Nonlinear Effects Mitigation in Coherent Optical OFDM System in Presence of High Peak Power PDF Download

Author: Yanir London
Publisher:
ISBN:
Category : Digital control systems
Languages : en
Pages : 132

View

Book Description

Author: Rakefet Weidenfeld-Levi
Publisher:
ISBN:
Category :
Languages : en
Pages : 159

View

Book Description

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

View

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: Iraj Sadegh Amiri
Publisher:
ISBN: 9781536131451
Category : Optical communications
Languages : en
Pages : 0

View

Book Description
Due to the limitation of the electrical OFDM signal and electrical Fast Fourier Transform (FFT), all-optical OFDMs have recently received much attention. Accordingly, this research study was conducted to investigate the effect of phase noise in the performance of an all-optical OFDM transmission system with 4-point FFT single mode fiber (SMF) links by considering the effects of fiber length, input laser power and a number of channels. In all optical systems, the transmitter side consists of a comb power generator, wavelength selected switch and an optical QAM generator. A comb power generator generates channels with a frequency separation of ∆f=25 GHz. Subsequently, a Wavelength Selected Switch (WSS) was used to split subcarriers and then the subcarriers were modulated individually with Optical QAM modulators. As the results show, a higher number of channels led more phase noise in terms of XPM and FWM nonlinearities, and signal power was the main factor in nonlinear fiber optics. As a consequence, there is more phase noise distortion at a higher signal power for a higher number of channels rather than the lower number of channels.

Author: Mustafa Alaulddin Bahaulddin Al-Qadi
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659393617
Category :
Languages : en
Pages : 96

View

Book Description
This work addresses theoretically some issues related to CO-OFDM system and identifies some parameters that affect its performance. The performance of a long-haul CO-OFDM system is simulated taking into account the effect of fiber chromatic dispersion, polarization mode dispersion, and nonlinear fiber optic effects. A theoretical study regarding the relation between the number of subcarriers and the mean launched optical power is carried out and supported by simulation results. The study reveals that there is an optimum launched power value for a fixed number of subcarriers. Further, The inphase/quadrature (I/Q) amplitude and phase imbalance effects are studied in CO-OFDM and an analytical model for the I/Q imbalance is developed and supported by simulation results. The results indicate that the I/Q imbalance degrades the BER performance considerably.Simulation results are obtained using OptiSystem (version 9.0) software package.

Author: Jie Pan
Publisher:
ISBN:
Category : Fiber optics
Languages : en
Pages : 78

View

Book Description
One major drawback of a Coherent-Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) system is its sensitivity to fiber nonlinearity. It has been shown that a Volterra series based nonlinear equalizer can compensate distortion introduced by the fiber nonlinearity. One major disadvantage of Volterra series is its complexity which can be reduced by removing its "unimportant" coefficients. The resulting Volterra system is called the sparse Volterra system. The Wiener-Hammerstein model is another popular nonlinear signal processing technique with a simpler structure. In this thesis, the nonlinear distortion of a CO-OFDM system is investigated, and equalizers based on Volterra model, sparse Volterra model and Wiener-Hammerstein model are designed. This is the first attempt to apply the Wiener-Hammerstein model to compensate nonlinear distortion in optical communication systems. A comparison between predistorters and equalizers is also presented. To the best of author's knowledge, no such a study has ever been conducted for optical communication systems.

Author: Faisal Tariq
Publisher: LAP Lambert Academic Publishing
ISBN: 9783844323641
Category :
Languages : en
Pages : 108

View

Book Description
Orthogonal Frequency Division Multiplexing (OFDM) is a promising technique for recent and future wireless communication systems mainly due to its high spectral efficiency and inherent capacity to combat Inter Symbol Interference (ISI). However it suffers from nonlinear error problem, popularly known as high Peak to Average Power Ratio (PAPR) due to nonlinear transfer function of Power Amplifiers in Transmitters. It causes severe performance degradation to the systems that employ link adaptation for achieving better efficiency such as LTE and WiMAX. Therefore it is important to understand the nature and impact of the error. This book will discuss basics of OFDM and provide an in depth understanding of the nonlinear error and its impact of link adaptive OFDM systems. It also provides detail simulation results and analysis of its impact on the system for different channel condition, modulation and FEC coding rate. Finally a compensation technique will be introduced to overcome the impact of nonlinear errors.

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

View

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: Jinlong Wei
Publisher: MDPI
ISBN: 3039363980
Category : Technology & Engineering
Languages : en
Pages : 162

View

Book Description
Artificial intelligence is deeply involved in our daily lives via reinforcing the digital transformation of modern economies and infrastructure. It relies on powerful computing clusters, which face bottlenecks of power consumption for both data transmission and intensive computing. Meanwhile, optics (especially optical communications, which underpin today’s telecommunications) is penetrating short-reach connections down to the chip level, thus meeting with AI technology and creating numerous opportunities. This book is about the marriage of optics and AI and how each part can benefit from the other. Optics facilitates on-chip neural networks based on fast optical computing and energy-efficient interconnects and communications. On the other hand, AI enables efficient tools to address the challenges of today’s optical communication networks, which behave in an increasingly complex manner. The book collects contributions from pioneering researchers from both academy and industry to discuss the challenges and solutions in each of the respective fields.

Author: Gal Shulkind
Publisher:
ISBN:
Category :
Languages : en
Pages : 110

View

Book Description