A method for determining errors of a static fiber-optic gyrocompass

The influence of intrinsic noise and signal drift on the accuracy of a static fiber-optic gyrocompass (FOG) is analyzed theoretically, and a method is proposed to determine the errors of the gyrocompass experimentally. From this it is possible to choose an optimum algorithm for measuring the FOG signal and calculating the direction angle with respect to north. Real measurements of the accuracy of an operating gyrocompass yield errors of order 1° (rms). Zh. Tekh. Fiz. 67, 110–113 (September 1997)     

Error statistics in a high-rate communication line with bit-density optimization

Direct effective numerical simulation is used to determine the tails of probability density functions of marks and spaces and the error statistics in the optical communication line based on a conventional single-mode fiber and a dispersion-compensation fiber with a reduced density of marks in the original bit sequence. Simple analytical approximations for the tails of the probability density function are derived to determine the number of errors in the line with a relatively high accuracy.     

Binary phase gratings for couplers used in fiber-optic communications

Abstract

Star couplers and bidirectional couplers for use in fiber optic networks have been constructed using binary phase transmission gratings. The principles of operation and the performance of these devices are discussed. Experimental results are shown which agree with the theoretical predictions to an accuracy of 0.5 dB.     

Binary phase gratings for couplers used in fiber-optic communications

Star couplers and bidirectional couplers for use in fiber optic networks have been constructed using binary phase transmission gratings. The principles of operation and the performance of these devices are discussed. Experimental results are shown which agree with the theoretical predictions to an accuracy of 0.5 dB.     

Old mathematical errors in statistical physics

In this paper, we discuss the following questions of quantum statistics: (1) the absence of Bose condensate in ideal Bose gas in the two-dimensional and one-dimensional case; (2) the concentration of the Bose condensate in an ideal Bose gas at the lowest level of the spectrum of the Schrödinger operator. In classical statistics, we discuss the discrepancy between the notion of Boltzman-Maxwell ideal gas with the notion of saturated vapor. The appearance of clusters requires the complete revision of the Clayperon equation as an equation depending on the number of degrees of freedom. For the new ideal gas and the ideal virtual liquid, we describe the phase transition of the first kind by specifying the concept of negative pressure for ideal virtual liquids.     

The effect of random errors on a large statistical energy analysis model

The framework of analysis known as Statistical Energy Analysis has many important applications particularly in systems where detailed information is not available. As a result of the approximations made, to simplify the calculations, random error can be introduced into the SEA model. For large systems this gives rise to uncertainty in the energy levels. It is shown that the effect of these errors on the model depends on the “shape” of the model. A compact model dominated by short paths is less affected than a model controlled by long paths. In either case the ratio of the average error in the resultant energy level to the average error in the coupling loss factor decreases as the errors increase. This means that large models may be used with confidence even when based on data that is known to be approximate.     

Influence of statistical experimental errors on amplitude correlations in resonance spectroscopy

Measurements taken at Triangle Universities on a running sequence of 53d-wave resonances in⁴⁵Sc strongly suggest that the reduced partial width amplitudes have a probability distribution which is not a multivariate Gaussian. We investigate whether this result could be caused by experimental statistical errors and find strong indications that this might indeed be the case.     

On systematic errors in spectral line parameters retrieved with the Voigt line profile

Systematic errors inherent in the Voigt line profile are analyzed. Molecular spectrum processing with the Voigt profile is shown to underestimate line intensities by 1–4%, with the errors in line positions being 0.0005 cm^?1 and the decrease in pressure broadening coefficients varying from 5% to 55%.     

基于改进的统计信道模型与多天线系统性能分析

为提高电磁信号的到达角度以及多普勒效应等信道参数估计的准确性,在散射体非均匀分布下引入了散射概率和有效散射体两个物理概念,提出一种合理的改进型空间信道模型,该模型能准确地描述宏小区(macrocell)和微小区(microcell)等各种移动通信环境下的重要空时信道参数,并应用于多入多出系统(multiple input multiple output,MIMO)信道性能仿真中.数值仿真结果与早期多径衰落信道模型对比,表明本模型的信道参数估计结果符合理论和经验,拓展了空间统计信道模型的研究和应用,对评估多天线MIMO系统空时处理算法和仿真无线通信系统提供有力的工具.     

