单模光纤与多模光纤的色散

色散是光纤的传输特性之一。由于不同波长光脉冲在光纤中具有不同的传播速度,因此,色散反应了光脉冲沿光纤传播时的展宽。光纤的色散现象对光纤通信极为不利。光纤数字通信传输的是一系列脉冲码,光纤在传输中的脉冲展宽,导致了脉冲与脉冲相重叠现象,即产生了码可干扰,从而形成传输码的失误,造成差错。为避免误码出现,就要拉长脉冲间距,导致传输速率降低,从而减少了通信容量。另一方面,光纤脉冲的展宽程度随着传输距离的增长而越来越严重。因此,为了避免误码,光纤的传输距离也要缩短。光纤的色散可分为：     

单模光纤测量技术(之一)——单模光纤的色散测量方法

光纤的传输损耗和色散是限制光纤通信中传输距离的主要因素。而色散又是限制光纤通信系统传输带宽的决定性因素,因为色散使在光纤中传输的光脉冲随着传输距离的增加而展宽。在单模光纤中,脉冲展宽主要起源于折射率随波长变化所引起的模内材料色散和单个模的群速度随频率略有变化所导致的波导色散。因此单模光纤的总色散,或者说波长色散或色度色散,主要就包括这两部分。单模光纤色散的测量对于研究单模光纤的传输特性,控制和改进预制件的质量;监测单模光纤通信系统的性能具有很大的理论意义和实用价值。本文主要介绍国内外单模光纤色散测量的各种方法及其特点。     

高阶色散和高阶非线性效应对准光孤子传输的影响

为了研究高阶色散和高阶非线性效应对其在普通光纤上传输的影响,用数值模拟的方法研究了三阶色散、自陡效应和脉冲内拉曼散射效应对准光孤子传输的影响.结果表明准光孤子在实际的普通光纤中传输时,三阶色散、自陡效应和脉冲内拉曼散射效应中,冲内拉曼效应对其传输产生的影响比较大,致使准光孤子在普通光纤上传输时脉冲不断展宽,脉冲峰值功率降低,不能长距离保持脉冲形状不变.     

光纤有线电视技术入门30问(6)

问7:什么是光纤的色散?在答6中的 SI 型多模光纤中,稍微谈到了因各个模式的群速度不同而发生的多模色散。后来在 SM 型光纤又触及到结构色散。当入射的光信号经过光纤传输以后,凡出射端解调后光脉冲发生时间展宽(指数字式脉冲)或检波后电平随信号频率增高而降低(指模拟调制波形信号)的现象则称为色散。     

波分复用系统中混合色散补偿方案的研究

色散补偿机制限制了光纤通信系统中传输信号的脉冲展宽效应.为了限制脉冲展宽效应,提出了一种针对波分复用光纤传输系统的两种色散补偿技术相结合的方案,对线性啁啾光纤光栅(CFBG)和色散补偿光纤(DCF)的色散补偿方案进行了建模分析,在波分复用系统(WDM)中采用干路DCF分波后支路CFBG相结合的方案与传统前置色散补偿方案...     

色散补偿准光孤子传输特性数值分析

为了使准光孤子能够在标准单模光纤中稳定地传输,采用了分步傅里叶方法分别模拟了准光孤子在标准单模光纤中的传输和在色散补偿系统中的传输,得到了准光孤子在标准单模光纤中的传输特性和在色散补偿系统中的传输特性。结果表明,准光孤子在标准单模光纤的传输过程中脉冲峰值逐渐降低,脉冲宽度逐渐展宽,不能稳定传输;而准光孤子在采取色散补偿技术的色散补偿系统中传输时,脉冲形状几乎保持不变,与准光孤子直接在标准单模光纤中的传输相比,性能得到了很大改善。     

超高速光纤通信中的色散补偿技术

随着全光网络建设的推进,光传输系统中传输速率的提高和信号传输带宽的增加,使色散问题变得日益突出.在当前已经大量铺设的常规光纤G.652线路中,零色散点位于1310nm,在1550nm处时具有较大的色散系数(约17ps/nm/km),当光脉冲信号经过长途传输后,由于不同波长的传输速度不一致,光纤色散值的积累引起脉冲展宽,将导致严重的码间串扰,使接收端产生误码,从而使传输特性变坏.光纤色散补偿技术的研究和发展,对提高目前已经铺设的常规光纤通信系统容量提升具有尤其重要的意义.     

