Impairment analysis and mitigation for cost-effective OFDM-based access systems

• Main Author: Duarte Sequeira André, Nuno Miguel
• Other Authors: Petermann, Klaus, Technische Universität Berlin, Hanik, Norbert, Jungnickel, Volker
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2020
• Subjects: 620 Ingenieurwissenschaften; fibre optics communications; OFDM; access systems; direct modulation; direct detection; Glasfaserkommunikation; orthogonales Frequenzmultiplexverfahren; Zugangssysteme; Direktmodulation; Direktdetektion; DML
• Online Access: https://depositonce.tu-berlin.de/handle/11303/10528; https://doi.org/10.14279/depositonce-9459

The growth in broadband connection speed has been exponential, and this trend will continue in the foreseeable future [1]. An access network is a connection between users and service providers and therefore a key element in support of this growth. While expanding its broadband offer a service provider must ensure seamless migration through compatibility with legacy networks, and also create an offer that is attractive to customers. Access networks are designed to support numerous users at different distances from the service provider. Cost-efficiency is mandatory. It usually relies upon using Passive Optical Networks (PONs) and low complexity electro-optical devices (direct modulation/detection), whose performance can be unlocked by digital signal processing to mitigate components’ limitations. Novel optical modulation formats help to achieve large spectral efficiencies and allow advanced signal distribution. One such modulation format is Orthogonal Frequency Division Multiplexing (OFDM), which offers a compact spectrum, resilience to chromatic dispersion and flexible subcarrier allocation [2]. Legacy PON systems use C-band (1500nm) downlinks and O-band (1330nm) uplinks [3]–[9]. The C-band has low attenuation at the cost of higher chromatic dispersion [10]. The O-band has practically no chromatic dispersion but higher attenuation [10] enabling the use of simpler transmitters, Directly Modulated Lasers (DMLs) for example. The latest PON systems must enable parallel operation with legacy systems. For this reason they operate both in the C-band down- and uplink [11]. A DML has chirp as a by-product of transmission [12], [13]. Chirp interacts with fibre chromatic dispersion (C-band) to create Subcarrier-to-Subcarrier Intermixing Interference (SSII) at the receiver after direct detection [14]. This occurs despite OFDM’s resilience to chromatic dispersion and is one of the main impairments of cost-effective OFDM-based access systems. The main contribution of this work is to predict and analyse the impact of SSII as an ...