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1.
从理论上分析了激光器相位偏移对相干光正交频分复用(CO-OFDM)系统传输性能影响,并指出相位噪声是相干光OFDM主要噪声源。在传统无线OFDM信道估计基础上,提出了一种基于导频子载波的相位噪声估计和补偿方法,在OptiSystem中建立CO-OFDM系统仿真模型,通过仿真证明了该方法可以有效地改善CO-OFDM系统传输性能。 相似文献
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We present a channel model for a coherent optical orthogonal frequency-division-multiplexed (CO-OFDM) system including linear fiber dispersion effects and noises from optical amplifiers and intercarrier interference induced by laser phase noise. Based upon this model, we derive maximum-likelihood (ML) phase estimation and channel estimation for the CO-OFDM system. Both computer simulation and transmission experiment of the CO-OFDM system show that the ML decision-feedback following pilot-assisted phase estimation gives the optimal performance. 相似文献
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《Lightwave Technology, Journal of》2010,28(4):494-501
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In this paper, a novel data-aided linear fitting-based (DALF-based) blind phase estimation method for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) is proposed. Similar to our previous work done in the pilot-based blind phase estimation method, the pilot subcarriers are used to transmit unknown amplitude modulation signals in order to improve spectral efficiency. But the so-called pilot subcarriers can be reduced to only two in the DALF-based method, while the conventional pilot-aided-based (PA-based) method requires almost four real pilot subcarriers. A performance comparison of the conventional PA-based and DALF-based phase estimation methods has been demonstrated through a 16-QAM CO-OFDM simulation. The results show that the performance of the proposed DALF-based method is better than the conventional one with higher SE and has the potential in the large capacity CO-OFDM systems. 相似文献
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提出了一种采用基于光学相位分集接收技术实现远程相干光正交频分复用(CO-OFDM)信号的远程光接入方案,并进行了理论研究和仿真验证。在本方案中,没有使用色散补偿光纤(DCF)或者色散补偿模块(DCM)补偿光纤信道色散导致的负面效应,原因是CO-OFDM信号能有效抵抗传输过程中色度色散(CD)和偏振模色散(PMD)引起的负面效应。仿真结果表明,10Gbit/s CO-OOFDM信号在标准单模光纤(SMF-28)传输320km后,采用相位估计技术得到的OFDM电信号,其时域波形的相位抖动幅度更小;与采用光载波自提取技术接收相位调制COOFDM的方案进行比较,测试误差向量幅度(EVM)的结果表明,本文方案可以获得更好的COOFDM信号接收性能,星座图中星座点收敛更加紧凑,接收的CO-OFDM信号质量更高。 相似文献
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Xingwen Yi William Shieh Yiran Ma 《Lightwave Technology, Journal of》2008,26(10):1309-1316
There are three major advantages for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) transmission using digital signal processing. First, coherent detection is realized by digital phase estimation without the need for optical phase-locked loop. Second, OFDM modulation and demodulation are realized by the well-established computation-efficient fast Fourier transform (FFT) and inverse FFT. Third, adaptive data rates can be supported as different quadrature amplitude modulation (QAM) constellations are software-defined, without any hardware change in transmitter and receiver. However, it is well-known that coherent detection, OFDM, and QAM are all susceptible to phase noise. In this paper, theoretical, numerical, and experimental investigations are carried out for phase noise effects on high spectral efficiency CO-OFDM transmission. A transmission model in the presence of phase noise is presented. By using simulation, the bit error rate floors from finite laser linewidth are presented for CO-OFDM systems with high-order QAM constellations. In the experiments, the phase noise effects from both laser linewidth and nonlinear fiber transmission are investigated. The fiber nonlinearity mitigation based on receiver digital signal processing is also discussed. 相似文献
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Coherent Optical 25.8-Gb/s OFDM Transmission Over 4160-km SSMF 总被引:1,自引:0,他引:1
Jansen S.L. Morita I. Schenk T.C.W. Takeda N. Tanaka H. 《Lightwave Technology, Journal of》2008,26(1):6-15
We discuss coherent optical orthogonal frequency division multiplexing (CO-OFDM) as a suitable modulation technique for long-haul transmission systems. Several design and implementation aspects of a CO-OFDM system are reviewed, but we especially focus on phase noise compensation. As conventional CO-OFDM transmission systems are very sensitive to laser phase noise a novel method to compensate for phase noise is introduced. With the help of this phase noise compensation method we show continuously detectable OFDM transmission at 25.8 Gb/s data rate (20 Gb/s after coding) over 4160-km SSMF without dispersion compensation. 相似文献
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Coherent optical orthogonal frequency division multiplexing (CO-OFDM) is considered as a key solution for long haul optical fiber communication systems thanks to its high spectral efficiency and robustness against chromatic dispersion. We have investigated a CO-OFDM based on quadrature phase shift keying (QPSK)-OFDM and 16 quadrature amplitude modulation (16QAM)-OFDM over 500 km uncompensated fiber links. The simulation results show that the proposed system is a promising solution to meet the aggregate data rate demands cost effectively in future high-speed optical communication systems. 相似文献
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In this paper, a simple and robust pilot-aided carrier phase estimation scheme with a modified phase unwrapping is proposed. The principle of the proposed phase unwrapping is shown with a step-by-step procedure. Further, we test the post-FEC BER performance for the pilot-aided carrier phase estimation scheme with the traditional and proposed phase unwrapping. For the proposed phase unwrapping, a cycle slip rate reduction of about 10 times is achieved than the case using the traditional phase unwrapping through simulations in the presence of Wiener phase noise. Finally, we present a 2.2 Eb/N0 gain and post-FEC error-free performance with only 0.78 % pilot overhead in a 32-Gbaud QPSK system using soft-decision forward error correction. 相似文献
