Dispersion flattened transmission line consisting of wide-band non-zero dispersion shifted fiber and dispersion compensating fiber module

The transmission line consisting of non-zero dispersion shifted fibers (NZ–DSFs) and dispersion compensating fiber (DCF) modules has been proposed to enable the wide-band wavelength division multiplexing (WDM) transmission. The NZ–DSFs with the effective area over 60 μm² and the dispersion of +5–11 ps/nm/km (1500–1600 nm) have been developed to suppress the transmission penalty caused by the four-wave mixing. The DCF modules which compensate for the dispersion and the dispersion slope simultaneously have also been realized. To enhance the figure of merit (FOM) of the DCF by enlarging the absolute value of its dispersion is found to be an effective way to reduce the non-linear effects occuring in the DCF. The transmission line actually fabricated based on the optimized design exhibits an extremely low dispersion deviation of ±0.08 ps/nm/km in the C band.     

WDM+EDFA+DCF光纤传输系统中色散补偿方案的分析

由于在ＷＤＭ＋ＥＤＦＡ光纤传输系统中使用常规单模光纤（ＳＭＦ）在１５５０ｎｍ窗口的大色散限制了传输距离,采用色散补偿光纤（ＤＣＦ）进行色散补偿是上前一种较为理想的方法。本文基于光纤ＷＤＭ＋ＥＤＦＡ＋ＤＣＦ的长距离传输系统,讨论了ＤＣＦ色散补偿对光纤非线性效应交叉相位调制和四波混频（ＦＷＭ）的影响,提出了采用ＤＣＦ集总、后置、非完全补偿的色散补偿方案,这种方案可合系统具有更佳的传输性能。     

DCF光纤拉曼放大器的实验研究

DCF(dispersion compensating fibre)光纤具有较高的拉曼增益系数,利用这一点可以用较短长度的DCF光纤制成分立式的光纤拉曼放大器,作为传输线路上的损耗补偿.本文在测量并计算了DCF光纤的拉曼增益系数的基础上,对分立式的DCF放大器的开关增益和噪声指数进行了测量和分析,并将分立式FRA和分布式FRA在开关增益和噪声指数方面做了比较。介绍了用不同的测量方法所造成的实验结果的差异.实验结果表明,放大介质为5 km的DCF光纤所构成的放大器,在抽运功率为800 mW的条件下,最大增益可达14.77dB,3 dB带宽为35 nm,满足作为损耗补偿的要求.     

Dispersion-compensator incorporated optical fiber amplifier

An optical fiber amplifier incorporating a dispersion compensator such as a dispersion compensating fiber (DCF) is proposed and examined theoretically and experimentally. The new amplifier requires only a single pump laser. In the experiment a 0.98-μm laser diode was used and the pump power was 50 mW. By utilizing remnant pump power, the amplifier can halve the loss effect of the compensator and double the apparent figure of merit of the DCF (ps/nm/dB). The noise figure of the new amplifier is not affected by inserting the DCP. A low-noise figure of 5 dB was obtained over a wide input-power range of -40 to -10 dBm     

光子晶体光纤在光通信中的色散补偿应用

通过合理设计可使光子晶体光纤具有较大的负色散,利用这一特性可以制作新型光纤器件,用于现代光纤通信系统的色散补偿,这可大大缩短色散补偿光纤的长度。阐述光子晶体光纤在现代宽带光通信系统的色散补偿技术中的应用潜力,并说明如何设计光子晶体光纤的几何结构来补偿目前商用光通信系统中传输光纤的色散。     

基于FDTD方法的光子晶体光纤色散特性分析

基于电磁场时域有限差分法(FDTD)计算光子晶体光纤(PCF)的方法, 分析了运用该方法时需要注意的一些问题, 特别是关于晶格位置、晶格上各个电磁场分量的分布以及完全匹配层(PML)中在边界处的电磁场的处理。以此为理论依据分析了一种纯石英材料双层芯PCF, 对这种光纤的传输特性进行了详细的数值模拟。通过调整光纤的结构参数, 设计出大负色散值的宽带色散补偿光子晶体光纤(DCPCF)。数值模拟结果显示在1530～1565 nm波长范围内其色散值在-400和-600 ps/(km·nm)之间变化, 达到了具有相同有效模面积的普通色散补偿光纤(DCF)的5倍。在整个C波段可以有效补偿长度25倍以上的标准单模光纤(SMF), 其色散剩余量在±1.0 ps/nm·km以内。该种结构的PCF对于制作高增益和宽带色散补偿于一体的集中式光纤放大器具有十分重要的意义。     

基于DCF长距离光纤通信系统的色散补偿

通过介绍光纤色散的产生及其对传输系统的影响,引出了色散补偿技术.在多种色散补偿方法中,侧重探讨了色散补偿光纤(DCF)技术.基于DCF在标准单模光纤上传输2245 km的情况下进行了研究,获得了一些对实际色散补偿系统有参考价值的结论.     

