Theoretical and Experimental Study on High Spectral Efficiency Coherent Optical OFDM Systems PDF Download

Author: Chen Xi
Publisher:
ISBN:
Category : Fiber optics
Languages : en
Pages : 206

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Author: Hussin Saleh Ibrahim Saied Saleh
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
Orthogonal frequency division multiplexing (OFDM) belongs to multicarrier technology which is used in many broadband wired and wireless communication systems. It is used to combat multipath fading. Although, OFDM systems are complex compared to single carrier systems due to design of their transmitter and receiver and also the associated signal processing, significant benefits are achieved. Optical OFDM systems can be classified into three approaches according to the detection scheme. The approaches are direct detection optical OFDM (DDO-OFDM), coherent optical OFDM (CO-OFDM) and self coherent optical OFDM (SCO-OFDM). The most important drawbacks of CO-OFDM are the high peak-to-average power ratio (PAPR), high sensitivity to frequency offset and phase noise. The present dissertation introduces the performance of different pulse shaping techniques. Furthermore, it presents new algorithms to reduce the phase noise effects and compares the system performance with different existing algorithms. Moreover, the performance of a new system design is investigated. The provided dissertation includes four original contributions.Initially, the theoretical principles of OFDM are presented with detailing on the advantages and disadvantages of OFDM compared to the single carrier modulation technology. The theoretical fundamentals of optical OFDM and the differences between the three systems are followed. Furthermore, performance of the three existing optical OFDM systems are elaborated and compared. A square root raised-cosine pulse shaping of OFDM symbols is suggested to enhance the efficiency of CO-OFDM systems. Next, the different kinds of the phase noise effects on the OFDM signals are defined and the impact of the laser and nonlinear phase noise is reported. Different existing phase noise compensation algorithms are presented. Moreover, the modified and new phase noise compensation schemes are provided and compared. ; eng

Author: Xiang Zhou
Publisher: John Wiley & Sons
ISBN: 1118714962
Category : Science
Languages : en
Pages : 649

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Book Description
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.

Author: Omar Jan
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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In this dissertation, a simulation study of coherent-optical OFDM (CO-OFDM) systems has been conducted. Fiber nonlinearities are the main limitation for long-haul CO-OFDM transmission. A second limitation is the high impact of laser phase noise (LPN) imposed by the large linewidth of low-cost distributed feedback (DFB) lasers. Furthermore, high-order constellations (16-QAM) combined with large OFDM symbols (1024-point inverse fast Fourier transform (IFFT)/fast Fourier transform (FFT)) increase the penalty of such impairments. The larger OFDM symbols reduce the overhead of the cyclic prefix, and high-order constellations provide high spectral efficiency. Therefore, several combination techniques have been proposed and studied to alleviate the effect of fiber nonlinearities for long-haul CO-OFDM systems and of LPN for CO-OFDM systems that use DFB lasers. The experimental demonstration of CO-OFDM systems has been achieved in this dissertation using off-line processing, where the received data are stored by a sampling oscilloscope and then evaluated using MATLAB. First, the experimental setups of a homodyne CO-OFDM system and a self-homodyne CO-OFDM system have been carried out with DFB lasers. Two-stage LPN mitigation is then proposed, for which the experimental results exhibit an improvement in the bit error ratio (BER). Second, some experiments have been carried out to investigate the impact of LPN on DFT-spread CO-OFDM systems. Furthermore, a new spectral shaping technique for DFT-spread OFDM has been experimentally studied over a distance of approximately 347 km. ; eng

Author: Masataka Nakazawa
Publisher: Springer Science & Business Media
ISBN: 3642104193
Category : Science
Languages : en
Pages : 337

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Book Description
The growth of Internet traf?c in recent years surpassed the prediction of one decade ago. Data stream in individual countries already reached terabit/s level. To cope with the petabit class demands of traf?c in coming years the communication engineers are required to go beyond the incremental improvement of today’s technology. A most promising breakthrough would be the introduction of modulation f- mats enabling higher spectral ef?ciency than that of binary on–off keying scheme, virtually the global standard of ?ber-optic communication systems. In wireless communication systems, techniques of high spectral density modulation have been well developed, but the required techniques in optical frequency domain are much more complicated because of the heavier ?uctuation levels. Therefore the past trials of coherent optical modulation/detection schemes were not successful. However, the addition of high-speed digital signal processing technology is the fundam- tal difference between now and two decades ago, when trials of optical coherent communication systems were investigated very seriously. This approach of digital coherent technology has attracted keen interest among communication specialists, as indicated by the rapid increase in the pioneering presentations at the post-deadline sessions of major international conferences. For example, 32 terabit/s transmission in a ?ber experiment based on this technology was reported in post-deadline session of Optical Fiber Communication Conference (OFC) 2009. The advancement of the digital coherent technologies will inevitably affect the network architecture in terms of the network resource management for the new generation photonic networks, rather than will simply provide with huge transmission capacity.

