Phase Regeneration of QPSK Signal in SOA Using Single-Stage, Wavelength Converting PSA

Abstract

Abstract-We demonstrate, for the first time, all-optical phase regeneration of a quaternary phase shift keying (QPSK) signal through phase sensitive amplification (PSA) in nonlinear semiconductor optical amplifiers (SOAs), using a scheme only previously demonstrated in highly nonlinear fibre (HNLF). We make use of a highly tunable phase quantising scheme to circumvent some of the limitations imposed by the use of SOAs and show that it may function in either a conjugating or non-conjugating manner.

Full quadrature regeneration of QPSK signals using sequential phase sensitive amplification and parametric saturation

“…As previously mentioned, the present demonstration can be considered to be an instance of the two stage amplitude regenerator demonstrated in [11], with the first, wavelength converting stage replaced by the idler-free, wavelength converting phase regenerator demonstrated in [12,13]. Hence, the complete system can be described by its two underlying subsystems: a wavelength converting idler-free PSA (upper yellow section of Fig.…”

“…The first stage in that demonstration was chosen to be a simple, degeneratepump wavelength converter, although it was discussed that this first stage could be replaced by any scheme capable of imparting SPM upon the signal. In the present demonstration, we do exactly this, and replace the first stage with a wavelength converting PSA-based, 4-level phase regenerator [12,13]. This results in a system which uses only two nonlinear stages to achieve both phase and amplitude regeneration and highlights the benefits of exploiting conjugation between stages to compensate their intrinsic SPM.…”

“…The wavelength converting idler-free scheme used herein works analogously, but instead functions by coherently adding the conjugate of the signal to its unconjugated 3rd harmonic [12,13]. Figure 1(a) shows the input of the nonlinear medium used to perform phase regeneration upon the signal.…”

“…As there is only one process which relies upon P2, the generation of conjugated signal photons, by controlling the power with which it enters the nonlinear medium, we may easily control the mixing factor, m, and hence the amount by which the phase of the signal is squeezed (in fact, m may be controlled by varying any of P1, P2 or S [12,13]). By using a mixing factor of m = 1/3, we can achieve a flat-topped phase transfer profile [15].…”

Optical Phase Conjugation Using Nonlinear SOA for Nonlinearity and Dispersion Compensation of Coherent Multi-Carrier Lightwave Systems

“…Semiconductor optical amplifiers (SOAs) are excellent alternatives, where nonlinearities are initiated with pump power levels as low as 0 dBm [21]- [23]. The SOAs are proven to have better energy efficiency, have a smaller footprint, and supports on-chip-integration, thus making it a propitious candidate for all-optical signal processing operations.…”