-1800 ps/(nm.km) chromatic dispersion at 1.55 μm in dualconcentric core fibre

A single-mode optical fibre exhibiting a very high negative chromatic dispersion (1800 ps/(nm.km)) at 1.5 μm is realised and characterised for dispersion compensation applications     

Experimental evaluation of chromatic dispersion distortion inoptical CPFSK transmission systems

Receiver sensitivity degradations due to fiber chromatic dispersion without chromatic dispersion compensation in multigigabit optical continuous-phase frequency-shift-keying (CPFSK) transmission systems are evaluated experimentally and theoretically. Transmission distance limited by the chromatic dispersion of 15 ps/nm/km is estimated to be 130 km at 5 Gb/s and 33 km at 10 Gb/s     

Waveform degradation due to dispersion effects in an optical CPFSKsystem

Waveform degradation due to polarization and chromatic dispersions in a single-mode fiber is calculated for a coherent CPFSK signal. For a single-mode fiber with polarization dispersion of ⩽1 ps, chromatic dispersion almost dominates the system. However, if a fiber has polarization dispersion of more than a few picoseconds and a chromatic dispersion of less than 0.1 ps/km/nm, which can be attained by using a dispersion-shifted fiber and/or by electric dispersion compensation, polarization dispersion will restrict transmission capacity. For instance, polarization dispersion of 5 ps will restrict a bit rate by ~60 Gb/s when chromatic dispersion is fully reduced using a dispersion-shifted fiber or applying electrical equalization     

12300 ps/nm, 2.4 Gb/s nonregenerative optical fiber transmissionexperiment and effect of transmitter phase noise

A nonregenerative optical transmission experiment with a chromatic dispersion of more than 10000 ps/nm is reported. Externally intensity-modulated 2.4 Gb/s optical signals were transmitted over 710 km of nondispersion-shifted optical fiber using ten Er-doped fiber amplifiers with a total net optical gain of 125 dB. Although the total chromatic dispersion amounted to 12300 ps/nm, the power penalty observed was as small as 0.5 dB, and an error floor was not observed. The effect of transmitter phase noise associated with fiber chromatic dispersion was experimentally investigated     

新型光子晶体光纤近零平坦色散的研究

文章作者设计了一种新型的光子晶体光纤(PCF),在纤芯引入了一个小空气孔形成缺陷,并改变第一层空气孔的直径.采用平面波法研究了该PCF的色散特性,结果表明,该光纤能够得到比传统的PCF更低、更平坦的色散曲线;通过优化该光纤的结构参数,可以设计在1 350～2 010 nm波长范围内近于零的平坦色散PCF,其色散变化△D＜0.5 ps/(km·nm),在1 320～2 040 nm波长范围内色散斜率变化△D<,slope>＜0.02 ps/(km·nm<'2>).     

Photonic crystal fiber with novel dispersion properties

Our recent research on designing microstruc-tured fiber with novel dispersion properties is reported in this paper. Two kinds ofphotonic crystal fibers (PCFs) are introduced first. One is the highly nonlinear PCF with broadband nearly zero flatten dispersion. With introducing the germanium-doped (Ge-doped) core into highly non-linear PCF and optimizing the diameters of the first two inner rings of air holes, a new structure of highly non-linear PCF was designed with the nonlinear coefficient up to 47 W-1·km-1 at the wavelength 1.55 μm and nearly zero flattened dispersion of ±0.5 ps/(km·nm) in telecom-munication window (1460-1625nm). Another is the highly negative PCF with a ring of fluorin-doped (F-doped) rods to form its outer ring core while pure silica rods to form its inner core. The peak dispersion - 1064 ps/(km·nm) in 8 nm full width at half maximum (FWHM) wavelength range and -365ps/(km·nm) in 20nm (FWHM) wavelength range can be reached by adjusting the structure parameters. Then, our recent research on the fabrication of PCFs is reported. Effects of draw parameters such as drawing temperature, feed speed, and furnace temperature on the geometry of the final photonic crystal fiber are investigated.     

