Loss of temporal coherence due to fibre chromatic dispersion

Loss of temporal coherence is observed in a two-beam interferometer composed of 1800 m-long fibres with 1.3 ?m and 1.5 ?m zero chromatic dispersion wavelengths. Experimental results fully explain and reflect theoretically predicted ones concerning both the magnitude of degree of coherence and the shape of the coherence curve with respect to the optical path difference.     

Near-field measurements in monomode fibres: determination of chromatic dispersion

A new dispersion measurement for monomode fibres is proposed. It is based on an elaboration of the near-field intensities at different wavelengths. The measurement is considerably simplified and the results are highly accurate.     

New method for measuring the chromatic dispersion of installed single-mode fibers utilizing wavelength division multiplexing techniques

This paper describes a novel method designed to measure the chromatic dispersion of installed single-mode fiber cables. The systems developed utilize the modulation phase/multiple laser diode techniques; however, by the addition of wavelength division multiplexing, the reference laser and fiber was eliminated. Laboratory and field results for measured wavelength ranges of 1200-1330 and 1200-1550 nm are presented.     

Polarization mode dispersion, decorrelation, and diffusion inoptical fibers with randomly varying birefringence

Polarization mode dispersion and the polarization decorrelation and diffusion lengths are calculated in fibers with randomly varying birefringence. Two different physical models in which the birefringence orientation varies arbitrarily are studied and are shown to yield nearly identical results. These models are appropriate for communication fibers. We show that both the length scales for polarization mode dispersion and polarization decorrelation measured with respect to the local axes of birefringence are equal to the fiber autocorrelation length. We also show that the coupled nonlinear Schrodinger equation which describes wave evolution over long length along a communication fiber can be reduced to the Manakov equation. The appropriate averaging length for the linear polarization mode dispersion is just the fiber autocorrelation length but the appropriate averaging length for the nonlinear terms is the diffusion length in the azimuthal direction along the Poincare sphere which can be different, The implications for the nonlinear evolution are discussed     

大气折射和色散对激光传输的影响

由于大气折射和色散效应，当用可见光或红外线瞄准目标而用另一波长的激光对目标进行探测或打击时，瞄准路径和激光传输路径是不一样的，瞄准点和激光束之间存在误差。本文建立了大气层折射模型，并给出了在不同仰角时，用可见光(0．55μm)和红外线(4μm)进行瞄准、用CO2激光器对10km远的目标进行探测或打击，瞄准点和CO2激光束之间的距离大小。     

高双折射低色散光子晶体光纤设计

为了高效传输太赫兹(Terahertz,THz)波并促进太赫兹的实际应用.提出了一种具有高双折射,低色散特性的太赫兹光子晶体光纤(Photonic Crystal Fiber,PCF).利用全矢量有限元法对所提出的PCF 结构进行数值仿真,分析了结构参数与双折射以及色散的关系.仿真结果表明,该光纤在0.9～1.3 TH...     

Impact of chromatic dispersion on DPSK and DQPSK direct-detection optical systems

Chromatic dispersion (CD) limitations for binary and quaternary phase-modulated systems using direct detection receivers are analyzed by numerical simulation, comparing the results with intensity-modulated systems, considering both IMDD (Intensity-Modulation Direct-Detection) and Duobinary formats. Three different receiver structures are assumed and many transmitter and receiver filter bandwidths are spanned, to find out how much CD penalty varies depending on such alternative solutions. Penalty was assessed by means of a very accurate performance estimation semi-analytical technique based on Karhunen-Loève series, which theoretically converges to the exact bit-error rate for direct detection optical systems in the presence of both ase noise and inter-symbol interference. The results show that DQPSK is the most resilient format to CD, as expected, but it is also the less sensitive format to filter bandwidth variations.     

Flicker-noise of electronic equipment: Sources,ways of reduction and application

Formula for calculating intrinsic noises of electronic elements in a wide frequencies range starting from f → 0 is presented here. Ways of reducing intrinsic noises in radio electronic devices in the low frequencies range and examples of using information meaning of flicker noise in practice are described.     

Development of Bi-base high-temperature Pb-free solders with second-phase dispersion: Thermodynamic calculation, microstructure, and interfacial reaction

Bismuth and its alloys are candidates for Pb-free high-temperature solders that can be substituted for conventional Pb-rich Pb−Sn solders (melting point (mp) = 573 – 583 K). However, inferior properties such as brittleness and weak bonding strength should be improved for practical use. To that end, BiCu−X (X=Sb, Sn, and Zn) Pb-free high-temperature solders are proposed. Miscibility gaps in liquid BiCu−X alloys were surveyed using the thermodynamic database ADAMIS (alloy database for micro-solders), and compositions of the BiCu−X solders were designed on the basis of calculation. In-situ composite solders that consist of a Bi-base matrix with fine intermetallic compound (IMC) particles were produced by gas-atomizing and melt-spinning methods. The interfacial reaction between in-situ composite solders and Cu or Ni substrates was investigated. The IMCs at the interface formed a thin, uniform layer, which is an appropriate morphology for a reliable solder joint.     

