Optimization Of Optical Systems Research Articles

光学相干层析系统的信噪比分析及优化

光学相干层析系统的信噪比分析及优化

Symmetrized Split-Step Fourier Scheme to Control Global Simulation Accuracy in Fiber-Optic Communication Systems

Analytical expressions involving both system parameters and step-size are proposed to represent the local simulation error for the symmetrized split-step Fourier (SSSF) simulation method. This analytical expression can be used for a step-size selection rule to achieve comparable local simulation accuracy for SSSF simulations. This can lead to computational savings since there is no waste of computation in each simulation step. Furthermore, based on the local error expression, scaling rules are derived to achieve comparable global simulation accuracy for wide ranges of key system parameter values. This is significant in enhancing the computational efficiency in optical fiber communication system design and optimization. Extensive validation tests were performed to explore the application range of the proposed step-size selection and scaling rules. The desired global accuracy can be achieved with the use of our local error expression and scaling rules by only a couple of test trial simulation runs for a variety of practical applications.

Optical study on the vision correction and supernormal vision based on the wave-front aberrations of human eye

In this paper we present the recent research results in the field of vision correction and supernormal vision according to the actual measurements of the wave-front aberrations and the corneal surface topography, the clinical detection of the visual function and the laser corneal refractive surgery, and the optimization of the optical system. These include the features of the aberrations of human eye with different pupil sizes, different fields of view and temporal accommodation, the influence of the polychromatic illumination of the visible wavelength on the supernormal vision, and the effect of the existing laser corneal refractive surgery on the wave-front aberrations of the eye. It is shown that the wave-front aberration of human eye is of temporal variation and of synthesis with multi impact factors. To achieve supernormal vision, an optimum engineering data for the customized laser corneal surgery should be firstly acquired, which may involve the dynamic free-form optical surface. Although the myopia can be corrected by the laser in situ keratomileusis (LASIK) in a certain degree, it brings about negative effects under scotopic conditions.

Optics of oblique meridional and nonmeridional rays of a conicoid

Based on the exact expression for the angular eikonal of an axisymmetric conicoid (a surface formed by revolution of a second-order curve, or conic) the expressions for the Gaussian optics of oblique meridional rays are obtained, which differ from the well-known Gullstrand-Young invariants for a sphere by a set of independent arguments and contain explicitly the parameters of an optical system. The collinear properties of an optical surface with oblique meridional beams are studied. The theory of astigmatism is extended to the case of oblique nonmeridional rays, which makes it possible to construct and analyze in the first approximation the focal surfaces of an actual wide beam of rays. The theory is tested using the example of optimization of an aplanatic lens for the case of an off-axis point of an object. Based on the exact expression for the angular eikonal, definitions of integral aberrations are given. It is proposed to use the method developed in optimization of optical systems.

EUROMET Project 666, EUROMET-PR.S1 Final Report: Intercomparison of chromatic dispersion reference fibres

The calibration of the chromatic dispersion properties of single-mode fibres is of critical importance for a proper optimization of optical fibre communication systems. Although extensive analyses of the commonly used calibration techniques were already performed by some NMIs, no large scale interlaboratory comparisons that could be used as a basis for the MRA existed at this time. The aim of this project was to perform a comparison of chromatic dispersion measurements that were carried out on four of the most commonly used fibre types, namely G652, G653, G655-TeraLight and G655-Leaf. This intercomparison was also registered as a supplementary comparison (Euromet-PR-S1) and will serve as a basis for the review of the CMC entries on chromatic dispersion.This intercomparison addressed the calibration of the three relevant quantities, namely the chromatic dispersion, the zero dispersion wavelength and the dispersion slope. All laboratories used quite similar equipment, but applied very different measurement strategies and data processing techniques. Very good agreement was found between the results provided by most of the participants. One laboratory obtained results with more significant deviations, probably due to a problem in its measurement setup. The results of this laboratory have been analyzed in this report, but have not been used for the determination of the mean value of the reported quantities.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by EUROMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Optimization of Brillouin optical correlation domain analysis system based on intensity modulation scheme

We report a novel method to enhance the performance of Brillouin optical correlation domain analysis system based on the intensity modulation of light source. The suppression and the modification of the background noise in Brillouin gain spectrum is experimentally demonstrated with different intensity modulation schemes. In an optimum configuration, the signal to noise ratio is improved more than 40%, which extends the measurable strain limit and leads to the substantial increase of measurement range.

An SSF scheme to achieve comparable global simulation accuracy in WDM systems

An analytical expression involving both system parameters and step size is proposed to represent the local simulation error for the split-step Fourier simulation. Based on this result, scaling rules are derived to obtain comparable global accuracy for different system parameters. This is significant in enhancing computational efficiency in optical fiber communication system design and optimization.

