Surface plasma waves in silver and gold

The dispersion curves for surface plasma waves (SPW) in Ag have been determined from calculated reflectivity minima as exhibited by attenuated total reflection (ATR spectra) for the prism-air-metal (PAM) configuration and from the direct calculation of the dispersion relation for the same configuration. The dispersion curves for Au have been determined by measuring the ATR spectra for the prism-dielectric-metal (PDM) configuration, by calculating the ATR spectra from published optical constants and from the direct calculation of the despersion relation for the PDM configuration. We have found two general types of solutions from the direct calculation of the dispersion relation for both configurations. The two solutions are the surface or Brewster modes and the virtual modes. The characteristics of both modes are discussed. The effect of electronic damping upon the dispersion curves for Ag which exhibits low electronic damping and Au which exhibits moderate electronic damping is demonstrated. Finally the perturbing effect of the dielectric (referred herein as dielectric shift) upon the displacement of the dispersion curves to higher wave number for the PAM configuration for Ag and for the PDM configuration for Au is shown.     

Interferometric phase-dispersion microscopy

We describe a new scanning microscopy technique, phase-dispersion microscopy (PDM). The technique is based on measuring the phase difference between the fundamental and the second-harmonic light in a novel interferometer. PDM is highly sensitive to subtle refractive-index differences that are due to dispersion (differential optical path sensitivity, 5 nm). We apply PDM to measure minute amounts of DNA in solution and to study biological tissue sections. We demonstrate that PDM performs better than conventional phase-contrast microscopy in imaging dispersive and weakly scattering samples.     

Comparison of the compensation effects of fiber nonlinear impairments with mid-span optical phase conjugation between PDM CO-OFDM system and PDM QPSK system

The compensation effects of fiber nonlinearity in 112 Gb/s polarization division multiplexing(PDM) coherent optical systems by mid-span optical phase conjugation(OPC) based on four wave mixing(FWM) effect are studied. Comparisons of the compensation results between PDM coherent optical-orthogonal frequency division multiplexing(CO-OFDM)system and the single carrier(SC) PDM quadrature phase shift keying(QPSK) system are provided as well. The results demonstrate that nonlinear compensation effect with mid-span OPC in PDM CO-OFDM system is much more obvious than that in SC PDM QPSK system.     

Parity chain and parity chain breaking in the two-level cavity quantum electrodynamics system

We investigate the transitions between energy levels and parity symmetry in an effective two-level polar molecule system strongly coupled with a quantized harmonic oscillator. By the dressed-state perturbation theory,the transition diagrams between the dressed-state energy levels are presented clearly and show that the odd(even) parity symmetry is broken by the permanent dipole moment(PDM) of the polar molecules. By the analytical and numerical methods, we find that when the coupling strength and the PDM increase, the more frequency components are induced by the counter-rotating terms and PDM.     

Analysis of chromatic dispersion effect on coherent optical CPFSK system and performance improvement with the use of combinations of various optical fibers

The performance of a coherent optical continuous-phase frequency shift keying (CPFSK) system is evaluated theoretically including the combined effect of fiber chromatic dispersion, non-zero laser line width and receiver noises. The system limitations imposed by chromatic dispersion and laser phase noise are depicted. The system performance can be improved by shifting the zero-dispersion wavelength to the operating wavelength of the system and this shifting can be achieved efficiently by using a suitable combination of different types of optical fibers. Dispersion shifting characteristics are demonstrated using four kinds of fibers, namely: standard single-mode fiber (SMF), dispersion shifted fiber (DSF), dispersion compensated fiber (DCF) and large core fiber (LCF). The effect of dispersion shifting on the system performance is evaluated in terms of transmission distance and bit rate.     

偏分复用系统信道串扰的理论模型及消除方案

建立了偏分复用(PDM)系统中信道串扰的数学模型,并提出了消除该串扰的方案,即用解复用端一路光信号的射频(RF)功率作为反馈信号以监测光信号在链路中偏振态的变化和在接收端的串扰情况,用粒子群优化(PSO)算法作为逻辑控制单元的算法,控制偏振控制器以消除信道间的串扰。数值仿真了RF功率与信道串扰大小之间的关系,并在2×50Gb/s偏分复用-差分正交移相键控(PDM-DQPSK)传输系统平台上仿真验证了消除串扰方案的效果。结果表明该方案能够大幅降低系统误码率,改善系统性能。     

An improved channel estimation method for a WDM transmission system derived from the CO-OFDM with PDM 64-QAM

In this study, firstly we presented a wavelength division multiplexed (WDM) transmission system derived from the coherent optical orthogonal frequency division multiplexing (CO-OFDM) with polarization division multiplexing (PDM) and 64 order quadrature amplitude modulation (QAM). We then proposed an improved channel estimation method based on discrete Fourier transform for the system to further improve the performance of the WDM transmission system. Under the experimental conditions employed, the principle and the spectral efficiency of the system, including a proposed algorithm to improve its performance (e.g. the robustness of the transmission impairments of the system) were studied. The simulations results demonstrated that our method improved the system efficient significantly. The system signal at 24 Tb/s can achieve a spectral efficiency of 12.5 bit/s/Hz up to a distance of 2000 km.     