光纤通信系统色散补偿方案的优化

为了优化光纤通信系统色散补偿方案,采用软件仿真的方法设计了一个用色散补偿光纤进行色散补偿的单信道通信系统,利用光纤环形镜的全反射特性使该系统的色散补偿方案得到了优化,补偿效果良好,并节约了成本。对色散补偿及光纤环形镜的工作原理进行了理论分析和仿真验证,取得了系统在2.5Gbit/s和10Gbit/s下Q参量和眼图的仿真数据,分别找出了两个信号速率下的系统最佳输入功率。结果表明,系统在2.5Gbit/s下的最佳输入功率为13dBm,此时Q参量达到了172.88;系统在10Gbit/s下的最佳输入功率为6dBm,其相应Q参量为45.96。这一结果对实际应用中光纤通信系统的色散补偿是有帮助的。     

Channel addition/removal response in Raman fiber amplifiers: modeling and experimentation

In this article, we investigate, both theoretically and experimentally, transient effects in Raman fiber amplifiers (RFA) caused by channel addition/removal. A comprehensive large-signal numerical model of RFA, which incorporates time variation effects and the downstream and upstream propagation of multiple signals, pumps, and amplified spontaneous emission components, has been used for the theoretical analysis. The effect of pumping scheme, pump power, the length and type of Raman fiber, and number of added and/or dropped channels on the dynamics of surviving channel power fluctuations has been studied. In our experimental setup, signals from two laser diodes (LDs) were transmitted through counterdirectionally pumped RFA consisting of 15.6 km of dispersion compensating fiber (DCF). To simulate channel addition/removal, one signal was square-wave-modulated at 500 Hz. At the output of the RFA, the signal of the continuous-wave LD was selected with an optical bandpass filter, and power fluctuations of the surviving channel were recorded with a high-speed digital oscilloscope. Power fluctuations as high as 0.45 dB with typical saturated amplifier overshoots were observed.     

8 × 10 Gb/s transmission system over 2 015 km with dispersion compensation by fiber Bragg Grating

The cascaded chirp fiber Bragg gratings（CFBGs） with ITU-T standard wavelengths and wavelength grid are applied to compensate the dispersion of 8×10 Gb/s WDM system. The ASE of the EDFA could be reduced, the OSNR of the transmitted signal can be increased and the fluctuation of the EDFA gain can be restrained in a certain scope by the CFBG employed in the system. Experiment of error-free 8×10 Gb/s 2015 km transmission without FEC and electric regeneration is demonstrated in this paper. In this system, only EDFA is used as amplifier,and no other form of dispersion compensator is adopted except CFBG. The experimental result showed that after 2 015 km transmission,the consistency of the dispersion compensating for each channel is perfect.     

啁啾光纤光栅补偿光纤色散的研究

啁啾光纤光栅被认为是目前最有实用价值的色散补偿方案之一。分析了啁啾光纤光栅补偿色散的基本原理,从简单模型出发分析了啁啾光纤光栅的色散补偿能力,用数值法研究了啁啾光纤光栅的时延及色散特性,并比较了变迹型与非变迹型啁啾光纤光栅。结果表明要获得较大的色散,要求光纤光栅有较长的长度和较小的啁啾。同时为了消除色散曲线的振荡还必须采取适当的变迹方法。     

一种采用光学相位分集接收技术的相干光正交频分复用远端接入系统

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。     

Cross-gain modulation in Raman fiber amplifier: experimentation and modeling

The effects of channel loss on the performance of Raman fiber amplifiers (RFA) are investigated both experimentally and theoretically. Signals from one distributed-feedback (DFB) laser and an external cavity laser (ECL) were transmitted through counterdirectionally pumped RFAs consisting of 15.6 km of dispersion compensating fiber (DCF). The ECL light was square-wave modulated at 500 Hz. At the output of the RFA, the signal of the modulated channel was eliminated with an optical band pass filter, and power fluctuations of the surviving channel were recorded with a high-speed digital oscilloscope. Power fluctuations as high as 0.45 dB with typical saturated amplifier overshoots were observed. The experimental results were confirmed by a large signal numerical analysis.     

