Current Issue : April - June Volume : 2014 Issue Number : 2 Articles : 5 Articles
With the increasing input power in optical fibers, the dispersion problem is becoming a severe restriction on wavelength division\r\nmultiplexing (WDM).With the aid of solitons, in which the shape and speed can remain constant during propagation, it is expected\r\nthat the transmission of nonlinear ultrashort pulses in optical fibers can effectively control the dispersion. The propagation of a\r\nnonlinear ultrashort laser pulse in an optical fiber, which fits the high-order nonlinear Schr�¨odinger equation (NLSE), has been\r\nsolved using the G??/G expansion method. Group velocity dispersion, self-phase modulation, the fourth-order dispersion, and the\r\nfifth-order nonlinearity of the high-order NLSE were taken into consideration. A series of solutions has been obtained such as the\r\nsolitary wave solutions of kink, inverse kink, the tangent trigonometric function, and the cotangent trigonometric function. The\r\nresults have shown that the G??/G expansion method is an effective way to obtain the exact solutions for the high-order NLSE, and\r\nit provides a theoretical basis for the transmission of ultrashort pulses in nonlinear optical fibers....
Minimizing the bright/shadow focal spot size for differently polarized incident waves through the additional apodization of the\r\nfocusing system output pupil by use of an optical element with the vortex phase dependence on angle and the polynomial amplitude\r\ndependence on radius is studied. The coefficients of the radial polynomial were optimized with the aim of fulfilling certain\r\nconditions such as the energy efficiency preservation and keeping the side lobes under control. The coefficients were chosen so\r\nas to minimize the functional using Brent�s method....
Laser microwelding has been an essential tool with a reputation of rapidity and precision for joining miniaturized metal parts. In\r\nindustrial applications, an accurate prediction of weld bead geometry is required in automation systems to enhance productivity of\r\nlaser microwelding. The present work was conducted to establish an intelligent algorithm to build a simplified relationship between\r\nprocess parameters and weld bead geometry that can be easily used to predict the weld bead geometry with a wide range of process\r\nparameters through an artificial neural network (ANN) in laser microwelding of thin steel sheet. The backpropagation with the\r\nLevenberg-Marquardt training algorithm was used to train the neural network model. The accuracy of neural network model\r\nhas been tested by comparing the simulated data with actual data from the laser microwelding experiments. The predictions of\r\nthe neural network model showed excellent agreement with the experimental results, indicating that the neural network model\r\nis a viable means for predicting weld bead geometry. Furthermore, a comparison was made between the neural network and\r\nmathematical model. It was found that the developed neural network model has better prediction capability compared to the\r\nregression analysis model....
Photonic signal processing is used to implement common mode signal cancellation across a very wide bandwidth utilising phase\r\nmodulation of radio frequency (RF) signals onto a narrow linewidth laser carrier. RF spectra were observed using narrowband,\r\ntunable optical filtering using a scanning Fabry Perot etalon.Thus functions conventionally performed using digital signal\r\nprocessing techniques in the electronic domain have been replaced by analog techniques in the photonic domain. This technique\r\nwas able to observe simultaneous cancellation of signals across a bandwidth of 1400MHz, limited only by the free spectral range of\r\nthe etalon....
Fiber optic components offer a competitive implementation for applications exploiting the millimeter-wave and THz regimes\r\ndue to their capability for implementing broadband, compact, and cost-effective systems. In this paper, an outline of the latest\r\ntechnology developments and applications of fiber-optic-based technologies for the generation, transmission, and processing of\r\nhigh-frequency radio signals is provided....
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