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

Abstract

A novel scheme is proposed for all-optical multi-level phase quantization by mixing two lower-order harmonics, rather than mixing the signal with its conjugate $(M\,{-}\,1)\text{th}$ 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 $(M/2\,{-}\,1)\text{th}$ and the $(M/2\,{+}\,1)\text{th}$ harmonics for $M=4n$ , or the conjugate $(M/2-2)\text{th}$ and the $(M/2+2)\text{th}$ harmonics for $M=4n+2$ , or the conjugate $[(M\,{-}\,1)/2]\text{th}$ and the $[(M+1)/2]\text{th}$ harmonics for $M=2n+1$ , $n=1,2,3\ldots$ . The simulations show the effectiveness of the scheme for the eight- and 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 multi-level phase quantization and multi-level phase shift keying regeneration to meet the ever increasing demand for the bandwidth in fiber-optic communication.