弱非线性在零色散波长处对光信号的影响

文章得出在零色散波长处二阶色散为零时，光信号在弱非线性与三阶色散的共同作用下的频域级数解，得出了高斯脉冲在光纤中传输时的近似频域表达式，并利用数值积分方法出时域波形与脉冲展宽因子演化图。     

单模光纤色散测量(下)

三、频域测量技术前节中,我们把色散测量归结为观察光脉冲通过光纤时的脉冲展宽或脉冲时延,这种利用光脉冲的技术总称为时域测量技术.另一种测量光纤色散的方法,是利用正弦波调制光源,且常用频域测量技术这一术语来表述. 在多模光纤的频域测量中,常用扫频测量技术,即     

超高速光纤通信中的色散补偿技术

随着全光网络建设的推进,光传输系统中传输速率的提高和信号传输带宽的增加,使色散问题变得日益突出。在当前已经大量铺设的常规光纤G.652线路中,零色散点位于1310nm,在1550nm处时具有较大的色散系数(约17ps/nm/km),当光脉冲信号经过长途传输后,由于不同波长的传输速度不一致,光纤色散值的积累引起脉冲展宽,将导致严重的码间串扰,使接收端产生误码,从而使传输特性变坏。光纤色散补偿技术的研究和发展,对提高目前已经铺设的常规光纤通信系统容量提升具有尤其重要的意义。     

Dispersion Measurement in Optical Fibers Using Supercontinuum Pulses

The chromatic dispersion of an optical fiber is measured using a time-of-flight technique, based on temporally and spectrally resolving a dispersed broadband pulse, on which a spectral fringe pattern has been imposed using an etalon. The technique employs broadband supercontinuum radiation, generated by launching picosecond pulses from a fiber laser into a photonic- crystal fiber. It allows the dispersion of highly dispersive optical fibers and components to be measured with a high spectral resolution over a wide wavelength region. The technique is demonstrated by measuring the dispersion of a dispersion-compensating module over its entire 400-nm transmission band with a subnanometer spectral resolution.     

Fiber chromatic dispersion equalization at the receiving terminalof IM-DD ultra-long distance optical communication systems

We have evaluated the effect of fiber chromatic dispersion equalization at the receiving terminal for transoceanic optical communication systems. We used a 1000-km fiber loop with 31 Er-doped fiber amplifiers for the experiments, and measured the bit-error-rate characteristics after 9000-km transmission. Accumulated chromatic dispersion originating from the discrepancy between the signal wavelength and the system zero dispersion wavelength was equalized by the equalization fiber at the receiving terminal. We used both normal and anomalous dispersion fibers at the receiving end. The results have shown that the equalization method of the fiber chromatic dispersion at the receiving terminal is useful with some limitations for ultra-long distance optical communication systems     

48 fs,108 MHz色散管理孤子掺Er3+光纤激光器

提出了一种基于商售光纤构建的适用于精密光谱光频梳应用的100 MHz重复频率色散管理孤子光纤激光器的设计方案.通过采用低负色散光纤调控重复频率、高正色散光纤增大腔内脉冲呼吸比,构建了重复频率为108 MHz、中心波长为1550 nm的基于正色散掺铒光纤的色散管理孤子光纤激光器,该激光器腔内净色散为-0.0023 ps2,直接输出脉冲宽度为70 fs,经光纤压缩后脉冲宽度为48 fs,且脉冲中心波长处在1550 nm.     

