3R regeneration of a 40-Gbit/s optical signal by optical parametric amplification in a highly-nonlinear fiber

40 Gb/s all-optical regeneration based on the pump depletion effect in fiber parametric amplification

“…That means that phase variations will not exceed 45 degrees after each regeneration stage. On the contrary in a typical parametric limiter [4][5][6] this does not happen as mentioned before. In each regeneration stage the power-dependent phase shift is added to the already existent signal phase and unavoidably the phase fluctuations increase with the distance and the number of the regenerators.…”

“…Fiber-based techniques are recognized as potential candidates for the implementation of all-optical regenerators as the underlying nonlinear mechanism of Kerr effect is extremely fast providing the possibility of supporting ultra-fast signals. Parametric process relying on four-wave mixing (FWM) in dispersion shifted fibers (DSFs), is one of the fiber-based techniques theoretically proposed and experimentally demonstrated as a possible candidate for optical regeneration purposes [1][2][3][4][5]. All the proposed schemes refer to fiber-optic parametric amplifiers (FOPAs) operating in the saturation regime and are designed mainly for intensity modulated signals.…”

“…[4] the reshaping process is accomplished at the signal wavelength exploiting the properties of extremely fast gain saturation in FOPAs, and in Ref. [5] the authors are based on the same reshaping principle, also providing the retiming function by utilizing a clockmodulated pump wave.…”

“…[3] is for the same reason problematic, since the pump phase fluctuations will be doubled when transferred to the idler wave carrying the reshaped data. The reshaping techniques of [4,5] rely on the saturated parametric amplification at the signal wavelength and thus are not subject to this detrimental effect. Although the saturated amplification provides amplitude stabilization for symbol "1," it can not offer noise suppression at "0" and extinction ratio enhancement.…”

“…In the same section a comparison analysis between the proposed scheme and the regenerators of Refs. [5,6] by means of Qfactor calculations is also carried out. Finally, conclusions on the present work are given in Section 6.…”