Mutual alignment errors analysis based on wavelet due to antenna deformations in inter-satellite laser communications

Wavelet analysis is employed in the paper to model diversified optical antenna deformations in inter-satellite laser communications. Mutual alignment errors, which comprise pointing and tracking errors, caused by the deformations are investigated with the model. Theoretical and numerical analysis show that both errors increase with the dilation factor of the model. Tracking error increases monotonously with the shift factor of the model, while pointing error increases first, and then decreases. When the deformation can be well approximated to a constant, both errors fluctuate periodically with the coefficient of the model. Otherwise, there is no obvious regularity for both errors with the increase of the coefficient. A reference for the machining precision of optical antennas is presented, and a method to reduce the effect of deformations is recommended. It is hoped that the study can contribute to improve the performance of inter-satellite laser communication systems.     

Analyzing statistical errors for measurements of Brillouin scattering by the edge technique

The signal estimate and statistical uncertainty in the measurements of Brillouin shift by the edge technique are analyzed in detail. A signal to noise parameter factor is introduced and is used to discuss the statistical uncertainty in the measurements. The effect of signal averaging and the effect due to background noise are analyzed. Some helpful conclusions are predicted. PACS 42.68.Wt; 42.79.Qx; 78.35.+c     

有效线导纳的仿真研究

利用有效导纳复功率流法研究了无限平板线激励下的功率传递规律,得出了线激励下的有效线导纳的理论公式,并对有效线导纳的功率传递特性进行了仿真研究。比较了有效线导纳理论公式和数值估计公式的计算结果,得到了数值估计公式的适用范围。然后研究了梁线激励作用下的功率传递特,并且对平板和梁上的功率传递规律进行了比较,结果为平板线激励的相对传递功率要略大于梁的相对传递功率。表明有效线导纳的理论公式在研究结构的功率传递上的灵活性和适用性。     

Mesoscale plastic flow instability in a solid under high-rate deformation

Here we consider high-rate deformation in solids in the context of a nonlocal transport theory, present a dynamic stress-strain diagram with elastic and plastic portions defined from a single standpoint, determine the conditions for pulse stress accumulation, and propose a mathematical model of momentum and energy exchange between scales and an instability criterion for transient plastic flow under shock loading. Phe instability criterion for high-rate deformation is verified by the example of shock loading of high-strength 30CrNi4Mo steel.     

Comparison of the errors in determining the weak absorption line parameters by a spectrophotometric and opticoacoustic method

A comparative analysis is performed of the errors in measuring the weak absorption line parameters by spectrophotometric and opticoacoustic methods in the linear and nonlinear absorption domains. Conditions are determined for the best utilization of each of the methods to solve spectroscopy problems of the atmosphere.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 44–48, August, 1987.     

Study of a fiber-optic LAN with a distributed controller

In this paper the performance of a fiber-optic LAN with spread spectrum multiplexing is discussed from the viewpoint of transmission parameters. Two architectures are considered. The first concerns a structure with cascade-connected Y-type fiber-optic couplers. The second concerns an architecture with cascade-connected active optoelectronic repeater-coupler (ORCA) devices.     

Characterisation of instrumental line shape distortions due to path difference dependent phase errors in a Fourier transform spectrometer

In Fourier transform spectroscopy, path difference dependent misalignments, such as those due to imperfect mechanical movement of the scanning mirror, can be modelled as path difference dependent apodisation and phase errors. The theoretical model that relates the mirror drive characteristics to the path difference dependent error is used to verify the consistency of the optical instrument line shape with the measurements of the mechanical drive quality. This procedure can be used as a diagnostic and qualification tool.     

Multiplexing of fiber-optic acoustic sensors in a Michelson interferometer configuration

A new multiplexing method demonstrating the separation of two series of geometrically arranged fiber-optic distributed sensors in a Michelson interferometer (MI) configuration has been developed. This method can acquire data from two sensors, then propagate the data into one channel, and finally separate the data by determining their working point, which is essential for some remote measurements. The working point of one sensor was deflected from the normal MI by introduction of two reference arms. The deflection was extracted electrically and employed to label the sensor. Verification with commercial piezoelectric transducers proves the efficiency of the method.