Author: Daniel Jose Fernandes Barros
Publisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 160

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Book Description
The drive towards higher spectral efficiency and maximum power efficiency in optical systems has generated renewed interest in the optimization of optical transceivers. In this work, we study the different optical applications: Wide Area Networks (WANs), Metropolitan Area Networks (MANs), Local Area Networks (LANs) and Personal Area Networks (PANs). In WANs or long-haul systems, orthogonal frequency-division multiplexing (OFDM) can compensate for linear distortions, such as group-velocity dispersion (GVD) and polarization-mode dispersion (PMD), provided the cyclic prefix is sufficiently long. Typically, GVD is dominant, as it requires a longer cyclic prefix. Assuming coherent detection, we show how to analytically compute the minimum number of subcarriers and cyclic prefix length required to achieve a specified power penalty, trading off power penalties from the cyclic prefix and from residual inter-symbol interference (ISI) and inter-carrier interference (ICI). We derive an analytical expression for the power penalty from residual ISI and ICI. We also show that when nonlinear effects are present in the fiber, single-carrier with digital equalization outperforms OFDM for various dispersion maps. We also study the impairments of electrical to optical conversion when using Mach-Zehnder (MZ) modulators. OFDM has a high peak-to-average ratio (PAR), which can result in low optical power efficiency when modulated through a Mach-Zehnder (MZ) modulator. In addition, the nonlinear characteristic of the MZ can cause significant distortion on the OFDM signal, leading to in-band intermodulation products between subcarriers. We show that a quadrature MZ with digital pre-distortion and hard clipping is able to overcome the previous impairments. We consider quantization noise and compute the minimum number of bits required in the digital-to-analog converter (D/A). Finally, we discuss a dual-drive MZ as a simpler alternative for the OFDM modulator, but our results show that it requires a higher oversampling ratio to achieve the same performance as the quadrature MZ. In MANs, we discuss the use OFDM for combating GVD effects in amplified direct-detection (DD) systems using single-mode fiber. We review known direct-detection OFDM techniques, including asymmetrically clipped optical OFDM (ACO-OFDM), DC-clipped OFDM (DC-OFDM) and single-sideband OFDM (SSB-OFDM), and derive a linearized channel model for each technique. We present an iterative procedure to achieve optimum power allocation for each OFDM technique, since there is no closed-form solution for amplified DD systems. For each technique, we minimize the optical power required to transmit at a given bit rate and normalized GVD by iteratively adjusting the bias and optimizing the power allocation among the subcarriers. We verify that SSB-OFDM has the best optical power efficiency among the different OFDM techniques. We compare these OFDM techniques to on-off keying (OOK) with maximum-likelihood sequence detection (MLSD) and show that SSB-OFDM can achieve the same optical power efficiency as OOK with MLSD, but at the cost of requiring twice the electrical bandwidth and also a complex quadrature modulator. We compare the computational complexity of the different techniques and show that SSB-OFDM requires fewer operations per bit than OOK with MLSD. In LANs, we compare the performance of several OFDM schemes to that of OOK in combating modal dispersion in multimode fiber links. We review known OFDM techniques using intensity modulation with direct detection (IM/DD), including DC-OFDM, ACO-OFDM and pulse-amplitude modulated discrete multitone (PAM-DMT). We describe an iterative procedure to achieve optimal power allocation for DC-OFDM, and compare analytically the performance of ACO-OFDM and PAM-DMT. We also consider unipolar M-ary pulse-amplitude modulation (M-PAM) with minimum mean-square error decision-feedback equalization (MMSE-DFE). For each technique, we quantify the optical power required to transmit at a given bit rate in a variety of multimode fibers. For a given symbol rate, we find that unipolar M-PAM with MMSE-DFE has a better power performance than all OFDM formats. Furthermore, we observe that the difference in performance between M-PAM and OFDM increases as the spectral efficiency increases. We also find that at a spectral efficiency of 1 bit/symbol, OOK performs better than ACO-OFDM using a symbol rate twice that of OOK. At higher spectral efficiencies, M-PAM performs only slightly better than ACO-OFDM using twice the symbol rate, but requires less electrical bandwidth and can employ analog-to-digital converters at a speed only 81% of that required for ACO-OFDM. In PANs, we evaluate the performance of the three IM/DD OFDM schemes in combating multipath distortion in indoor optical wireless links, comparing them to unipolar M-PAM with MMSE-DFE. For each modulation method, we quantify the received electrical SNR required at a given bit rate on a given channel, considering an ensemble of 170 indoor wireless channels. When using the same symbol rate for all modulation methods, M-PAM with MMSE-DFE has better performance than any OFDM format over a range of spectral efficiencies, with the advantage of M-PAM increasing at high spectral efficiency. ACO-OFDM and PAM-DMT have practically identical performance at any spectral efficiency. They are the best OFDM formats at low spectral efficiency, whereas DC-OFDM is best at high spectral efficiency. When ACO-OFDM or PAM-DMT are allowed to use twice the symbol rate of M-PAM, these OFDM formats have better performance than M-PAM. When channel state information is unavailable at the transmitter, however, M-PAM significantly outperforms all OFDM formats. When using the same symbol rate for all modulation methods, M-PAM requires approximately three times more computational complexity per processor than all OFDM formats and 63% faster analog-to-digital converters, assuming oversampling ratios of 1.23 and 2 for ACO-OFDM and M-PAM, respectively. When OFDM uses twice the symbol rate of M-PAM, OFDM requires 23% faster analog-to-digital converters than M-PAM but OFDM requires approximately 40% less computational complexity than M-PAM per processor.

