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1.
Nonreturn-to-zero (NRZ) and return-to-zero (RZ) signal formats are experimentally and numerically compared for single-channel long-distance transmission in an in-line amplifier system with dispersion management providing average zero dispersion and local nonzero dispersion at an interval equal to the in-line amplifier spacing. Among a 20-ps RZ signal, a 40-ps RZ signal, and an NRZ signal transmitted in 10 Gb/s straight-line experiments, the last signal achieves the longest transmission distance of 6000 km while the others are limited to 4400 km. Numerical simulations explain these results well and show that, along with linear amplified spontaneous emission (ASE) accumulation, signal waveform distortion due to the combined effect of higher order group-velocity dispersion (GVD) and self-phase modulation (SPM) dominates the performance. Nonlinear optical noise enhancement is not obvious because of the fiber dispersion arrangement. Signals with large pulse widths are less affected by the combined effect, while small-width signals yield superior initial signal-to-noise ratio (SNR) as determined by optical noise. A detailed simulation indicates that a pulse width of about 60 ps is optimum for long distance transmission under the fiber dispersion arranged in this paper 相似文献
2.
Takachio N. Norimatsu S. Iwashita K. Yonenaga K. 《Lightwave Technology, Journal of》1994,12(2):247-253
Even if the amplitude of a phase-modulated optical signal is constant before transmission, amplitude modulation is caused by fiber chromatic dispersion. As a result, self-phase modulation (SPM) is induced. In optical heterodyne detection, SPM cannot be compensated for by the delay equalizer (electrical domain) used to compensate fiber chromatic dispersion. However, the transmission distance limitation of multi-repeatered coherent transmission systems has not been investigated in the presence of SPM. This paper theoretically and experimentally investigates the transmission distance achievable with a phase-shift-keying (PSK) heterodyne detection system employing in-line optical amplifiers and delay equalization. The calculated results show that equalization is effective when γP0/2B2|β2|<10 in the normal dispersion regime, and γP0/2B2|β 2|<15 in the anomalous dispersion regime. Furthermore, the increase in transmission distance achieved by using equalization is experimentally shown in an 8 Gb/s PSK heterodyne transmission experiment using a conventional single-mode (SM) fiber and in-line fiber amplifiers 相似文献
3.
In optical fiber communication systems using Er3+ doped fiber amplifiers operating in their compression region, the optical signal power is known to be restored by the self-healing effect in the case of the span loss increase. In this paper, the influence of such excess loss on the system transmission performance is experimentally and numerically investigated from the point of view of the system signal-to-noise ratio and Q-factor. The results show that the system SNR is not completely recovered although the signal power is restored after several stages of amplifiers and that there exists the residual degradation of the system SNR. Through a 5.3 Gb/s data transmission experiment over 3000 km, the transmission penalty due to the excess span loss is confirmed to be decided by this residual degradation of the system SNR. The obtained results can be used for system design and a plan of maintenance for the optical amplifier communication system 相似文献
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Group-velocity dispersion (GVD) compensation in in-line amplifier systems is evaluated from the viewpoint of improving the transmission distance. The nonlinear Schrodinger equation, which simulates signal propagation in optical fibers, is numerically evaluated to clarify the optimum configuration for GVD compensation. It is shown that the optimum amount of GVD compensation is about 100% of the GVD experienced by the transmitted signal. The optimum compensation interval is found to be a function of the bit rate, signal power, and dispersion parameter. For dispersion parameter values ranging from about -0.1 ps/nm/km to -10 ps/nm/km, and an amplifier noise figure of about 6 dB, the optimum compensation configuration can eliminate the GVD from in-line amplifier systems, thus improving transmission distances to those limited by self-phase modulation and higher-order GVD 相似文献
6.
级联光放大器通信系统中的信噪比变化 总被引:2,自引:0,他引:2
我们从计算掺光纤放大器输出的光子数的起伏入手,得到了适用于各种工作状态的单个EDFA输出信噪比表达式,由此分析了级联光放大器通信系统中的信噪比变化,并与前人的工作进行了比较。 相似文献
7.