Performance of an optical wideband WDM system considering stimulated Raman scattering,fiber attenuation and chromatic dispersion

The performance of an optical wideband wavelength division multiplexed (WDM) communication system is analyzed considering the effects of stimulated Raman scattering, fiber attenuation and chromatic dispersion. Improved models for the Raman gain and the fiber attenuation constant are proposed, which yield better and reliable performance results of the WDM system. Effect of fiber chromatic dispersion is also investigated and it is observed that dispersion can suitably be selected to overcome the limitations imposed by the stimulated Raman scattering phenomenon.     

Comparison of conventional and dense dispersion managed systems for 160 Gb/s transmissions

In this paper, we carry out, by numerical simulations and experiments on recirculating loop, a comparative analysis of the performances of two types of dispersion management techniques for 160 Gb/s transmission systems, which correspond to short-period dispersion maps (dense dispersion management) and long-period dispersion maps (conventional dispersion management), respectively. We show that the dense dispersion management system suffers performance degradation by the effects of polarization mode dispersion (PMD) and fiber splicing losses, in a more dramatic manner than in the system with long-period map. We experimentally find that, at constant PMD, dense dispersion managed system permits to achieve a transmission distance that is twice larger than that obtained with the conventional dispersion management; however, the polarization mode dispersion significantly reduces the gap between the transmission performances of the two types of systems.     

Performance evaluation for 160-Gb/s optical phase conjugation systems considering dispersion mapping and third-order dispersion

The impact of third-order dispersion (TOD) is investigated by numerical simulations in 160-Gb/s singlechannel systems incorporated with dispersion mapping and optical phase conjugation (OPC). System performances using retrun-to-zero (RZ) or carrier-suppressed RZ (CSRZ) modulation format are evaluated on the optimized dispersion map. The results indicate that even though TOD has been fully compensated,the intra-channel nonlinearity induced by local TOD would degrade the system performance in nonlinear regime. The scheme with an optimized dispersion map provides a much higher performance and offers a larger tolerance on a variation of pre-compensation. CSRZ modulation format is more robust due to its tradeoff between tolerances on intra-channel nonlinearity and dispersion.     

光纤非线性效应对10 Gb/s波分复用色散补偿系统的限制

对信道间距为１００ＧＨｚ的８倍１０Ｇｂ／ｓ波分复用色散补偿系统进行了计算机仿真,分析了光纤的色散和自相位调制（ＳＰＭ）、互相位调制（ＸＰＭ）、四波混频（ＦＷＭ）等非线性效应在具有级联光放大器系统中的作用。四种色散补偿方案是：ＳＭＦ（常规单模光纤）＋ＤＣＦ１（色散斜率为正的色散补偿光纤）、ＳＭＦ＋ＤＣＦ２（色散斜率为负的色散补偿光纤）、ＴＷ１（色散为正的非零色散光纤）＋ＴＷ２（色散为负的非零色散光纤     

Effects of pattern dependence on high-power polarization-division-multiplexing applications

High-power polarization-division-multiplexing (PDM) systems or functional modules, such as self-phase-modulation (SPM)-based all-optical regenerators, cross-phase-modulation (XPM)-based wavelength convertors or format convertors, all-optical logical gate, and so on, may suffer from the effects of pattern dependence. Such effects are experimentally investigated using relative time delay variation between bit sequences with orthogonal polarization states in a 2 × 10.65 Gb/s high-power on-off keying (OOK) PDM system. Eye-diagram-based signal-to-noise ratio (SNR) and bandwidth of broadened spectrum are measured and compared. An eye-diagram-based SNR fluctuation of up to 4 dB may occur as the delay changes.     