Author: Zuraidah Zan
Publisher:
ISBN:
Category : Lasers
Languages : en
Pages : 588

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Book Description
In recent years, researchers and network equipment manufacturers have focused on the development of a 100 Gb/s optical transmission systems to cater the ever increasing demands for bandwidth. To cater the demands, optical orthogonal frequency division multiplexing (O-OFDM) has been proposed. O-OFDM has been shown as a promising technique to increase spectral efficiency with its ability to compensate for chromatic and polarisation mode dispersion. There are two forms of receiver used for long haul O-OFDM links: coherent-OOFDM (CO-OFDM) and direct detection O-OFDM (DDO-OFDM). The CO-OFDM system is known to be limited by the laser's phase noise, where the system requires a narrow linewidth laser at both transmitter and receiver, where these lasers phase must track one-another. In the DDO-OFDM system, an optical carrier is transmitted along with the subcarriers so both originate from the same laser, and both experience the same degradations along the fibre. Thus, the linewidth, or equivalently phase-noise, requirements are far less stringent than for CO-OFDM systems. However, given that laser phase noise will be converted to intensity noise (PM-to-IM conversion noise) along a dispersive fibre, there will be some effect on performance in a DDO-OFDM system. The question is whether this is significant, given that the fibre dispersion is not optically compensated as in conventional lightwave systems.In this thesis, laser phase noise effect upon detection in a DDO-OFDM system is shown to impose broad noise pedestal around a subcarrier for higher frequency subcarriers when there is a high accumulated dispersion. The noise pedestal can introduce inter-subcarrier-interference between the adjacent subcarriers. This is different in a CO-OFDM system, where the phase noise is independent of the subcarriers' frequency and common to all subcarriers. This thesis focuses on the DDO-OFDM system using external modulation at the transmitter. A transmission system was developed to study the effects of the laser relative intensity noise (RIN) and phase noise over a long-haul transmission, and to show the importance of the laser's characteristics. Experimental measurements on a commercial fixed-wavelength distributed feedback (DFB) laser investigated its RIN, linewidth and light vs. current (L-I) characteristics. The effect of external modulation of this laser was investigated. With the externally-modulated transmitter, the laser chirp is ignored. The linewidth measurement was done using self-homodyne technique and validated using a high-resolution spectrophotometer. The measurements showed inter-dependency between the linewidth and RIN, which agreed with theory. A laser linewidth emulator was developed and demonstrated experimentally. This was done by phase modulating a semiconductor's laser output to broaden its linewidth. With this laser, the linewidth can be made independent from the other laser's noise characteristics. Simulations and experiments were performed to study the interaction of linewidth and fibre dispersion. The interaction produces noise conversion from phase modulation to intensity modulation, where the noise PSD was obtained. An analytical equation of the PM-to-IM's upper-bound was derived and plotted on the noise PSD's amplitude. When the laser was modulated with RF tones, a noise pedestal around each of the tones was obtained. The peak power of the noise is shown to increase with the increased of the tone's frequency. This is due to the phase walk-off of the high frequency subcarrier from the carrier is larger than the low frequency subcarrier. The peak also increases when a wider linewidth was used. This noise was shown to cause phase rotations of the received symbols and reduces the Q performance of the DDO-OFDM system. To reduce the effect of the linewidth in the DDO-OFDM system, an experiment using a simple delay line to match the delay experienced by the subcarrier was performed. The result shows improvement of the subcarriers' Q performance. Finally, this thesis also presented the performance of the DDO-OFDM system in transmitting high-speed data of 120 Gbit/s. This experiment involved several important device improvements in order to achieve a good quality and wide RF-signal bandwidth. In this transmission, a variant of the DDO-OFDM system employing self-coherent polarization-diversity receiver design was developed.