Measurement of group birefringence and dispersion of polarisation maintaining erbium-doped silica fibre

The group birefringence and chromatic dispersion of a polarisation maintaining bow-tie erbium-doped silica fibre have been measured in the wavelength range 1.2-1.68 mu m by an interferometric measurement technique without any polarisers. The group birefringence is lower than that of a conventional bow-tie fibre and the zero dispersion wavelengths of the two polarisation modes are shifted to 1.613 and 1.630 mu m.<>     

Temperature independence of birefringence and group velocity dispersion in photonic crystal fibres

Experimental results are presented for the dependence of the dispersion and the birefringence of a highly birefringent photonic crystal fibre with temperature. It is shown that, unlike conventional optical fibres, where temperature induces stress regions between the different materials present in their structure, photonic crystal fibres exhibit no dependence with temperature of these optical properties owing to the single material nature of their structures.     

Production of single-mode fibres with negligible intrinsic birefringence and polarisation mode dispersion

Spinning the preform during drawing produces a fibre with a permanent twist. It is shown that such a fibre has negligible polarisation birefringence and rotation. Polarisation mode dispersion is similarly reduced.     

色散监测技术的研究与发展现状

自适应色散补偿技术是高速光纤通信系统中的核心技术之一,而对光信号色散进行动态实时监测是实现自适应色散补偿的关键。系统地总结了色散监测技术的研究与发展现状,对各种动态色散监测技术的机制、特点及其实现进行了分析比较,并重点介绍了全光色散监测技术和基于数字相干检测的色散监测技术,探讨了其未来的发展方向。     

Effects of dispersion and birefringence on the performance ofquantum well mode converters

The device characteristics of GaAs multiple quantum well (MQW) polarization modulators, designed for operation at wavelengths of 865 and 870 nm, respectively, are investigated and shown to depend strongly on the dispersive and anisotropic optical properties of the quantum well medium. Results indicate that the observed decrease in spectral bandwidth and conversion efficiency at wavelengths detuned from the excitonic bandgap by ~250 Å can be accounted for, theoretically, if electroabsorptive loss terms are included in the coupled-mode analysis of polarization conversion in MQW waveguides. Device design considerations and applications of MQW polarization modulators to integrated optic filtering, wavelength division multiplexing/demultiplexing, and the frequency tuning of semiconductor lasers are presented     

Evaluation on system outage probability due to temperature variation and statistically distributed chromatic dispersion of optical fiber

This paper discusses the evaluation of the system outage probability caused by the temperature variation and statistically distributed chromatic dispersion of optical fiber in a high-speed (>40 Gb/s) optical network. This was to identify when the tunable dispersion compensator should be used at every channel.     

Measurement of nonlinear and chromatic dispersion parameters of optical fibers using modulation instability

We present a simple method for the measurement of Kerr, second- and third-order dispersion coefficients in optical fibers using power and dispersion dependences of modulation instability near the zero-dispersion wavelength. We also complete the analysis by the accurate determination of the zero-dispersion wavelength of the fiber using the phase-matched four wave mixing process which occurs near this specific wavelength.     

光纤中的色散和非线性效应对混沌同步的影响

基于描述光反馈半导体激光器的动力学以及信号在光纤信道中传输的理论,研究了光纤中色散和非线性效应对混沌信号传输以及发射和接收激光器的混沌同步特性的影响,目的是为远程光纤混沌保密通信提供理论指导。数值模拟结果表明:光纤非线性效应只影响信号的位相,不会影响混沌信号的强度;光纤色散将使混沌信号发生严重变形,影响混沌系统的同步性能:通过在接收器的前端放置放大器以补偿光纤的损耗,信号经过200km的色散位移光纤传输后,发射和接收激光器输出混沌信号的关联系数仍可达到0.99,即系统可达到很好的同步性能。     

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.     

Interferometric measurements of chromatic and polarisation mode dispersion in highly birefringent single-mode fibres

Interferometric measurements on highly birefringent single-mode fibres have been performed. The group delay spectrum of each polarisation mode is independently measured over the whole 1.0?1.73?m spectral range. The polarisation mode dispersion is obtained by direct subtraction of the group delay spectra.     

Annealing of linear birefringence in single-mode fiber coils:application to optical fiber current sensors

Annealing procedures that greatly reduce linear birefringence in single-mode fiber coils are described. These procedures have been successfully applied to coils ranging from 5 mm to 10 cm in diameter and up to 200 or more turns. They involve temperature cycles that last 3-4 days and reach maximum temperatures of about 850°C. The residual birefringence and induced loss, are minimized by proper selection of fiber. The primary application of these coils is optical fiber current sensors, where they yield small sensors that are more stable than those achieved by other techniques. A current sensor with a temperature stability of +8.4×10^-5/K over the range from -75 to +145°C has been demonstrated. This is approximately 20% greater than the temperature dependence of the Verdet constant. Packaging degrades the stability, but a packaged sensor coil with a temperature stability of about +1.6+10^-4/K over the range from -20 to +120°C has also been demonstrated