Localization of s-Wave and Quantum Effective Potential of a Quasi-free Particle with Position-Dependent Mass

The properties of the s-wave for a quasi-free particle with position-dependent mass (PDM) have been discussed in details. Differed from the system with constant mass in which the localization of the s-wave for the free quantum particle around the origin only occurs in two dimensions, the quasi-free particle with PDM can experience attractive forces in D dimensions except D=1 when its mass function satisfies some conditions. The effective mass of a particle varying with its position can induce effective interaction, which may be attractive in some cases. The analytical expressions of the eigenfunctions and the corresponding probability densities for the s-waves of the two- and three-dimensional systems with a special PDM are given, and the existences of localization around the origin for these systems are shown.     

Localization of s-Wave and Quantum Effective Potential of a Quasi-free Particle with Position-Dependent Mass

The properties of the 8-wave for a quasl-free partide with position-dependent mass （PDM） have been discussed in details. Differed from the system with constant mass in which the localization of the s-wave for the free quantum particle around the origin only occurs in two dimensions, the quasi-free particle with PDM can experience attractive forces in D dimensions except D = 1 when its mass function satisfies some conditions. The effective mass of a particle varying with its position can induce effective interaction, which may be attractive in some cases. The analytical expressions of the eigenfunctions and the corresponding probability densities for the 8-waves of the two- and three-dimensional systems with a special PDM are given, and the existences of localization around the origin for these systems are shown.     

Mapping Between Charge-Dyon and Position-Dependent Mass Systems

The primary purpose of this work is to reproduce the scenario composed of a charge-dyon system utilizing position-dependent effective mass (PDM) background in the non-relativistic and in the relativistic regimes. In the non-relativistic case we substitute the exact charge-dyon eigenfunction into PDM Schr?dinger equation, in the Zhu-Kroemer parametrization, and then solve it for the mass distribution considering $M=M(r)$. Analogously, in the relativistic case we study the Klein-Gordon equation for a position-dependent mass, and in this case, we are able to analytically solve the equation for $M=M(r,\theta)$.     

High-speed polarization mode dispersion compensation in a 43-Gb/s RZ-DQPSK transmission system over 1200 km of standard single-mode fibre

This paper reports that the designed optical polarization mode dispersion compensator shows a good performance under the real-time variation of differential group delay, state of polarization and principal state of polarization in a (40 × 43)-Gb/s dense-wavelength-multiplexing, 1200-km enhanced return-to-zero differential-quadrature-phase-shift-keying (RZ-DQPSK) system. The polarization mode dispersion tolerance of the system is improved by 26 ps using the optical polarization mode dispersion compensator. The short and long time stabilities are tested with the bit error ratio recorded.vspace1mm     

On duty cycle selection of RZ optical pulse to optimize the performance of dispersion compensated 10 Gbps single channel optical communication system using dispersion compensating fibers

We present results for duty cycle selection of optical RZ pulse to optimize the performance in 10 Gbps single channel dispersion compensated optical communication system. The system has link length of 240 km with two spans. Each of the spans consists of 120 km standard single mode fiber (SSMF) of 16 ps/nm/km, whose chromatic dispersion is compensated using pre-, post- and symmetrical-dispersion compensation schemes by 24 km dispersion compensating fiber (DCF) of −80 ps/nm/km. The performance of the three compensation schemes is compared by taking 8, 10, 12 and 14 dBm Er-doped fiber amplifier (EDFA) power levels in the link with a duty cycle range (0.1-0.9) of RZ optical pulse. The graphical results obtained show a relationship among the duty cycle, EDFA power and dispersion compensation scheme which predicts the best performing duty cycle case. To optimize performance of the system, we recommend in general, duty cycle less than 0.3 and EDFA power below 8 dB irrespective of compensation scheme. However, with post compensation duty cycle less than 0.7 and EDFA power below 12 dBm give optimum performance. The results conclude that for the high value of duty cycle, post dispersion compensation scheme should be used.     

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.     

基于高阶色散管理和相位共轭技术的色散补偿

相位共轭技术能够同时且高效地补偿二阶色散及非线性效应，且该技术同信号比特率、调制方式无关，是最有前景的色散补偿技术之一。理论分析了在高阶色散作用下，超短高斯脉冲信号在中距相位共轭通信系统中的传输演化特性，数值模拟了在二阶、三阶和四阶色散作用下，飞秒高斯脉冲信号在基于中距相位共轭技术的光纤色散管理链中的动态传输过程。结果表明，相位共轭技术和高阶色散管理相结合，不仅可以补偿和复原包括奇数阶和偶数阶色散在内的全部色散和非线性所引入的信号失真和畸变，而且能够减弱时分复用系统中脉冲之间的相互作用，使得信号在传输一个周期后恢复波形，从而提高了相位共轭系统对失真信号的补偿性能。