基于组合包层的微结构光纤的色散特性

为了获得微结构光纤的平坦色散特性,设计了一种圆形排列的微结构光纤,其包层由周期分布的空气孔构成,通过有限元数值分析法对该微结构光纤基模的色散特性进行了数值仿真,研究了色散和纤芯圆孔尺寸以及波长的关系。结果表明:内外空气孔间距和直径对微结构光纤的色散曲线都有影响,但内包层大孔间距和第一圈小空气孔的直径对色散曲线的走向起决定作用。在内圈空气孔直径为3.1μm,其他空气孔直径为1.0μm,内圈空气孔中心间距为5μm,其他空气孔中心间距为4μm时,光纤在1.3μm波长的色散为19.5ps/(nm·km),在1.6μm波长的色散为26.5ps/(nm·km),在1.3～1.6μm波长范围内,其色散值变化范围为7ps/(nm·km)。     

C波段色散补偿光子晶体光纤的研究和设计

设计了一种新颖结构的双层芯色散补偿光子晶体光纤。此光纤在整个C波段具有高负色散特性。通过合理选取双层芯光纤的外层芯层数,同时优化孔间距和空气孔直径,设计的光纤在C波段的色散值在-520ps/(km.nm)和-390ps/(km.nm)之间近似线性变化,残余有效色散系数近似为零,相关色散斜率(RDS)在0.0032nm-1的色散补偿光纤,其RDS值与标准单模光纤匹配,有效模场面积优于常规色散补偿光纤,可以对其长度30倍以上、用于宽带传输的标准单模光纤进行良好的色散和色散斜率补偿。     

Electronic compensation of PMD and chromatic dispersion with an ICin 10 Gbit/s transmission system

A system experiment is reported in which polarisation mode dispersion (PMD) and chromatic dispersion (CD) compensation was achieved using an SiGe IC linear equaliser, with a transmission rate of 100 bit/s over 95 km of standard single-mode fibre (DL=1600 ps/nm). Full equalisation was obtained, with a differential group delay (DGD) of <65 ps and a penalty reduction to 3.4 dB for DGD=100 ps     

Chromatic-dispersion compensator using virtually imaged phasedarray

A new method for chromatic-dispersion compensation is proposed and demonstrated. This method can produce a chromatic dispersion practically in a wide range from -2000 to +2000 ps/nm and can compensate simultaneously for the dispersion of over 60 wavelength channels with 100-GHz spacing in a wavelength-division multiplexed (WDM) system that has a total bandwidth of over 50 nm. This method has further attractive features such as very small polarization-state dependence, mechanically variable chromatic dispersion, and potential for small packaging. It was experimentally confirmed that this method compensated for the chromatic dispersion accumulated through 110 km standard single-mode fiber (SMF) at 1.55-μm wavelength and that 10-Gb/s signal quality was clearly recovered after the 110-km transmission     

A study on the relationship between DWDM transmission performance and chromatic dispersion

In this letter, we numerically study the relationship between 40-Gb/s-based dense wavelength-division-multiplexing (DWDM) transmission performance and chromatic dispersion in two different transmission lines. We show that the optimum chromatic dispersion region for improving the DWDM transmission performance varies with the type of transmission line. We also show that a hybrid transmission line has a greater potential to resist any change in the dispersion slope compensation characteristics than a single fiber transmission line with a dispersion compensation fiber module. Finally, we show that chromatic dispersion of more than 12 ps/nm/km in a hybrid transmission line is optimum for a 40-Gb/s-based DWDM transmission system by taking the design of a dispersion compensating fiber into account.     

Application of a Prechirp Technique to 10-Gb/s Transmission at 1064 nm Through 24 km of Photonic Crystal Fiber

The prechirp effect on 10-Gb/s transmission in the 1000-nm band over photonic crystal fiber (PCF) was investigated both experimentally and theoretically. We performed transmission experiments using a 24-km-long PCF whose optical loss and chromatic dispersion were 0.94 dB/km and$-$20 ps/nm/km at 1064 nm, respectively. We confirmed an improvement in the bit-error-rate performance after the transmission, namely a “negative power penalty” of about$-$0.5 dB. Our experimental result and theoretical estimation revealed that the signal degradation induced by the chromatic dispersion can be effectively suppressed by employing the prechirp technique with a conventional$Z$-cut lithium niobate modulator.     

