All-Optical Multi-Level Phase Quantization Based on Phase-Sensitive Amplification With Low-Order Harmonics

A novel scheme is proposed for all-optical multilevel phase quantization by mixing two lower-order harmonics, rather than mixing the signal with its conjugate (M - 1)th harmonic, which is difficult to be generated but necessary for the traditional quantization method. The low-order harmonics used in the proposed scheme are determined as the conjugate (M/2 - 1)th and the (M/2 + 1)th harmonics for M = 4n, or the conjugate (M/2 - 2)th and the (M/2 + 2)th harmonics for M = 4n + 2, or the conjugate [(M - 1)/2]th and the [(M + 1)/2]th harmonics for M = 2n + 1, n = 1, 2, 3 . . .. The simulations show the effectiveness of the scheme for the eightand nine-level all-optical phase quantization. Furthermore, the application of the scheme to the all-optical phase regeneration is validated. An improved method with two cascading stages is also proposed and validated to achieve a monotonic step-like phase- phase transfer characteristic for the optimized all-optical phase quantization. This proposed scheme provides a new way for multilevel phase quantization and multi-level phase shift keying regeneration to meet the ever increasing demand for the bandwidth in fiber-optic communication.