The exponential increase of communication bandwidth demand is giving rise to the so-called 'capacity crunch' expected to materialize within the next decade. Due to the nonlinear limit of the single mode fiber predicted by the information theory, all the state-of-the-art techniques which have so far been developed and utilized in order to extend the optical fiber communication capacity are exhausted. The spatial domain of the lightwave links is proposed as a new degree of freedom that can be employed to increase the number of transmission paths and, subsequently, overcome the looming 'capacity crunch'. Therefore, the emerging technique named space-division multiplexing (SDM) is a promising candidate for creating next-generation optical networks. To realize SDM in optical fiber links, one needs to investigate novel spatially integrated devices, equipment, and subsystems. Among these elements, the SDM amplifier is a critical subsystem, in particular for the long-haul transmission system. Due to the excellent features of the erbium-doped fiber amplifier (EDFA) used in current state-of-the-art systems, the EDFA is again a prime candidate for implementing practical SDM amplifiers. However, since the SDM introduces a spatial variation of the field in the transverse plane of the optical fibers, spatially integrated erbium-doped fiber amplifiers (SIEDFA) require a careful design. In this thesis, we firstly review the recent progress in SDM, in particular, the SDM optical amplifiers. Next, we identify and discuss the key issues of SIEDFA that require scientific investigation. After that, the EDFA theory is briefly introduced and a corresponding numerical modeling that can be used for simulating the SIEDFA is proposed. Based on a home-made simulation tool, we propose a novel design of an annular based doping profile of few-mode erbium-doped fibers (FM-EDF) and numerically evaluate the performance of single stage as well as double-stage few-mode erbium-doped fiber amplifiers (FM-EDFA) based on such fibers. Afterward, we design annular-cladding erbium-doped multicore fibers (MC-EDF) and numerically evaluate the cladding pumped multicore erbium-doped fiber amplifier (MC-EDFA) based on these fibers as well. In addition to fiber design, we fabricate and characterize a multicore few-mode erbium-doped fiber (MC-FM-EDF), and perform the first demonstration of the spatially integrated optical fiber amplifiers incorporating such specialty doped fibers. Finally, we present the conclusions as well as the perspectives of this research. In general, the investigation and development of the SIEDFA will bring tremendous benefits not only for future SDM transmission systems but also for current state-of-the-art single-mode single-core transmission systems by replacing plural amplifiers by one integrated amplifier.

Long-haul optical fiber communication systems form the backbone of worldwide connectivity. In particular, submarine fiber systems today carry 99% of all data traffic between the continents, with continuing rapid growth. Increases in system reach and capacity have been enabled by new technologies as well as design approaches, among the chief examples the erbium-doped fiber amplifier (EDFA), allowing wideband optical amplification of wavelength-division-multiplexed signals, and coherent detection. Each cable uses hundreds of in-line EDFAs offering several THz of bandwidth and near-quantum-limited noise performance. The capacity of these systems is now limited by the electrical power that can be delivered to the amplifiers. Addressing this power limitation requires a new design paradigm, space-division multiplexing (SDM), which uses many parallel spatial channels, each carrying less data and less optical power, a regime in which the amplifiers are typically less efficient. Interestingly, the utility of these power-limited photonic systems is increased by operating the photonic devices less efficiently. Future growth will also rely on the ability of new paradigms employing integrated SDM approaches to scale up the number of spatial paths for lightwave communication beyond standard single-mode fibers. State-of-the-art power-limited long-haul systems have already begun to use the concept of SDM implemented as parallel single-mode fibers. On the other hand, as yet unrealized potential lies in a closer integration of communication paths or spatial channels, encompassing multicore and multimode fiber approaches, to increase the spatial information density and enable compact scaling of components. This integration is most promising in designing the amplifiers which compensate span losses periodically along a long-haul link, as higher power and cost efficiency could result from sharing power between spatial channels in multicore or multimode EDFAs. Furthermore, the strong coupling regime of multicore or multimode SDM transmission could ameliorate typical optical channel impairments due to fiber Kerr nonlinearity and mode-dependent loss or gain. In this thesis, we study the parallel single-mode SDM system paradigm before investigating strongly-coupled multimode SDM. We begin by presenting extensive measurements and modeling of power efficiency in a single-mode long-haul optical fiber transmission testbed whose design was optimized considering detailed amplifier physics. Our results demonstrate the potential for optimized power-limited SDM submarine systems to achieve Pb/s cable capacities. Next, motivated by the potential of wideband multimode and coupled-core multicore optical amplifiers, we present a unified, comprehensive treatment of the effect of polarization-dependent gain and mode-dependent gain on the capacity of strongly coupled ultra-long-haul SDM transmission systems, using simulations of a multisection model. We quantify the requirements for optical amplifiers given tolerable capacity losses, considering linear equalizers implemented in typical multiple-input multiple-output receivers. We then propose an amplifier subsystem design based on optimized multimode fiber amplifiers meeting long-haul system requirements, enabled by wavelength- and mode-selective pump couplers, towards efficient, integrated amplification for long-haul SDM systems. We also discuss challenges for multimode transmission. Finally, we shift to studying the optimization of signal design for inter-data center links that may use Kramers-Kronig receivers, which have been proposed as an intermediary between the standard direct detection and standard coherent detection paradigms of short- and long-haul optical links, respectively. By the end, we cover the full range of link lengths in long-haul optical communications, from ultra-long-haul submarine cables over ~10000 km down to campus-size links of up to ~100 km.

