Theoretical study of W-shaped optical fiber with a depression in core center by applying analytical transfer matrix method

Analytical transfer matrix method (ATMM) is a method for calculating the propagation constant in weakly guiding optical fiber. By using ATMM, the optical fiber with a depression in the index profile center and a valley in the cladding layer is analyzed. Compared with Wentzel-Kramers-Brillouin (WKB) method, the simulation result of differential mode delay (DMD) by using ATMM fits well with the experimental results obtained by Takahashi. Based on ATMM, by increasing the depth of central depression in a W-shaped index fiber, the improvement of DMD is also discussed.     

Characteristics of the bandwidth in gain-clamped erbium-doped fiber amplifiers

1.IntYoductionErbium-dopedfiberamplifiers(EDFAs)arepresentlyofgreatinterestinopticalfibercommunicationsystem.Thegainprofiles,thatis,thegainforallwavelengthsofinter-est,areveryimPortantproPertiesofEDFAsinthewavelength-division-multip1exing(WDM)fibersystems['j.Manynumericalandanalyticalmethods(seeforexampleL1jandreferencestherein)canbeusedtoinvestigatethegainprofile8ofEDFAs,buttheyneedcumbersomemeasurementS(forexampIesPectraImeasurementsofEr-dopingabsorWtionandemission,andsoon)andhence…     

前馈PMD补偿实验中从偏振度椭球获得差分群时延的研究

运用偏振度(DOP)椭球法从实验的有限样点数据中获得了差分群时延和偏振主态方向,这为前馈补偿实验提供了最关键的技术因素.在实验中获得了偏振主态方向和DGD,而且当DGD较小时,从实验所获得的DGD值与理论模拟的变化趋势基本一致.结果表明当DGD较小时,可以用偏振度椭球法从实验上得到正确的DGD和偏振主态方向.     

A deeper analysis of the second order polarization mode dispersion in optical communications systems

This article presents a new approach to the combined analysis of the first and second-order polarization mode dispersion (SOPMD) and shows their importance in optical communication systems performance. How it affects the relation between second-order polarization mode dispersion (PMD) and the differential group delay (DGD) in a single mode fiber is discussed. The analysis is based on time or wavelength and temperature variations changing/impacting PMD and DGD measured values. We present long term statistical characteristics of second-order PMD over a PMD emulator, and investigate the correlation between SOPMD, depolarization (DEP) and polarization dependent chromatic dispersion (PCD). Some authors calculate these modes from measurements obtained from the first order polarization mode dispersion, assuming a positive correlation between these effects, but this not the real relationship between them. A new interpretation of SOPMD was used to analyze the problem of the spectral stability in terms of the temperature. Actual techniques for determination SOPMD, consequently DEP and PCD, use the variation in time and/or wavelength. In some studies the results obtained for SOPMD are correlated to first-order PMD (FOPMD). This paper shows, based on measurements, that the correlation between first and second order Polarization Mode Dispersion (PMD) in the case where the last one is a function of the temperature can assume positive or negative values.     

三类偏振模色散模拟器的多阶特性和频率统计相关性分析

对现有三类偏振模色散模拟器：旋转晶体型、偏振控制器型和加热器型模拟器,进行了详尽的相关群时延、高阶偏振模色散的统计分布和频率自相关函数三大统计特性的数值模拟和性能比较.以级联段数作为主要参量的分析结果表明：相关群时延分布的产生准确度,旋转晶体型模拟器略优于偏振控制器型,而加热型模拟器相对最差;在产生精确的高阶偏振模色散分布方面,偏振控制器型模拟器最为优越,加热型模拟器略优于旋转晶体型;而对于产生较低的频率自相关本底水准方面,加热型模拟器则优于偏振控制器型和旋转晶体型.综合而言,偏振控制器型模拟器的性能最为优越;十段左右的偏振控制器型模拟器就可以产生合格的模拟效果,其效果等价于十五段以上旋转晶体型,或二十段以上加热型模拟器.     

光子晶体缺陷模的带宽与品质因子研究

利用光学传输矩阵法研究了结构参量对缺陷态光子晶体的缺陷模带宽和品质因子的影响.研究发现,当缺陷介质层厚度h₀的值较小时,缺陷模的带宽很小且基本保持不变;当h₀较大时,缺陷模的带宽随h₀的增加而快速增加.另外发现,缺陷模的品质因子在某个h₀处取最大值.但是总体上看,h₀较小时的品质因子要远大于h₀较大时的品质因子.此外,缺陷模的品质因子随光子晶体的周期数增加而急剧增加约4.788倍,而带宽则随周期数的增加而急剧减少约4.788倍.当周期数为13时就可以获得10⁹以上的品质因子值和小于10^-9的相对带宽值.     