Numerical simulation of nonuniformly time-sampled pulse propagation in nonlinear fiber

Numerical simulation of pulse propagation in nonlinear optical fiber based on nonlinear Schrodinger equation plays a significant role in the design, analysis, and optimization of optical communication systems. Unconditionally stable operator-splitting techniques such as the split-step Fourier method or the split-step wavelet method have been successfully used for numerical simulation of uniformly time-sampled pulses along nonlinear optical fibers. Even though uniform time sampling is widely used in optical communication systems simulation, nonuniform time sampling is better or even desired for certain applications. For example, a sampling strategy that uses denser sampling points in regions where the signal changes rapidly and sparse sampling in regions where the signal change is gradual would result in a better replica of the signal. In this paper, we report a novel method that extends the standard operator-splitting techniques to handle nonuniformly sampled optical pulse profiles in the time domain. The proposed method relies on using cubic (or higher order) B-splines as a basis set for representing optical pulses in the time domain. We show that resulting operator matrices are banded and sparse due to the compact support of B-splines. Moreover, we use an algorithm based on Krylov subspace to exploit the sparsity of matrices for calculating matrix exponential operators. We present a comprehensive set of analytical and numerical simulation results to demonstrate the validity and accuracy of the proposed method.

Finding new local minima by switching merit functions in optical system optimization

A strategy to escape from poor local minima by switching merit functions during local optimization is discussed. As a switching partner, we define a new auxiliary merit function, which also tends to zero for ideal systems, but differs significantly from traditional merit functions. The examples include high-dimensional optimization problems. © 2005 Society of Photo-Optical Instrumentation Engineers.

Networks of local minima in optical system optimization.

We discuss a surprising new feature of the merit function landscape in optical system design. When certain conditions are satisfied, the local minima form a network in which all nodes are connected. Each link between two neighboring minima contains a saddle point with a Morse index of 1. For a simple global optimization search (the symmetric Cooke triplet), the network of the corresponding set of local minima is presented.

New approaches for the validation of transfer maps using remainder-enhanced differential algebra

High-order transfer maps of particle systems play an important role in the design and optimization of particle optical systems, both for satisfying the basic design needs as well as for the correction of aberrations and non-linear effects, and the differential algebraic (DA) method has proved useful for this problem. Since the high-order maps represent an approximation of the motion, in particular in strongly nonlinear cases in which convergence of the maps may be slow, it is important to know the quality of the approximation. Recent work has shown that it is in principle possible to not only propagate the conventional differential algebraic high-order objects, but also adjoint remainder terms that rigorously account for any errors made by the approximation by the Taylor expansion over the domain of interest. In this paper we describe various recent enhancements of the original method of computations with remainder bounds that allow the control of the errors made both by the integrator scheme and any possible inaccuracy of the description of the system. Using suitable extensions of the DA and Taylor model operators used in the Schauder fixed point theorem formulation of the ODE problem leads to a very transparent approach for the calculation of enclosures for the intergration errors. Under the presence of a scheme for effective treatment of sparsity in the DA vectors, such as the method available in the code COSY INFINITY, the additional resources necessary for this algorithm are very modest.

Optimization of urban optical wireless communication systems

Urban optical wireless communication systems are considered a "last mile" technology. An optical wireless communication system uses the atmosphere as a propagation medium. In order to provide line-of-sight (LOS), the transceivers are placed on high-rise buildings. However, dynamic wind loads, thermal expansion, and weak earthquakes cause buildings to sway. These sways require the designer to increase the transmitter beam divergence angle so as to maintain LOS between the transmitter and the receiver. It is clear that an overly wide divergence angle increases the required laser power, and, as a result, terminal cost and complexity increase. On the other hand, an overly narrow beam divergence angle may result in cutoff in communication when there is building sway. In this paper, we derive a mathematical model to minimize transmitter power and optimize transmitter gain (divergence angle) as a function of the building-sway statistics, the communication system parameters, and the required bit-error probability (BEP). Reduction in laser power could improve overall system performances and cost. For example, for BEP of 10/sup -9/, we can attain at least a 4-dB reduction of the required transmitter power in comparison to a system with both half and twice the optimum beam divergence angle.

