Advanced Digital Signal Processing for Next-generation Coherent Optical Communication Systems
Author | : Meng Qiu |
Publisher | : |
Total Pages | : |
Release | : 2017 |
ISBN-10 | : OCLC:1000103182 |
ISBN-13 | : |
Rating | : 4/5 (82 Downloads) |
Book excerpt: "Coherent detection combined with digital signal processing (DSP) has been widely adopted in modern fiber-optic transport for long-haul and medium reach applications. Compared with direct detection systems, coherent communication systems can significantly improve the receiver sensitivity and increase the transmission capacity. The ever-increasing demand for greater transport network capacity necessitates continuous upgrade of future fiber transmission systems. In such context, novel advanced DSP schemes are necessary to satisfy the requirements of next-generation coherent optical communication systems.In this thesis, we present several advanced DSP techniques to cope with both linear and nonlinear impairments in coherent optical communication systems with data rates of 100 Gb/s and beyond. First, two effective low-complexity algorithms for carrier recovery in single carrier coherent systems are presented. Specifically, we describe a frequency offset (FO) tracking algorithm that can dynamically compensate the FO in intradyne coherent systems to avoid potential performance degradation caused by stochastic frequency drift of lasers. In addition, we demonstrate a format-transparent carrier phase recovery (CPR) algorithm based on interleaved superscalar parallelization, which can be economically implemented in practice because it can minimize the required pilot symbol overhead and buffer size in the superscalar parallelization structure. Second, we explore the digital subcarrier multiplexing (SCM) technique and discuss its benefits. Specifically, we employ SCM signals in a long-haul transmission scenario to demonstrate the improved tolerance to both fiber nonlinearity and laser linewidth when the number of subcarriers is optimized. Furthermore, we explore the enhanced flexibility of the DSP design in SCM systems and propose a novel joint CPR algorithm for the correction of cycle slips (CS). Finally, we conduct studies on a low-cost solution for medium reach transmission, namely the Stokes-vector direct detection (SV-DD) systems. We demonstrate that the laser linewidth tolerance of SV-DD systems is limited by equalization-enhanced phase noise (EEPN) and verify that the EEPN induced performance degradation can be mitigated by a simple maximum likelihood (ML) phase recovery stage. All the aforementioned DSP techniques have been demonstrated by simulations and experiments based on our leading-edge coherent optical transmission testbed." --