偏振模色散补偿中的偏振主态与分束器主轴的对准

光纤通信系统的比特率超过10Gb/s或更高时,偏振模色散引起的脉冲信号展宽成为主要障碍.分离光纤线路中的两个偏振模式对于提高偏振模色散补偿的精度和速度有重要意义.讨论了光纤线路中两偏振主态与补偿器中偏振分束器主轴的对准问题,给出了偏振分束器任何一个主轴上光强的表示并推导出相应的电功率信号表示式,建立了电功率与光信号两个模式之间的延迟时间以及偏振主态与分束器主轴相对角度的变化关系.初步实验表明,可以通过偏振控制器或可转动的光纤连接器实现偏振主态与偏振分束器的对准.     

An efficient method for calculation of the MM fiber frequency response in the presence of mode coupling

We present a more efficient and less time consuming method for calculating the mode coupling effects in multimode fibers. Instead of solving the power transfer equation, we solve the system of coupled equations. It is shown that this method is much faster, more accurate and easier to implement. It allows defining the fiber transfer function in the matrix formalism. The convergence of the power transfer equation to our method is investigated.     

Aerosol extinction coefficient profile retrieval in the oxygen A-band considering multiple scattering atmosphere. Test case: SCIAMACHY nadir simulated measurements

A multiple scattering inversion procedure for the aerosol extinction coefficient profile retrieval and error assessment in the oxygen A-band, for passive remote sensing instruments, has been developed. The procedure has been applied to SCIAMACHY nadir simulated measurements to investigate its effectiveness in the troposphere.The inversion procedure consists of a multiple scattering Forward Model, an inversion method and a complete sensitivity and error assessment tool. The Forward Model is based on LIDORT code; the inversion method, the sensitivity study and the complete error assessment are based on Optimal Estimation. The sensitivity and error analysis has been derived to investigate the profile retrieval errors due to the uncertainty of different aerosol optical properties, molecular and surface parameters.The analysis confirms that the profile retrieval accuracy and vertical resolution are strongly dependent on the oxygen A-band spectral resolution. The moderately high SCIAMACHY spectral resolution (0.4 nm in the oxygen A-band) results in distinguishing a maximum of three aerosol layers in troposphere. The SCIAMACHY tropospheric aerosol profile retrieval is shown to be highly sensitive to aerosol optical properties as phase function and single scattering albedo. The sensitivity study reveals an improvement of information content increasing the solar zenith angle and decreasing the surface albedo. As regards the forward model, negligible errors occur as the number of streams exceeds 6.     

反射式全息滤光片的带宽和考虑记录介质吸收后的衍射效率

用重铬酸盐明胶底片可制成反射式全息滤光片,本文导出了这种滤光片的带宽理论公式,在修改的耦合波理论的基础上,导出了与记录全息过程中吸收系数有关的峰值衍射效率公式,由此,提出了对这种滤光片的制造和使用的建议.     

光纤中高斯型伪随机序列码偏振度的理论分析和实验研究

推导了准单色光波情况下高斯脉冲伪随机序列偏振度的简洁数学表达式.理论分析结果表明,偏振度与差分群延迟之间的关系与线路啁啾和光纤色散无关,并且此关系可以由光信号频谱半宽度Δω和分光比γ唯一确定.用10 Gbit/s 7级m序列归零码进行的实验表明:实验结果与理论推导基本一致,从而验证了推导公式的正确性.     

Dispersion Analysis of Birefringent Dielectric Grating Structure for Application in Pressure and Temperature Measurements

In this paper, the dispersion characteristics of a birefringence dielectric planar grating structure for application in pressure and temperature measurements are analyzed by a method, which combines the edge element method with rigorous mode matching approach. Analysis results show that this new anisotropic grating structure offers very high sensitivity for pressure and temperature measurements. Also it is justified that the present method has the advantages of simplicity, accuracy and suitability.     

Revisiting the sodium and calcium matrix effects in inductively coupled plasma optical emission spectrometry. Excitation mechanisms by inelastic collisions

Abstract

The dependence of calcium and sodium matrix effects on the total excitation energy of analyte emission signals was used as a tool for the study of excitation mechanisms in radial view mode inductively coupled plasma optical emission spectroscopy. A total of 95 atomic and 66 ionic emission signals of aluminum, cobalt, chromium, iron, magnesium, manganese, nickel, and silicon in the 3.0–17.59?eV energy range were measured at the non-robust plasma operating conditions to facilitate the matrix effect study. Different matrix effects versus total excitation energy relationships were observed regarding the energy interval. The change of sign from negative to positive of the both matrix effect versus total excitation energy relationship observed around 14?eV, in the 12.06–17.59?eV energy range, is interpreted as experimental evidence of the action of two non-thermic excitation mechanisms: Penning ionization from approximately 12 to 14?eV and charge transfer from 14 to 17?eV. Based on the energy resonance principle and total spin conservation Wigner’s Theorem, possible reactions between excited ionic argon and ground state analyte ions were proposed.     

