Extenuation of phase shift influenced nonlinear impairments in fiber optics network

Antecedentes: la información en un canal de fibra óptica sufre distorsiones debido a la aparición de efectos lineales y no lineales, restringiendo la velocidad de transmisión. En este documento se analiza el error no lineal denominado automodulación de fase (SPM),el cual genera un desfase en los pulsos trasmitidos, ocasionando errores de bits en la comunicación. Objetivo: el proyecto está orientado a evaluar el comportamiento del error no lineal SPM en una comunicación monocanal de fibra óptica utilizando Matlab. Métodos: su desarrollo parte del modelado matemático del error SPM, para ser codificado en Matlab y evaluar su desempeño en el canal para condiciones específicas. Para realizar las simulaciones se implementó un canal de comunicaciones en fibra óptica, teniendo en cuenta los parámetros que rigen las redes XGPON o 10GPON que son la siguiente generación de Red Óptica Pasiva con Capacidad de Gigabit (GPON). Para simular el canal de fibra óptica se definieron las distancias de 20, 40 y 60 km, y las potencias de 4, 10 y 20 mW, con velocidades de transmisión de 10 Gbps, en las longitudes de onda de 1550 y 1310 nm, usando la modulación QPSK. Los parámetros para desarrollar la simulación consideraron las recomendaciones de la Unión Internacional de Telecomunicaciones (ITU). Resultados: mediante un análisis gráfico se identificaron los parámetros que afectan el error SPM, como la potencia, el área efectiva, la distancia y el tipo de fibra, entre otros. Conclusión: el error SPM por sí solo no es perjudicial para las redes XGPON en la modulación QPSK, considerando que el máximo desfase obtenido en el proyecto fue de 28.8°, siempre y cuando se tengan en cuenta la potencia, la distancia y los tipos de fibra, de acuerdo con las recomendaciones de la ITU (G652, G987, G691 y G957). Palabras clave: Automodulación de fase, fibra óptica monomodo estándar, modulación por desplazamiento cuaternario de fase, red óptica pasiva con capacidad de gigabit.AbstractBackground: the information transmitted by optical fiber channels is distorted due to the appearance of linear and nonlinear effects, which restrict the transmission rate, this paper analyzes the nonlinear error selfphase modulation (SPM) Objective: the project aims to evaluate the behavior of nonlinear error SPM in a single channel fiber optic communication using Matlab. Methods: development of the mathematical modeling of error SPM to be coded in Matlab and evaluate their performance in the channel for specific conditions. To perform simulations a communications channel is implemented in fiber optics taking into account the parameters governing XGPON or 10GPON networks or which are the next generation of Gigabit Passive Optical Network (GPON). To perform simulations three distances 20, 40 and 60 km, and three power values of 4, 10 and 20 mW were defined, with transmission speeds of 10 Gbps wavelengths 1550 and 1310 nm, respectively; using QPSK modulation. The parameters to simulate were defined taking into account the recommendations of the International Telecommunication Union (ITU). Results: using a graphical analysis we identified the parameters that affect the error SPM, such as potency, the effective area, the distance, the fiber type, among others. Conclusion: the error SPM alone is not harmful to the GPON networks in QPSK modulation, considering that the maximum phase shift obtained in the project was 28.8°, provided that the power, the distance and the types of fiber are taken into account according to the recommendations of the ITU (G652, G987, G691 y G957).Keywords: Gigabit passive optical network, quaternary phase shift keying, self phase modulation, standar singlemode fiber.

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Object Wave Determination by Single-Sideband Methods

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071776 ◽

1973 ◽

Vol 31 ◽

pp. 266-267

Author(s):

Kenneth H. Downing ◽

Benjamin M. Siegel

Keyword(s):

Phase Shift ◽

Carbon Films ◽

Object Wave ◽

Electron Wave ◽

Phase Object ◽

Heavy Atoms ◽

Single Sideband ◽

Thin Carbon ◽

Additional Phase Shift ◽

Additional Phase

Under the “weak phase object” approximation, the component of the electron wave scattered by an object is phase shifted by π/2 with respect to the unscattered component. This phase shift has been confirmed for thin carbon films by many experiments dealing with image contrast and the contrast transfer theory. There is also an additional phase shift which is a function of the atomic number of the scattering atom. This shift is negligible for light atoms such as carbon, but becomes significant for heavy atoms as used for stains for biological specimens. The light elements are imaged as phase objects, while those atoms scattering with a larger phase shift may be imaged as amplitude objects. There is a great deal of interest in determining the complete object wave, i.e., both the phase and amplitude components of the electron wave leaving the object.

