共查询到18条相似文献,搜索用时 125 毫秒
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为了降低MZM对模拟信号产生的非线性影响,提出了一种基于RoF系统的以三角波作为副载波的信号传输方案.该方案采用线性度高的三角波携带基带数据并经过MZM调制.调制后的光信号可以在RoF系统的接收端通过直接检测得到余弦形式射频信号,该射频信号几乎不存在由于MZM的非线性调制引起的边带分量.仿真分析了在直接调制和间接调制的... 相似文献
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实验研究了一种基于相位调制器(PM)并级联强度调制器(IM)实现40 GHz毫米波传输正交频分复用(OFDM)信号的光纤无线通信(ROF)系统。在中心站,采用20 GHz的射频(RF)信号驱动PM,调节驱动信号的强度,使输出的信号经光纤布拉格光栅(FBG)滤除中心载波后再送入IM。2.5 Gbit/s的OFDM信号直接调制在光毫米波上,经过50 km标准的单模光纤(SSMF)传输到基站。在基站,光调制信号经光电转换器(PD)转换成电调制信号,再与RF信号混频,恢复出基带OFDM信号。实验结果表明,在无色散补偿、误码率(BER)为10-3的条件下,下行链路中2.5 Gbit/s的OFDM信号经光纤传输50 km后,其功率代价小于1 dB,而且信号的星座图依然较好。 相似文献
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OFDM在长距离光传输系统色散补偿中的应用 总被引:3,自引:1,他引:2
为了降低光纤长距离传输中电域色散补偿(EDC,Electronic Dispersion Compensation)的实现复杂度,采用正交频分复用技术(OFDM,Orthogonal Frequency Division Multiplexing)与光单边带调制(OSSB,Optical Single Sideband),可有效实现光纤的色散补偿。文章介绍了基于光直接检测(DD,Direct-Detection)的OFDM系统,重点对系统色散补偿的实现进行了具体的数学分析,并进行了数字仿真,就系统误码率(BER)与传统光传输系统(NRZ,Non-Return-to-Zero)进行了比较。结果表明,较传统光传输中电域色散补偿,基于光直接检测的OFDM系统色散补偿实现简单,系统复杂度降低,同时也提高了系统性能。 相似文献
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为提高光载无线(radio over fiber,RoF) 传输系统中的光波信号的利用率,本文提出了一种基于两个平行马赫-增德尔调制器 (Mach-Zehnder modulator,MZM) 的RoF传输系统。两个平行MZM经射频(radio frequency,RF) 信号调制后,产生5个光边带信号,分别是正负一阶光边带、正负二阶光边带和光载波。其中正负二阶光边带使用基带数据进行调制,经光电检测器(photodiode,PD) 拍频后产生已调数据的毫米波信号,再由天线发射出去。正二阶边带和光载波经PD拍频后产生未调制数据的毫米波,该毫米波用于接收端解调的本振信号(local oscillator,LO) 。负二阶边带信号用于上行链路的光载波。在本系统中,5个光边带信号都被充分利用,提高了光信号的利用效率。此外,还分析了该系统通过色散介质的传输特性,为RoF通信系统提供了一种实用化的解决方案。 相似文献
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为了减小光纤的色度色散对光纤正交频分复用(OFDM)系统性能的影响,提出了将无线通信中的信道估计器引入光纤OFDM系统进行信道估计的色散补偿方法。在理论上分析了光纤的色度色散对于传输OFDM信号的影响,并在实验中采用梳状导频的形式,在每个OFDM码元的特定的子载波上插入导频,在接收端通过基于最小平方(LS)原则的LS估计器进行信道估计,得到了OFDM光纤传输的信道幅度响应和相位响应,通过使用LS估计器,直接调制的光OFDM信号在单模光纤中传输200km,误比特率低于10-6 ,功率代价小于2dB。结果表明,高频子载波较低频子载波更容易受到色散的影响,在光纤OFDM系统中引入信道估计器进行信道估计能够有效补偿由色度色散带来的相位偏移和幅度衰减。 相似文献
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《Lightwave Technology, Journal of》1996,14(3):261-272
In this paper long distances very high capacity NRZ optical transmission systems adopting direct detection are considered in links with a low average chromatic dispersion. Particular attention is devoted to polarization modulated (PM-DD) systems. Polarization modulated systems results to he more degraded with respect to intensity modulated (IM-DD) systems by the light depolarization induced by the interplay among the Kerr effect, the ASE noise of the optical amplifiers and the polarization mode dispersion. The light depolarization is particularly strong in conditions of large spectral broadening that are met when the chromatic dispersion value is maintained very low along the link. On the other hand the use of a fluctuating chromatic dispersion with a mean value equal to zero, whereas the local dispersion is different from zero, shows the double advantage to reduce the chromatic dispersion impairments and to limit the spectral broadening. The advantages offered by this dispersion management technique have been already shown in several experiments for IM-DD systems: in this work we show that this technique is very important also for PM-DD systems since the limitation in the spectral broadening reduces the light depolarization. We show that adopting a suitable dispersion management and an opportune preamplifier optical filter transmissions at 5 Gb/s can be attained in transoceanic links by means of FM-DD systems 相似文献
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Chromatic dispersion induced distortion of modulated monochromatic light employing direct detection 总被引:2,自引:0,他引:2