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在HL-2A单零偏滤器条件下,对由弱场侧沿赤道平面垂直注入的电子回旋寻常波(O-模)的波迹和波的功率沉积剖面进行了分析计算。对近磁轴共振情形,需要确定一个有效的物理尺度以正确获得波功率沉积。单一波束的有效吸收层的厚度可以合理地作为这一物理尺度,从而获得统一的功率沉积公式。对比研究了磁轴偏离赤道面和位于赤道面情况下的波功率沉积剖面。     

The influence of the background interference on the escape of photons in atomic absorption measurements

The influence of the background interference on the escape of photons in the determination of Nickel by atomic absorption analysis for a wide range of concentrations between 10 and in an air-acetylene flame have been investigated. Assuming Doppler, Lorentzian and Voigt line profiles for the resonance lines, the resonance escape factor of the Ni-resonance lines at 2320 and have been calculated with and without the effect of the background, in terms of two main parameters, the optical depth in the line center and the number density of absorbing atoms in the ground state. The effect of the background interference due to the presence of the SO₂-molecular band can cause a change in the escape factors values. The dependence of the escape factor for the Voigt distribution on the damping constant is also discussed.     

Mass measurements of relativistic projectile fragments in the storage ring ESR

Two experimental methods of measuring masses of exotic nuclei in the storage ring ESR are presented. Bismuth and nickel fragments were produced via projectile fragmentation, separated and investigated with the combination of the fragment separator FRS and the ESR: (i) Direct mass measurements of relativistic projectile fragments were performed using Schottky mass spectrometry (SMS), i.e., exotic nuclei were stored and cooled in the ESR. Applying electron cooling, the relative velocity spread of circulating low intensity beams can be reduced below 10⁻⁶. Under this condition a mass resolving power of up to m/Δm=6.5·10⁵ (FWHM) was achieved in a recent measurement. Previously unknown masses of more than 100 neutron-deficient isotopes have been measured in the range of 60≤Z≤84. Using known Q _α values the area of known masses could be extended to more exotic nuclei and to higher proton numbers. The results are compared with mass models and extrapolations of experimental values. In a second experiment with ²⁰⁹Bi projectiles the area of the measured masses was extended to lower proton numbers. Due to various improvements at the ESR the precision of the measurements could be raised. (ii) Exotic nuclei with half-lives shorter than the time needed for SMS (present limit: T _1/2 ≈ 5 sec) can be investigated by time-of-flight measurements whereby the ESR is operated in the isochronous mode. This novel experimental technique has been successfully applied in first measurements with nickel and neon fragments where a mass resolving power of m/Δm=1.5·10⁵ (FWHM) was achieved.     

一种新型的束流剖面探测系统

介绍了一种以微通道板和电阻阳极所构成的位置灵敏探测器为基础、用于兰州重离子加速器束流诊断的新型剩余气体电离束流剖面探测系统.描述了其工作原理、系统结构及初步实验结果,证明利用剩余气体电离束流剖面探测系统进行非拦截束流诊断的方法是可行的.     

Study on some aspects of the “singer's formant” in north indian classical singing

This article deals with a spectrographic analysis of the singer's formant as occurred during singing of the vowels /a/, /i/, and /o/ in North Indian classical vocal music. The resonance balance, center frequency, and band-width are shown as a function of fundamental frequency for eight singers.Two new parameters have been defined viz. asymmetry parameter (A) and spectral energy balance (W). Their variation with fundamental frequency is shown.     

Demonstration of PMD compensation by using a DSP-Based OPMDC prototype in a 43-Gb/s RZ-DQPSK, 1200 km DWDM transmission

This paper reports the DSP-based prototype compensator we have made to compensate the polarization mode dispersion (PMD) in fibers. It was tested in one channel of a 40 × 43-Gb/s DWDM DQPSK system, which is the commercial product line, either in the back-to-back case by using a PMD emulator, or in a 1200-km transmission testbed. The prototype showed a good performance under the tests of fast SOP and PSP rotation, DGD jump variation, and moderate knock on the testbed in a period as long as 12 h.