the input signal power and offset of the filter are properly adjusted.