The spectrum of an intensity modulated (IM) and a combined intensity-frequency modulated (IM-FM) monochromatic light source has been generated. The amplitudes of the modulated carrier and the first three pairs of sidebands are plotted showing the influence of IM on an FM signal. The effects of first order chromatic dispersion on the baseband amplitude response and harmonic distortion are determined. The manner in which modulation type and depth, modulating frequency, wavelength, and fiber length alter harmonic distortion is presented. Numerical examples giving the amplitude response of a single-mode fiber system as well as the magnitude of the second- and third-harmonic distortion caused by chromatic dispersion are presented. Based on this material, the limits placed on analog transmission due to chromatic dispersion may be assessed. 相似文献
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The author reports the impact of chromatic dispersion in optical millimetre-wave systems operating in the 1.55 μm wavelength window. Experimental and theoretical results confirm the dramatical millimetre-power degradation in conventional amplitude modulated systems using for example, external optical modulators. In comparison, by use of a similar setup a self-heterodyne-based system concept has been investigated showing negligible dependence on the chromatic dispersion 相似文献
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为了建立一个基于888nm半导体抽运的高平均功率和高效率皮秒激光振荡器的理论模型,采用模拟计算方法和谐振腔理论、ABCD定律、自洽条件以及连续被动锁模条件,利用激光晶体Nd:YVO4对波长888nm半导体抽运源的吸收特性和元件的相关参量、合适的腔模参量、实现稳定锁模的参量进行了理论分析和计算,并通过以上研究和模拟计算得到了皮秒振荡器模型的相关数据。结果表明,在120W的抽运功率下,激光器可以输出约61.5W的皮秒激光,光光转换效率51.3%。这一理论模型的建立对高平均功率和高效率皮秒激光振荡器的实验研究起着指导作用。 相似文献
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Vodhanel R.S. Elrefaie A.F. Iqbal M.Z. Wagner R.E. Gimlett J.L. Tsuji S. 《Lightwave Technology, Journal of》1990,8(9):1379-1386
A comparison is presented of the performance of amplitude-shift-keying (ASK), frequency-shift keying (FSK), and differential-phase-shift-keying (DPSK) lightwave systems which operate at 10 Gb/s with directly modulated 1550-nm distributed feedback (DFB) laser transmitters and conventional 1310-nm dispersion-optimized fiber. Computer modeling techniques were used to accurately simulate the amplitude modulation response and the frequency modulation response of DBF lasers. The system performance is evaluated from simulated eye patterns for both direct and heterodyne detection. With the narrow-optical spectral widths of these signal formats, fiber chromatic dispersion limits up to 70 km were obtained for transmission at 1550-nm using conventional 1310-nm optimized fiber 相似文献
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《Optical Fiber Technology》1999,5(2):165-174
We investigate the impact of fiber chromatic dispersion on the performance of an externally modulated millimeter-wave fiber-radio system incorporating a broadband radio direct-sequence code division multiple access (DS-CDMA) scheme. In particular, we investigate the effect of dispersion on DS-CDMA signals with regard to CDMA code rate, center frequency, and modulator chirp. We show that the spreading of the signal spectrum using DS-CDMA can result in significant reductions in data amplitude variations normally experienced in externally modulated millimeter-wave fiber-radio systems. We also demonstrate the successful transmission of a 10-Mb/s data channel over a 39-GHz fiber-radio link employing DS-CDMA and consisting of 25 km of standard optical fiber and a 1-m radio link. 相似文献
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The impact of chromatic dispersion on the system limitation due to polarization mode dispersion (PMD) is investigated through Monte Carlo simulations. The waveplate model is used to realistically simulate the variation of PMD with frequency. It is shown that the effects of higher order PMD are compounded in the presence of chromatic dispersion. This can lead to a reduction in the PMD limit for large values of chromatic dispersion. However, it does not lead to a reduction in the PMD limit for the moderate levels of chromatic dispersion that would be encountered in most systems 相似文献