A novel Mach–Zehnder-interferometer regenerator for any level number of optical PAM signals using cross phase modulation of orthogonally polarized light

Abstract

We propose a novel Mach–Zehnder interferometer (MZI) regenerator structure based on cross-phase modulation (XPM) effect between orthogonally polarized light. By adjusting the optical phase shifter on one arm of the MZI, the alignment of the optimal working points of the optical regenerator with the respective level powers of the degraded optical pulse-amplitude-modulated (PAM) signal can be achieved. The input-to-output power transfer function (PTF) capable of the regenerative Fourier transform, along with the optimal working points, is derived through theoretical analysis and the simulated PTFs are consistent with the theoretical results. Our research shows that the regenerative ability (RA) of the PAM regenerator increases with the input optical signal-to-noise ratio (OSNR), and the signal gain is inversely proportional to the level interval power of the input signal. The regeneration scheme proposed in the paper can theoretically be applied to the reshaping of an infinite number of regenerative levels, with a good consistency in the regeneration performance for each level. The phase preserving and bit-error rate (BER) properties of the regenerator are taken into account as well.