Constant Power Constellation Grouping for Reducing Nonlinearity Effects in Fiber Optics

Abstract

Fiber nonlinearity is the main obstacle for increasing the capacity of existing fiber systems. This nonlinearity depends on the accumulated power launched into the wavelength division multiplexing (WDM) channels. In this article, we model the accumulated launched power and show the impact of the constellation design on the fiber nonlinearity. We analytically show that one can achieve the same noise power at longer distances by controlling the fluctuations in the launched power. We then propose the idea of constant power constellation grouping (CPCG) to control the power fluctuations and achieve significantly better system reach compared to conventional quadrature amplitude modulation (QAM) constellations. In comparison with constant power phase-shift keying (PSK) constellations, we achieve much higher data rates for the same signal to noise ratio (SNR). Our simulation study confirms our theoretical findings and demonstrates the benefits of the proposed CPCG method.