A Channel Model to Deal with Distributed Noises and Nonlinear Effects in a Fiber System with Distributed Raman Amplifiers

Yao Xie,You Wang,Wei Li,Qiang Zheng,Qiguang Feng

doi:10.3390/app10010133

Abstract

Nowadays, the distributed fiber Raman amplifier (FRA) has become more and more popular in long-haul fiber systems, owing to its lower noise figures and weaker nonlinear effects in the link. The critical issue in distributed FRAs is the presence of various kinds of noises and their interactions with the signal. However, the existing Raman channel models and their numerical solving methods can only partially describe how the randomly distributed noises interact with the signal. This causes the difficulties in analyzing the distributed FRA precisely and the inconveniences for the applications and the maintenance of FRA systems. In this paper, we propose a modified Raman channel model to describe more comprehensively the interactions between the distributed noises and the signal under the influence of loss, distributed gain, dispersion, and nonlinear effects in the distributed FRA systems. With the comparisons of the error–vector magnitude (EVM) curves, our model can get lower errors in the experimental results regarding bidirectional pumped FRA single-span fiber systems and multi-span systems with backward-pumped FRAs.

Highlights

Distributed fiber Raman amplifiers (FRAs) have been regarded as a key technique to achieve high-speed, high-capacity, and long-haul optical transmission systems, owing to their lower noise figures, weaker fiber nonlinear effects, and wider range of amplification characteristics, when compared with Erbium-doped fiber amplifiers (EDFAs) [1,2,3,4]
One of the main challenges for distributed FRAs is the presence of randomly distributed noises, such as spontaneous Raman scattering (SpRS) noise, double Rayleigh backscattering (DRB) noise, and relative intensity noise (RIN) transfer between the pump and the signal lights [9,10,11,12,13]
In this paper, referring to the simplified nonlinear Schrödinger equation (NLSE) neglecting pump depletion and the coupled intensity equations of Raman scattering, we propose a novel modified Raman channel model, which describes the propagation of optical signals in fibers governed by a multitude of simultaneous linear and nonlinear phenomena

Summary

Introduction

Distributed fiber Raman amplifiers (FRAs) have been regarded as a key technique to achieve high-speed, high-capacity, and long-haul optical transmission systems, owing to their lower noise figures, weaker fiber nonlinear effects, and wider range of amplification characteristics, when compared with Erbium-doped fiber amplifiers (EDFAs) [1,2,3,4]. Distributed FRAs have been extensively applied in long-reach unrepeated transmission to provide a cost-effective solution capable of transmitting a high capacity over distances of several hundred kilometers without any in-line active elements [5,6]. Raman amplification plays an important role in random feedback fiber lasers [7] and ultra-long-reach distributed sensing [8]. The interactions between the signal and these noises with nonlinear effects are more complex than those of lumped EDFA systems.

Methods

Findings

Discussion

Conclusion