Author: Biswanath Mukherjee
Publisher: Springer Nature
ISBN: 3030162508
Category : Technology & Engineering
Languages : en
Pages : 1169

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Book Description
This handbook is an authoritative, comprehensive reference on optical networks, the backbone of today’s communication and information society. The book reviews the many underlying technologies that enable the global optical communications infrastructure, but also explains current research trends targeted towards continued capacity scaling and enhanced networking flexibility in support of an unabated traffic growth fueled by ever-emerging new applications. The book is divided into four parts: Optical Subsystems for Transmission and Switching, Core Networks, Datacenter and Super-Computer Networking, and Optical Access and Wireless Networks. Each chapter is written by world-renown experts that represent academia, industry, and international government and regulatory agencies. Every chapter provides a complete picture of its field, from entry-level information to a snapshot of the respective state-of-the-art technologies to emerging research trends, providing something useful for the novice who wants to get familiar with the field to the expert who wants to get a concise view of future trends.

Author: Narottam Das
Publisher: BoD – Books on Demand
ISBN: 9535117300
Category : Technology & Engineering
Languages : en
Pages : 228

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Book Description
High-speed optical communication is very much useful in telecommunication systems, data processing and networking. It consists of a transmitter that encodes a message into an optical signal, a channel that carries this optical signal to its desired destination, and a receiver that reproduces the message from the received optical signal. It presents up to date results on communication systems, along with the explanations of their relevance, from leading researchers in this field. The chapters of this book cover general concepts of high-speed optical communication, optical devices used optical communication, and optical communication systems. In recent years, optical devices and other enhanced signal processing functions are also considered in depth for high-speed optical communications systems. Commonly used optical devices are light emitting diodes and photodetectors. This book is targeted at research, development and design engineers from the teams in manufacturing industry, academia and telecommunication industries.

Author: Chang, Frank
Publisher: River Publishers
ISBN: 8793609221
Category : Computers
Languages : en
Pages : 760

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Book Description
In recent years, investments by cloud companies in mega data centers and associated network infrastructure has created a very active and dynamic segment in the optical components and modules market. Optical interconnect technologies at high speed play a critical role for the growth of mega data centers, which flood the networks with unprecedented amount of data traffic. Datacenter Connectivity Technologies: Principles and Practice provides a comprehensive and in-depth look at the development of various optical connectivity technologies which are making an impact on the building of data centers. The technologies span from short range connectivity, as low as 100 meters with multi-mode fiber (MMF) links inside data centers, to long distances of hundreds of kilometers with single-mode fiber (SMF) links between data centers. This book is the first of its kind to address various advanced technologies connecting data centers. It represents a collection of achievements and the latest developments from well-known industry experts and academic researchers active in this field. Technical topics covered in this book include: Mega data center requirementsHigh volume VCSELsDirectly modulated lasersElectro-absorption modulated lasersPulse amplitude modulation (PAM)Discrete Multi-Tone modulation (DMT)Optical Duobinary TransmissionOptical fibers and connectorsMach-zenhder modulatorsSilicon photonicsOptical waveguide devices and packagingTesting and measurementsAdvanced modulation formatsOptical coherent networksHigh-speed IC design & packaging