电流比值误差和相位误差是检验互感器的重要指标,噪声对其有较大影响.光纤电流互感器不同于传统电流互感器的重要特征之一即是存在较大噪声,在测量小电流时表现尤为显著,已经成为阻碍光纤电流互感器实用化进程的重要难题.分析了高斯白噪声背景下电流比值误差和电流相位误差的统计特征,研究了0.2S级下电流互感器数字输出信号信噪比所需满足的条件,探讨了电流互感器信噪比的计算方法以及影响信噪比的因素,并设计实验验证了理论分析的正确性.分析表明,为满足0.2S级光纤电流互感器信噪比需达到136,在额定电流以及数据更新率一定的情况下,仅有通过降低噪声以及增加敏感线圈缠绕圈数的方法可以提高系统信噪比. 相似文献
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光开关在分布式光纤温度传感系统的应用研究 总被引:2,自引:2,他引:0
分析了决定分布式光纤温度传感器系统传感距离的因素,提出了使用光开关扩展系统的传感长度。设计了多模1×2棱镜光开关的单片机驱动接口,计算机软件通过RS232串行接口发出指令控制光开关的切换。测试结果表明,嵌入了1×2光开关可使系统传感光纤长度延伸为原来的2倍。 相似文献
9.
A simple method of alternatively using high-inversion and moderate-inversion erbium-doped fiber amplifiers (EDFA's) in an optical amplifier chain is presented to mitigate the self-filtering effect and equalize both signal power and signal-to-noise ratio (SNR) of multiple wavelength channels in wavelength-division multiplexing (WDM) transmission systems. The performance of the compensated system with alternatively used high- and moderate-inversion amplifiers is compared with the uncompensated ones where only moderate- or high-inversion amplifiers are employed. The result shows that the compensated system has a flatter gain profile, a lesser signal power spread, and SNR degradation 相似文献
10.
D. Alzetta M. Matsumoto 《Photonics Technology Letters, IEEE》2003,15(6):822-824
We numerically evaluate the performance of two kinds of distributed polarization-mode dispersion compensation techniques using either linear or elliptic variable polarizers. Each in-line compensator is characterized by only one or two degrees of freedom and the average power is used as a monitor signal, which simplifies the control algorithm. The use of polarizers causes inevitable attenuation of the optical signal, which induces additional noise in amplified systems. Nevertheless, the noise enhancement due to the distributed polarizer-induced loss is shown to be limited in systems operated with erbium-doped fiber amplifiers in gain saturation and the tolerable differential group delay can be improved if the frequency of insertions is increased. 相似文献
11.
David Poe Sanghyun Woo Hyoungsoo Kim 《Analog Integrated Circuits and Signal Processing》2013,75(3):483-490
Consumer electronics are experiencing an explosive growth in bandwidth requirements. This growth is driven by demand for fiber-to-the-home Internet connections, the increasing capabilities of in-home consumer devices as well as the demands of multimedia recording and playback in mobile devices. However, traditional copper channels and previous generations of optical fiber experience dispersive effects at data rates above 1 Gbps, leading to inter-symbol interference (ISI). This paper presents a finite impulse response filter-based feed forward equalizer (FFE) to reduce the effect of ISI on these channels. The efficacy is of the FFE is demonstrated by measuring the eye diagrams of a 10 Gbps signal transmitted through an optical fiber as well as a copper backplane with and without FFE compensation. The proposed FFEs successfully compensate ISI for both the optical and copper backplane links. All circuits are fabricated using a 0.18 μm CMOS process. 相似文献
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本文对陆上级联接掺铒光纤放大器(EDPA)波分复用光纤通信系统中国波混频所造成的各个光信道光信噪比的恶化提出了一套计算方法,并结合常规单模光纤及一种特殊设计的色散位移光纤进行了分析计算。结果表明:在四波混频所引入的光信噪比恶化中,因新生频率分量导致的噪声增加一般远大于光信号功率的减弱。不等信道间隔划分能有效地避免四波混频的影响,而光滤波器的带宽应在允许范围内尽量压窄。对采用色散补偿技术的级联EDFA波分复用系统,在同一光中继段内,使常规单模光纤置于特殊设计的色散位移光纤之前,能进一步减少四波混频带来的光信噪比的恶化。 相似文献
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Qun Shi 《Communications, IEEE Transactions on》1995,43(6):2077-2084
Performance analysis for a hybrid subcarrier-multiplexed (SCM) AM/QAM transmission over an optical fiber is presented. It is shown that the bit-error-rate (BER) of M-ary QAM in such hybrid systems can be significantly affected due to occasional laser “clipping” of the SCM signal. Here we analytically determine the asymptotic distribution of the clipping noise by modeling it as a Poisson impulse train. The BER of M-ary QAM is then evaluated in terms of optical modulation indices of M-ary QAM and AM signals which in turn specify signal-to-noise ratio (SNR), impulsive index (clipping index) of the clipping noise, and power ratio of the Gaussian noise to the clipping noise. Numerical examples are given and compared with experimental data with reasonably good agreement for small SNR's. The results have application for estimating the BER's of digital signals for SCM analog/digital transmission over an optical fiber and for employing appropriate error correction codes and/or optimum receiver design for such environments 相似文献
16.