How is light amplified in the doped fiber? How much spontaneous emission noise is generated at the output? Do detectors with optical preamplifiers outperform avalanche photodiodes? What are the current types and architectures of amplifier-based systems? These are just a handful of the essential questions answered in Erbium-Doped Fiber Amplifiers: Principles and Applications, the first book to integrate the most influential current papers on this breakthrough in fiber-optics technology. Written by one of the pioneers in the field, this unique reference has become an essential reference for telecommunication professionals. This new paperback edition provides researchers, engineers, and system designers with detailed, interdisciplinary coverage of the theoretical underpinnings, main characteristics, and primary applications of EDFAs. Packed with information on important system experiments and the best experimental results to date as well as over 1,400 references to the expanding literature. Book jacket.

Enabling Technologies for High Spectral-efficiency Coherent Optical Communication Networks Presents the technological advancements that enable high spectral-efficiency and high-capacity fiber-optic communication systems and networks This book examines key technology advances in high spectral-efficiency fiber-optic communication systems and networks, enabled by the use of coherent detection and digital signal processing (DSP). The first of this book’s 16 chapters is a detailed introduction. Chapter 2 reviews the modulation formats, while Chapter 3 focuses on detection and error correction technologies for coherent optical communication systems. Chapters 4 and 5 are devoted to Nyquist-WDM and orthogonal frequency-division multiplexing (OFDM). In chapter 6, polarization and nonlinear impairments in coherent optical communication systems are discussed. The fiber nonlinear effects in a non-dispersion-managed system are covered in chapter 7. Chapter 8 describes linear impairment equalization and Chapter 9 discusses various nonlinear mitigation techniques. Signal synchronization is covered in Chapters 10 and 11. Chapter 12 describes the main constraints put on the DSP algorithms by the hardware structure. Chapter 13 addresses the fundamental concepts and recent progress of photonic integration. Optical performance monitoring and elastic optical network technology are the subjects of Chapters 14 and 15. Finally, Chapter 16 discusses spatial-division multiplexing and MIMO processing technology, a potential solution to solve the capacity limit of single-mode fibers. Contains basic theories and up-to-date technology advancements in each chapter Describes how capacity-approaching coding schemes based on low-density parity check (LDPC) and spatially coupled LDPC codes can be constructed by combining iterative demodulation and decoding Demonstrates that fiber nonlinearities can be accurately described by some analytical models, such as GN-EGN model Presents impairment equalization and mitigation techniques Enabling Technologies for High Spectral-efficiency Coherent Optical Communication Networks is a reference for researchers, engineers, and graduate students.

Erbium-doped fiber amplifiers are an important technology for lightwave voice, video, and data transmission. The first volume of Erbium-Doped Fiber Amplifiers: Principles and Applications offered an important exploration of the then-infant technology of erbium-doped fiber amplifiers. The passage of the 1996 Telecommunications Act and the growth of the Internet have sparked intense demand for expanded bandwidth in all network layers, resulting in significant advances in EFDA technology. Erbium-Doped Fiber Amplifiers: Device and System Developments brings telecommunications professionals up to date. Combining the contributions from four international experts in EDFAs, this new volume expands the reader's conceptual understanding of EDFAs and covers the developmental issues of EDFAs that are relevant to modern telecom applications. The authors review: New aspects in EDFA modeling, including the standard confined-doping, the transcendental-power-equation, and average-inversion-level models Design concepts for EDFAs in terrestrial and submarine WDM systems Transmission fiber design and dispersion-management techniques for terabit/s systems Amplified submarine-cable systems, including a brief history of submarine cable communications and the investigation of terabit/s system technologies Advanced concepts in the physics of noise in amplified light, noise figure definitions, entropy and ultimate capacity limits Delving into fundamental concepts (including a wealth of previously unpublished materials) as well as important breakthroughs, this much-needed resource will place telecom engineers in a position to take advantage of every aspect in the broad potential of EDFAs. "The book is an indispensable reference for researchers, development engineers, and system designers in fiber-optic communications. . . . It will excel as an introductory text in upper-level undergraduate and graduate courses on system applications of fiber optics." --Optik "One of the most comprehensive and detailed accounts of the physics and fundamental principles of erbium-doped fiber amplifiers. . . . I do not hesitate to recommend the book enthusiastically to anyone having an interest in EDFAs and their applications." --Physics Today