Single-channel transmission in dispersion management links inconditions of very strong pulse broadening: application to 40 Gb/ssignals on step-index fibers

The dynamic behavior of single-channel transmission on standard fibers with strong dispersion management has been theoretically and numerically analyzed. A single pulse and a pseudorandom pulse sequence have been compared in order to highlight the relevant role played by pulse interaction. A semianalytical theory of the bandwidth evolution demonstrates that the introduction of prechirp is very important for controlling the single pulse propagation and numerical results show that such a chirp also permits to limit the nonlinear pulse interaction when other pulses are present. Simulations of a 40 Gb/s return-to-zero (RZ) system operating in links encompassing step-index fibers, by adopting a periodical compensation of the chromatic dispersion have been performed and results show that a record distance of 1300 km can be achieved with an amplifier spacing of 100 km. A compensation of the fiber third order dispersion would extend the transmission to 1800 km, which corresponds to the limits imposed by the amplified spontaneous emission (ASE) noise of the optical amplifiers     

海底光缆用色散均衡光纤

介绍了一种带正色散的单模光纤,用来均衡常用于海底光缆中的非零色散位移光纤的负色散。这种光纤类似于常规单模光纤（Ｇ．６５２光纤）,但具有较低的衰减和较小的宏弯损耗。由于这种光纤应用常规的掺锗纤芯和纯ＳｉＯ２包层,与目前常用的纯ＳｉＯ２纤芯和掺氟包层的色散均衡光纤相比,在成本上具有较大的优越性。     

Investigation into the temperature dependence of chromaticdispersion in optical fiber

The change in the chromatic dispersion of optical fiber with temperature is an important design parameter for 40-Gb/s systems. We derive an equation for the change in dispersion with a temperature that is more general than what has previously been published. We present experimental results for the change in fiber dispersion with temperature for six commercially available fiber types of interest for 40-Gb/s communication systems. In addition, we demonstrate that the empirical model developed by Ghosh et al in 1994 for the temperature-dependent index of refraction of SiO₂ can be used to accurately model the temperature dependence of the chromatic dispersion of a wide variety of optical fibers     

First sea trial of 1.5-μm submarine optical fiber cable

The first sea trial of submarine optical fiber cable using dispersion-shifted fibers is described. The discussion covers the fiber structural design, cable manufacturing results, fiber splicing, cable laying results, and a high-accuracy measurement technique for optical loss and chromatic dispersion. The results demonstrate the feasibility of long-span, high-capacity 1.5-μm submarine optical fiber cable     

Chromatic dispersion measurement in graded-index multimode opticalfibers

The chromatic dispersion observed in a graded-index multimode optical fiber is a function of the radial position of the launched light. When a graded-index multimode optical fiber is overfilled spatially and angularly, the chromatic dispersion observed is an average (composite) chromatic dispersion over all of the possible launches. Under certain assumptions, the relationship between the chromatic dispersion observed for the overfilled fiber and the chromatic dispersion of any restrictive launch can be determined. This relationship can be used to predict the composite graded-index multimode optical fiber chromatic dispersion from the measurement of the chromatic dispersion of a single simplified launch, such as a single-mode fiber launch. Preliminary experimental results confirm this approach     

Performance evaluation of the different types offiber-chromatic-dispersion equalization for IM-DD ultralong-distanceoptical communication systems with Er-doped fiber amplifiers

We have evaluated the transmission performance of different fiber-chromatic-dispersion-equalization methodologies for ultralong distance IM-DD optical communication systems that use Er-doped fiber amplifier repeaters. The experiment used a 1000 km fiber loop consisting of 30 dispersion-shifted fiber spans and 31 Er-doped fiber amplifiers. We changed the insertion point of the normal single-mode fiber for equalization to change the shape of the accumulated chromatic dispersion. Comparison of the longest transmission distance and the width of the 9000 km transmissible window are discussed for several types of dispersion equalization. The results indicate that the best type of the dispersion equalization for ultralong distance IM-DD optical communication systems is to install dispersion-shifted fibers with short sections of normal single-mode fibers to compensate the accumulated dispersion     

利用光脉冲传输特性抑制偏振模色散

基于双折射光纤中光脉冲传输方程,详细分析了二阶色散、自相位调制以及交叉相位调制在光脉冲传输过程中引起的啁啾。分析结果显示:通过合理选取入射功率,二阶色散引起的啁啾与自相位调制引起的啁啾在脉冲中心附近可以相互抵消,从而使脉冲展宽最小;交叉相位调制产生的两偏振分量的啁啾引起的频移,可使两偏振分量间产生互束缚,利用这种现象可以抑制偏振模色散。