This paper presents a method for determining the probability of rare events, in particular for probability density function (pdf) and bit error rate (BER) estimation. The derivation of the method is based on the presumption that the pdf is a member of a family of distributions very often named as the generalized exponential (GE) class of distributions. Based on high reliability estimations obtained in short simulation/measurement times, the low probably events are estimated accurately by extrapolation. The suggested method can be applied to some distributions that are different from GE distributions, such as noncentral chi-square distributions, to extrapolate to low probability events, with some extrapolation error. It can also be applied to BER estimation. The method is in particular helpful for estimating channels suffering from both severe signal distortion causing undesired intersymbol interference (ISI) of several symbols, and from severe noise. Such conditions prevail, for example, in metro and long haul high-speed optical fiber communication systems. So the method may be implemented in particular in maximum-likelihood sequence estimation (MLSE) optical receivers using nonparametric channel model estimation. A special use of the extrapolation method is explained for practical systems using trellis branch metrics derived from the estimated pdf to decode the transmitted sequence of symbols. 相似文献
17.
Uchiyama K. Morioka T. Kawanishi S. Takara H. Saruwatari M. 《Lightwave Technology, Journal of》1997,15(2):194-201
This paper investigates experimentally and theoretically the signal-to-noise ratio (SNR) characteristics of 100 Gb/s all-optical demultiplexing using a nonlinear optical loop mirror (NOLM). The analysis takes into account two effects that degrade the SNR associated with NOLM demultiplexing. First is channel crosstalk originating from the leakage of nontarget channels. Second is the intensity fluctuations of demultiplexed signals caused by the combined effects of timing jitter and a profile of the switching window. Considering these two effects, power penalties associated with NOLM. Demultiplexing are theoretically evaluated using the conventional noise theory of an optical receiver followed by an optical preamplifier. Experimental results of bit error rate measurements for 100 Gb/s demultiplexing using three different NOLMs with different intrinsic crosstalk values, defined by signal transmittance in the absence of control pulses, show that the power penalties are in good agreement with the evaluation based upon our proposed analysis. It can be found from our investigation in demultiplexing from 100 to 10 Gb/s that intrinsic crosstalk of less than -25 dB, corresponding to a coupling ratio, K, of |K-0.5|⩽0.03, is required for the power penalty of less than 1 dB. The root-mean-square (rms) value of the relative timing jitter necessary for obtaining a sufficient timing tolerance width for combining control and signal pulses is determined 相似文献
18.
Optical time domain reflectometry (OTDR) in an optical transmission line containing in-line Er-doped fiber amplifiers is investigated. The proposed Er-doped fiber amplifiers are based on optical circulators, which support both OTDR and digital signal transmission. The measurable limit of OTDR fault location in optical transmission lines containing in-line amplifiers is discussed. Fault location and 1.8-Gb/s digital signal transmission are demonstrated in a 316.9 km, optical transmission line constructed with three in-line Er-doped fiber amplifiers 相似文献
19.
By using a double-sideband suppressed carrier (DSB-SC) optical transmitter and a remote self-heterodyned (RSH) detection method, we experimentally and analytically proved the feasibility of a radio-over-fiber system using a 16-QAM signal at 5 Gb/s and 18 GHz, with a transmission distance of 100 km between a mobile service center and a base station. The transmission system performance was carefully analyzed by considering optical amplifier noise, fiber nonlinearity, phase noise, frequency response, and analog-to-digital converter (ADC) quantization noise. The 18-GHz, 16-QAM signal can be radiated from the base station to a remote antenna port without any upconverter, and the remote antenna port consists of a downconverter and high-speed digital signal processors (DSPs) to recover the 16-QAM signal. The high-speed DSP, which partially compensates the intersymbol-interference (ISI) and phase-noise-induced system penalties, was enabled by 20-Gs/s ADCs. The algorithms used in the DSP blocks were also described in details. 相似文献
20.
Farre J. Bodtker E. Jacobsen G. Stubkjaer K.E. 《Photonics Technology Letters, IEEE》1992,4(12):1354-1357
The authors present detailed results concerning the dynamic range of an amplitude-shift keyed (ASK) heterodyne optical communication system where the transmitted signal is impaired by significant amounts of laser phase noise. Theoretical results are evaluated for a system with up to ten in-line optical amplifiers and a significant influence of the laser phase noise is found for the maximum allowable transmission span and the dynamic range. With ten amplifiers, a linewidth of 11% of the bit rate causes the span to be reduced by 12.2 dB and the dynamic range to be reduced by 5.7 dB. The results have been confirmed using two amplifiers in a field trial experiment at a bit rate of 636 Mb/s with an IF linewidth of 70 MHz 相似文献