Optimization of a particle optical system in a mutilprocessor environment

In the design of a charged particle optical system, many geometrical and electric parameters have to be optimized to improve the performance characteristics. In every optimization cycle, the electromagnetic field and particle trajectories have to be calculated. Therefore, the optimization of a charged particle optical system is limited by the computer resources seriously. Apart from this, numerical errors of calculation may also influence the convergence of merit function. This article studies how to improve the optimization of charged particle optical systems. A new method is used to determine the gradient matrix. With this method, the accuracy of the Jacobian matrix can be improved. In this paper, the charged particle optical system is optimized with a Message Passing Interface (MPI). The electromagnetic field, particle trajectories and gradients of optimization variables are calculated on networks of workstations. Therefore, the speed of optimization has been increased largely. It is possible to design a complicated charged particle optical system with optimum quality on a MPI environment. Finally, an electron gun for a cathode ray tube has been optimized on a MPI environment to verify the method proposed in this paper.

Optimum optical system for generating interference signals in quadrature using polarization method

A technique is described for designing optical systems for generating interference signals in quadrature. This technique, which op- timizes the amplitude and quadrature of the interference signals, is then used to optimize a phase quadrature interference system with minimal optical components and optical efficiency greater than standard systems. © 2001 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1346581)

Computer simulation tools for the design and optimization of optical disk systems

This paper describes the development and application of software models for the design and optimization of the record, readout and data recovery processes in all commonly used optical disk storage formats. A detailed design example for CAD MSR/MAMMOS system is described. Written bits, readout waveforms, and the performance of PRML for this new format are presented.

Multi-criteria approach in optimization of the optical schemes for magnet mass analyzers

Abstract The multi-criteria optimization – the approach relatively new for optimization of the charged particle optical systems – is considered. As compared with traditional one-criterial optimization it tries to take into account the full set of the criteria instead of the weighted sum of individual criteria specific to the considered system. It appears that quite often it enables to get more and new information about the system. The description of the approach and of the algorithm used to perform the multi-criteria optimization is combined with practical examples of mass analyzers optimized using this method.

Nonlinear programming and scientific computing visualization in the optimization design of electron optical system

Abstract In part I of this paper, five different nonlinear programming methods, improved Powell method, axis directional search method with fixed step, Hook–Jeeves method, axis directional search method with variable step and Rosenbrock method, are discussed for the optimization design of electron optical systems. Major aspects of these techniques in their applications are systematically studied, which include convergence rate, optimal objective function value and global convergence. The calculation results indicate that Rosenbrock method should be recommended in electron optical system optimization. In part II of this paper, an efficient method, reverse-match interpolation method, is presented for the visualized optimization design of electron optical systems, which is a new development of CAD in electron optics. This method can produce the density distribution of electron beam from electron trajectories worked out in the optimization search process. It makes real-time control system possible.

Fast image-quality-based optimization of optical systems

The performance is reported of new optimization software that maximizes the relative modulation transfer function (MTF) by minimizing the merit function (1 minus the approximate relative MTF). Contrary to the predictions of earlier studies, this merit function, whose only variable part is the variance of the wave aberration difference function, is shown to be effective for both poorly and well-corrected systems. In addition, the new software is significantly faster than our in-house software for the direct optimization of the actual MTF.

Communication systems interactive software (comsis): modeling of components and its application to the simulation of optical communication systems

comsis, which stands for communication systems interactive software, is a computer-aided-design tool based on a time approach. It allows the design, analysis, and performance optimization of optical transmission systems by use of various optical devices. comsis allows scalar or vectorial simulations, depending on whether the polarization is taken into account. An overview concerning the optical component models is given. A new model of an erbium-doped fiber amplifier allows the user to describe the amplifier through either physical or system parameters by using silicate or fluoride glass fibers or any other material, provided the user can give a file that contains the amplifier's characteristics. The new model of a single-mode fiber allows the user to describe chromatic dispersion through a constant, a function, or a file (given by the user) and to take optionally into account the Kerr and the Raman effects and the polarization-mode dispersion. The simulation tools that are used to characterize the quality of an optical transmission system are also presented. To show the system's full range of capabilities in the optical domain, we describe examples of wavelength-division-multiplexing and soliton-transmission systems.

Gradient estimation for stochastic optimization of optical code-division multiple-access systems .I. Generalized sensitivity analysis

For optimizing the performance of optical code-division multiple-access (CDMA) systems, there is a need for determining the sensitivity of the bit-error rate (BER) of the system to various system parameters. Asymptotic approximations and bounds, used for system bit-error probabilities, seldom capture the sensitivities of the system performance. We develop single-run gradient estimation methods for such optical CDMA systems using a discrete-event dynamic systems (DEDS) approach. Specifically, computer-aided techniques such as infinitesimal perturbation analysis (IPA) and likelihood ratio (LR) methods are used for analyzing the sensitivity of the average BER to a wide class of system parameters. It is shown that the above formulation is equally applicable to time-encoded and frequency-encoded systems. Further, the estimates derived are unbiased, and also optimality of the variance of these estimates is shown via the theory of common random variates and importance sampling techniques.