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An efficient channel estimation method called time-domain weighted average (TWA) algorithm is proposed for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. On the premise of calculating the associated weight of channel transfer function, a more exact channel characteristic is obtained by calculating the weighted average of the pilot transfer function in this algorithm. Compared with time-domain average (TA) algorithm, the TWA algorithm can reach the same bit error rate (BER) with fewer pilots, and it improves the performance of CO-OFDM systems. 相似文献
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Orthogonal frequency division multiplexing (OFDM) is a suitable solution thanks to its many advantages known in wireless communications. On the other hand, optical communications is also used as a backbone to transmit and receive large data rates with economical and good performance. Recently, fiber optical communication and OFDM method have been combined to obtain both advantages in a communication link called Coherent Optical OFDM (CO-OFDM). In this study, Bit error rate (BER) versus distance variations are investigated for a constant signal to noise ratio in CO-OFDM systems. Results also show the performance of the CO-OFDM system at different data rates and distances for one RF carrier and one optical carrier. So far, the Telecommunication Standardization Sector standards have suggested 81 channels between 192.1 and 196.1 THz in C band. Extending the number of channels using 111 more channels between 185.9 and 191.4 THz in L band where optical amplifiers and laser sources are available, the total number of channels reaches up to 192. In this research, CO-OFDM technique is modeled and simulated designing a Monte Carlo simulation. Dense wavelength division multiplexing (DWDM) is the key factor to obtain 3 Tb/s (192*16 Gb/s) utilizing only one optical cable by covering whole C and L bands. To the best of our knowledge, this work shows the first BER versus Distance variations in a CO-OFDM communication link for 3 Tb/s. 相似文献
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由于相干光正交频分复用(CO-OFDM)系统具有很高的峰均功率比(PAPR)以及非常近的子载波间隔,使得光纤非线性损伤成为系统的决定因素。提出中间位置光学相位共轭(OPC)补偿算法补偿CO-OFDM的Kerr损伤,由于OPC两端链路对称,可以最大限度地保证满足补偿条件,具有很好的非线性补偿效果。而且无链路色散补偿和有链路色散补偿系统均适用。该算法能使单信道40 Gb/s CO-OFDM的最大Q因子提高3 dB,非线性阈值提高4 dB;波分复用(WDM)系统的最大Q因子能提高1.1 dB,非线性阈值提高1 dB。 相似文献
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We present an extra processing added to conventional least square (LS) channel estimation to further improve its per- formance in coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. The influence of noise, chromatic dispersion and polarization mode dispersion on the performance of the proposed algorithm is analyzed. The simulation results show that the improved algorithm has better performance and lower complexity. 相似文献
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相干光正交频分复用系统(Coherent Optical Orthogonal Frequency Division Multiplexing, CO-OFDM)作为未来高速光通信的重要解决方案,是近年来光传输领域的研究热点。高速CO-OFDM系统需要较高带宽的模数/数模转换器(DAC/ADC),目前技术水平难以达到。文章改进了正交频带复用技术(Orthogonal Band Multiplexing , OBM)的光域实现方案;结合偏振复用技术和偏振分集接收,提出了基于OBM的100Gb/s高速CO-OFDM系统;并对系统传输性能进行数字仿真。结果表明:基于OBM技术的MIMO CO-OFDM系统可有效降低对DAC/ADC的处理速度要求,在不需任何在线色散补偿和偏振控制器件条件下,通过单模光纤传输800km,系统Q值保持在13dB以上。 相似文献
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In single frequency network (SFN), there exist some special long delay spread channels as well as conventional multipath channels.
For pilot-aided orthogonal frequency division multiplex (OFDM) systems, channel estimation is usually accomplished by interpolation
with pilots. However, few pilot sub-carriers exist within the coherent bandwidth of the long delay spread channels in SFN.
In this case, conventional frequency domain interpolation methods cannot work properly. In a narrowband channel, this paper
indicates that both the real and the imaginary parts of channel frequency response can be accurately approximated as a sine-wave
with DC offset. For many practical pilot-aided OFDM systems, the bandwidth of the narrowband channel mentioned before is comparable
with the interval between several adjacent pilot sub-carriers. Then this paper proposes a sine-wave based frequency domain
interpolation method for the channel estimation of pilot-aided OFDM systems in SFN. As simulation results show, the proposed
method performs well in the long delay spread channel, whereas the mismatched Wiener interpolation filter (WIF) estimates
channel response inaccurately. Moreover, the proposed method gives accurate channel estimation in conventional multipath channels,
especially for the systems which adopt high order modulations. 相似文献
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《Optical Fiber Technology》2014,20(3):268-273
To improve the outage performance of an optical orthogonal frequency-division multiplexing (OFDM) system under the frequency offset between the sampling clocks in the transmitter and receiver, a pilot-aided sampling frequency offset (SFO) estimation and compensation scheme for the optical OFDM system with intensity-modulation and direct-detection (DD-OOFDM) is experimentally demonstrated. The experimental and simulated results show that the scheme can work effectively even with large sampling frequency offsets. In addition, it can achieve a good bit error rate (BER) performance without the sampling clock frequency synchronization in the receiver. 相似文献
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《Lightwave Technology, Journal of》2009,27(16):3511-3517