Power Transfer Characteristic Of All-optical2R Regenerator

The process to realize reshaping and re-amplification of deteriorated signals in theoptical domain is called all-optical2R regeneration （2R, Reshaping andRe-amplification） in the optical fiber communication system, which is considered as animportant technology applied to the high speed all-optical network in the future. The"S" shape power transfer function（PTF, Power Transfer Function）can represent thepower relationship of input and output signals in all-optical regeneration, which is animportant method can be used to characterize the effect of signal regeneration. In thispaper, from theoretical analysis to software simulation verification, the power transfercharacteristic of2R all-optical regenerator has been researched thoroughly, the maincontent can be listed as follows:1. The influences of fiber loss and pump depletion on single-pump four wavemixing （FWM） parametric process in the isotropic and highly-nonlinear optical fiber areconsidered. The power conversion relationship of the guided optical waves is expressedby an elliptic equation, and the calculated result is consistent with the simulation dataobtained by OptiSystem software. The elliptic equation is also used to analyze theperformance of all optical2R regenerators based on four-wave mixing. The researchshows that the increase of fiber loss coefficient can not only deteriorate there-amplifying performance, but also lead to the decrease and increase of noise tolerancelimits of input signal in high and low levels, respectively.2. According to the linearized three-section model of input/output power transferfunction （PTF）, the theoretical assessment method of all-optical reshapers’ performanceis investigated and verified by simulation of four-wave-mixing based scheme. Theperformance of all-optical reshapers depending on the input signal of Gaussiandistribution is analyzed. The transfer function is divided into five regions from low tohigh power levels, and a larger improvement of Q factor or BER performance canbe obtained for the cases that the average level of mark pulses exists in the fifth region.With the increase of the PTF’s second-section slope for an optimum reshaper, the gainsaturation of Q factor or BER performance will occur and the extinction ratio will be improved linearly.3. Two all-optical regeneration schemes based on four-wave mixing are compared.Under the condition of data-pump modulation scheme of all-optical regeneration, wecan use idler analytic formula without considering pump consumption to analyze thepower transfer function’s slope, namelyS_PTF. We also use the analytic formula ofS_PTFto analyze the relationship between signal wavelength and fiber dispersion. Thestudy shows that gain bandwidth can limit theS PTFto infinitely increasing. Theimprovement of the input signal power cannot change the value ofS_PTF,min, while it canachieveS_PTFoptimization in the fixed wavelength range. By carefully analyzing, wediscover that the value ofS_PTF,maxincreases as the length of fiber becomes large.Besides, the value ofS_PTF,maxincreases a little when fiber dispersion slope grows.Meanwhile, when the fiber length is much larger, this increasing trend graduallybecomes relatively more obvious.