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A Many-Beam Technique for Enhanced Resolution of Partial Dislocations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096485 ◽

1972 ◽

Vol 30 ◽

pp. 646-647

Author(s):

J. M. Oblak ◽

B. H. Kear

Keyword(s):

Phase Shift ◽

Field Method ◽

Dark Field ◽

Bright Field ◽

Field Technique ◽

Weak Beam ◽

Partial Dislocations ◽

Enhanced Resolution ◽

Nickel Base ◽

Beam Technique

The “weak-beam” and systematic many-beam techniques are the currently available methods for resolution of closely spaced dislocations or other inhomogeneities imaged through strain contrast. The former is a dark field technique and image intensities are usually very weak. The latter is a bright field technique, but generally use of a high voltage instrument is required. In what follows a bright field method for obtaining enhanced resolution of partial dislocations at 100 KV accelerating potential will be described.A brief discussion of an application will first be given. A study of intermediate temperature creep processes in commercial nickel-base alloys strengthened by the Ll2 Ni3 Al γ precipitate has suggested that partial dislocations such as those labelled 1 and 2 in Fig. 1(a) are in reality composed of two closely spaced a/6 <112> Shockley partials. Stacking fault contrast, when present, tends to obscure resolution of the partials; thus, conditions for resolution must be chosen such that the phase shift at the fault is 0 or a multiple of 2π.

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Designing high-resolution slow scan CCD-based TEM camera systems

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012936x ◽

1992 ◽

Vol 50 (2) ◽

pp. 946-947

Author(s):

James F. Mancuso ◽

William B. Maxwell ◽

Russell E. Camp ◽

Mark H. Ellisman

Keyword(s):

Fiber Optics ◽

Ccd Camera ◽

High Energy ◽

Phosphor Layer ◽

X Ray ◽

Light Production ◽

Camera Systems ◽

X Ray Imaging ◽

Electron Image ◽

Scintillating Fiber

The imaging requirements for 1000 line CCD camera systems include resolution, sensitivity, and field of view. In electronic camera systems these characteristics are determined primarily by the performance of the electro-optic interface. This component converts the electron image into a light image which is ultimately received by a camera sensor.Light production in the interface occurs when high energy electrons strike a phosphor or scintillator. Resolution is limited by electron scattering and absorption. For a constant resolution, more energy deposition occurs in denser phosphors (Figure 1). In this respect, high density x-ray phosphors such as Gd2O2S are better than ZnS based cathode ray tube phosphors. Scintillating fiber optics can be used instead of a discrete phosphor layer. The resolution of scintillating fiber optics that are used in x-ray imaging exceed 20 1p/mm and can be made very large. An example of a digital TEM image using a scintillating fiber optic plate is shown in Figure 2.

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Observation of surface morphology by reflection electron holography

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154652 ◽

1989 ◽

Vol 47 ◽

pp. 536-537

Author(s):

N. Osakabe ◽

J. Endo ◽

T. Matsuda ◽

A. Tonomura

Keyword(s):

Phase Shift ◽

Surface Morphology ◽

High Sensitivity ◽

High Energy ◽

Path Difference ◽

Transmission Mode ◽

Electron Holography ◽

Dynamical Process ◽

High Vertical Resolution ◽

Amplification Technique

Progress in microscopy such as STM and TEM-TED has revealed surface structures in atomic dimension. REM has been used for the observation of surface dynamical process and surface morphology. Recently developed reflection electron holography, which employes REM optics to measure the phase shift of reflected electron, has been proved to be effective for the observation of surface morphology in high vertical resolution ≃ 0.01 Å.The key to the high sensitivity of the method is best shown by comparing the phase shift generation by surface topography with that in transmission mode. Difference in refractive index between vacuum and material Vo/2E≃10-4 owes the phase shift in transmission mode as shownn Fig. 1( a). While geometrical path difference is created in reflection mode( Fig. 1(b) ), which is measured interferometrically using high energy electron beam of wavelength ≃0.01 Å. Together with the phase amplification technique , the vertivcal resolution is expected to be ≤0.01 Å in an ideal case.

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