Nonlinear equalizer for coherent OFDM optical systems

Abstract

Given the exponential increase of data rates demand in the recent years, optical communications offers an attractive solution due to several advantages when compared with wireless communications, some of them are unlimited bandwidth and low losses for long distances communications, due to those advantages optical networks have become a natural choice for supporting ever-increasing broadband services for future high-speed networks like 5G and 6G networks. This document consists of six chapters covering various topics related to optical communication networks including characteristics, challenges, and novel algorithms permitting to improve the optical network performance. As a start, an introduction for a general perspective of the dissertation is presented in chapter I and the definition of different concepts of optical networks are presented in Chapter II, in this chapter the concept of passive optical network (PON), Orthogonal frequency multiplexing (OFDM) and other concepts that are important to understand are described. In Chapter III, the concept of elastic optical network is defined and the problem of routing and spectrum allocation (RSA) in elastic optical networks is defined, in this chapter an exhaustive review of the state of the art to solve the RSA problem is presented with a summary of key parameters that need to be taken into account for optical networks under different topology. An innovative method to mitigate the optical nonlinearities of long haul coherent optical networks is presented in Chapter IV. The presented method is an improvement in the state of the art, the method uses the Hammerstein model to describe mathematically the optical fiber link and by using an equalizer inspired by the inverse Hammerstein model it is possible to improve the optical reach distance in long haul coherent OFDM access networks. An invention to monitor the optical communications links and detect failures is presented in chapter V, the subject of the presented invention is an improvement of optical amplifiers used in the radio over glass systems (RoG) systems and it is applied to CATV networks. Finally, chapter VI presents general conclusions and future work.