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。     

Highly accurate long-span chromatic dispersion measurement system by a new phase-shift technique

A highly accurate long span chromatic dispersion measurement system, which is based on a wavelength-division-multiplexing phase-shift technique and utilizes six laser diodes in1.2 sim 1.6 mum spectral region, has been developed. It is intrinsically free from error due to the fiber length variation caused by temperature changes under the measurement. The measurement accuracies of dispersion and Zero-dispersion wavelength are extremely good and within ±0.02 ps/km . nm and ±0.1 nm in 1250 ∼ 1450 nm spectral region in the case of a 10.5-km single-mode fiber measurement. The dynamic range is over 50 dB excluding system theS/Nmargin of 5 dB. Using this system, chromatic dispersion measurements of a 101.9-km pure-silica-core single-mode fiber and a 100.7 km concatenated dispersion-shifted single-mode fiber have been successfully carried out. The measured result has coincided with the arithmetical mean of those of constituent fibers.     

Measurement of chromatic dispersion of long spans of single-mode fibre: a factory and field test method

A simple and accurate method for measuring the chromatic dispersion of long spans of single-mode fibre in the vicinity of the minimum-dispersion wavelength is described. Agreement with Nd-YAG/Raman measurements is better than 0.5 ps/km nm within ±30 nm of ?0. A summary of recent field results is also given.     

A novel chromatic dispersion monitoring method for 400 Gbit/s 256 QAM fiber-optic system based on asynchronous amplitude sampling

A novel chromatic dispersion (CD) monitoring technique based on asynchronous amplitude sampling (AAS) is proposed for a higher modulation format and higher rate system. The dispersion and other impairment factors can be separated with the definition of monitoring parameter M. A 400 Gbit/s 256 quadrature amplitude modulation (QAM) system is built using Optisystem13.0 beta software. Simulations of CD monitoring technique for different bandwidths of sampling Gaussian filter, optical signal to noise ratios (OSNRs) and duty cycles are investigated, and the tolerance is also discussed. Simulation results show that the method can be less affected by noise, and a higher accuracy of 600 ps/(nm.km) can be achieved. The technique supports a wide range of data traffic and enhances operation flexibility of optical networks.     

Measurement accuracy of chromatic dispersion by the modulation phase technique

A simple measuring method for the chromatic dispersion measurement is described. This technique uses group delay measurement by modulation phase of laser diodes with different wavelengths. An experiment showed that this technique is capable of measuring the chromatic dispersion of a 42.3-km single-mode fiber. The accuracy of measurement is discussed in view of fiber length, modulation frequency, and the number of employed laser diodes. The accuracy is improved when a higher modulation frequency is used and a longer fiber is measured since the detected phase fluctuation depends little on the modulation frequency and very little on the fiber length. The estimated measurement error of chromatic dispersion was 0.1 ps/km/nm for a four-laser diode system.     

Low-dispersion fluoride glass single-mode fibres operating in twospectral ranges

Chromatic dispersion characteristics of fluoride glass single-mode fibres are investigated experimentally and theoretically. It is proposed that the quasi-single-mode operation at zero material dispersion wavelength is effective in extending the low dispersive spectral range. It is shown that total chromatic dispersion is suppressed within ±1 ps/km/nm in the two spectral ranges of 1.57-1.71 μm and 2.4-3.35 μm     

Chromatic dispersion characteristics of optical fibre submarine cable under deep sea environmental conditions

First chromatic dispersion characteristics of pure silica-core matched cladding single-mode fibre submarine cable under deep sea environmental conditions are presented. It is confirmed that variations of zero-dispersion wavelength and dispersion at 1.55 mu m wavelength of the cable under hydraulic pressure (0-800 atm), tension (0-6 tons) and temperature change (3-30 degrees C) are less than +or-0.6 nm and +or-0.06 ps/km/nm, respectively.<>     

Long-distance effectiveness of MLSE IMDD receivers

We present numerical evidence that maximum-likelihood sequence estimation (MLSE)-based receivers, assuming ideal implementation, could operate over as much as 11 000 ps/nm of chromatic dispersion (700 km of G.652 fiber), keeping the total penalty with respect to back-to-back within approximately 3 dB. We argue that these results suggest that the penalty of an MLSE-based receiver versus total chromatic dispersion could be bounded to an asymptotic value, provided that enough trellis states are used to properly deal with the channel memory.