10Gbit／s信号在光纤传输系统中的啁啾光纤光栅色散补偿

本文以１０Ｇｂｉｔ／ｓ在Ｇ．６５２光纤传输１１７０ｋｍ的光纤通信系统进行了研究，分别用色散补偿光纤和啁啾光纤光栅进行了色散补偿的计算机模拟实验，根据实验结果设计发符合系统要求的啁啾光纤光栅。     

System Stimulation for Dispersion Compensation with Nonideal Chirped Fiber Bragg Grating

Chirped fiber Bragg grating (CBG) has been used to compensate the dispersion in the optical fiber communication system. We substitute dispersion compensation fiber (DCF) with CBG in the 10Gbit/s disperion-managed system over 1100km. In order to get system performance in the nonideal situation, the parameters of CBG are varied from the designed optimum in some extent. Post-, pre- and dual-compensation methods are compared.     

基于OPC的高速PDM-CO-OFDM系统研究

通过理论分析和数值仿真,搭建了100Gbit/s的PDM(偏振复用)-CO-OFDM(相干光正交频分复用)系统,并使用OPC(光学相位共轭)技术对100Gbit/s的PDM-CO-OFDM系统的传输性能进行了补偿。研究表明,相位共轭技术不仅能够补偿系统的各阶色散,还能补偿非线性效应,使用OPC技术能使系统的传输距离达到1 200km,在最佳补偿距离上,使用OPC的系统Q值比使用传统的DCF(色散补偿光纤)的系统Q值大6.3dB。     

Optical fiber-based dispersion compensation using higher ordermodes near cutoff

Higher order spatial modes in optical fibers exhibit large, negative chromatic dispersion when operated near their cutoff wavelength. By using a spatial mode-converter to selectively excite a higher order mode in specially designed multimode fiber, this dispersion can be used to compensate the positive dispersion in conventional single-mode fiber spans. In this paper, issues related to compensating fiber and mode-converter design are explored. Experimental measurements in specially designed two-mode fibers operated in LP₁₁ mode show negative dispersion as large as -70 ps/nm·km at 1555 nm. Pulse propagation and system experiments employing spatial mode-converters to excite LP₁₁ mode in a two-mode fiber demonstrate the feasibility of this technique for dispersion compensation in lightwave systems     

色散补偿光纤的折射率剖面模型

提出了色散补偿光纤折射率剖面分布的通用模型。这一模型可用来设计色散补偿光纤的结构参数，也可用来分析纤芯折射是任意分布的匹配包层型光纤和W型光纤的传输特性，因而具有普遍的意义。     

Theoretical investigation of 8 /spl times/ 10-Gb/s WDM signal transmission performance based on gain-equalized SOAs using backward Raman pumping at DCF

We have theoretically investigated 8 /spl times/ 10-Gb/s wavelength-division multiplexing (WDM) signal transmission characteristics based on semiconductor optical amplifiers (SOAs) with equalized gain using discrete Raman amplification (DRA). Gain equalization and low noise figures have been obtained by adjusting the backward Raman pumping power and wavelength at a dispersion compensating fiber (DCF) for each span. Bit-error-rate characteristics were calculated for 8 /spl times/ 10-Gb/s WDM signal transmission over 6 /spl times/ 40-km single-mode fiber (SMF) + DCF links with gain-equalized SOAs using DRAs at DCF. Approximately a 2.5-dB improvement of the receiver sensitivity was achieved by using SOAs and DRAs with optimized Raman pumping. One can easily upgrade the transmission length of a link based on SOAs with an appropriate backward pump laser at each DCF.     

Wideband Hybrid Fiber Amplifier Using Er‐Doped Fiber and Raman Medium

In this paper, we report the experimental results of a hybrid wideband fiber amplifier. The amplifying medium is a concatenated hybrid fiber consisting of Er‐doped fiber (EDF) and dispersion compensating fiber (DCF). The gain mechanisms are based on stimulated emission in the EDF and stimulated Raman scattering (SRS) in the DCF. Since we simultaneously use optical amplification by the two processes, the gain bandwidth is easily expanded over 105 nm by a two‐tone pumping scheme. Using an experimental setup constructed with a hybrid structure of EDF‐DCF‐EDF, we analyzed the spectral behavior of amplified spontaneous emission for pumping powers. We achieved an optical gain of over 20 dB in the wavelength range from 1,500 to 1,600 nm under optimized pumping conditions to make the spectral gain shape flat.