Showing papers by "Beijing University of Posts and Telecommunications published in 1989"
01 Jun 1989
TL;DR: The main details of a series of computer programs to implement an optimum design of the E-field distribution are presented in this paper, where the characteristic impedance and electric field are obtained for an asymmetric TEM cell.
Abstract: By using the Green's function/variational formulation with a new form of charge distribution, expressions for the characteristic impedance and electric (E-) field are obtained for an asymmetric TEM cell. The main details of a series of computer programs to implement an optimum design of the E-field distribution are presented in this paper.
35 citations
TL;DR: In this article, the crosstalk between channels in Raman amplification for two-channel WDM system is calculated, and it is shown that the conversion efficiency of RAM is very low.
Abstract: The crosstalk between channels in Raman amplification for two-channel WDM system is calculated. Theory shows that severe crosstalk can occur even in the linear amplification (or pump undepletion) region. To ensure small crosstalk, the signal gain and injected pump power should be limited to values well below the threshold of Raman amplification. As a numerical example, a 30-dB gain penalty and 3-dB pump power penalty occur when a 30-dB signal-to-interference ratio (SIR) is required. Thus, the conversion efficiency of Raman amplification in WDM systems is very low. >
31 citations
TL;DR: In this paper, an analysis method for metal-clad optical waveguide polarizers based on the equivalent current theory of optical couplings is presented, which has not been obtained before.
Abstract: An analysis method for metal-clad optical waveguide polarizers, which is based on the equivalent current theory of optical waveguide couplings, is presented. This theory is used to analyze the metal-clad optical waveguide polarizers and obtain analytic formulas, which have not been obtained before. The results of the theory are nearly coincident with that of numerical calculation and experiments. >
19 citations
TL;DR: Both theoretical and experimental proof of elliptical polarization and nonorthogonality of Zeeman laser output are given and a new formula for calculation of this orthogonal error has been derived which also provides a way to measure the anisotropy of the laser cavity.
Abstract: This paper gives both theoretical and experimental proof of elliptical polarization and nonorthogonality of Zeeman laser output. It verifies that the polarized modes of the output have 4–7° orthogonal error which is induced by anisotropy in the laser cavity. A new formula for calculation of this orthogonal error has been derived which also provides a way to measure the anisotropy of the laser cavity. We also discuss the influence of nonorthogonality on the spectrum of the laser.
17 citations
TL;DR: In this article, the authors derived analytic solutions of traveling-wave antennas excited by nonsinusoidal currents in the time domain by using a simple method, and obtained a solution that is almost the same as H. Harmuth's (Antennas and Waveguides for Nonsinusoidal Waves, New York: Academic, 1984, p.99-103).
Abstract: Analytic solutions of traveling-wave antennas excited by nonsinusoidal currents are derived in the time-domain by using a simple method. The solutions are explicit closed-form expressions. For the far-field approximation, a solution that is almost the same as H. Harmuth's (Antennas and Waveguides for Nonsinusoidal Waves, New York: Academic, 1984, p.99-103) is obtained. >
14 citations
TL;DR: In this paper, the relative intensity noise (RIN) Fourier spectrum of a semiconductor laser with arbitrary optical feedback has been derived, and it is shown that intensity noise can be highly suppressed at strong feedback, and that the phase of the feedback field plays an important role in the suppression of intensity noise.
Abstract: The relative intensity noise (RIN) Fourier spectrum of a semiconductor laser with arbitrary optical feedback has been derived. The authors calculations show that intensity noise can be highly suppressed at strong feedback, and that the phase of the feedback field plays an important role in the suppression of intensity noise. >
8 citations
TL;DR: In this article, a Ti: NiNbO3 polarization-independent modulator is described, which has two sets of electrodes with approximately equal applied voltages, and the drive voltages of TE and TM mode at 0.633 μm are about 15 and 11 V, respectively, with above 95% modulation.
Abstract: A Ti: NiNbO3 polarization-independent modulator is described, which has two sets of electrodes with approximately equal applied voltages. The drive voltages of TE and TM mode at 0.633 μm are about 15 and 11 V, respectively, with above 95% modulation.
7 citations
TL;DR: Short external cavities with strong optical feedback are found to reduce the noise dramatically in semiconductor lasers, especially in the high-frequency regime.
Abstract: The noise spectra and frequency chirping of semiconductor lasers in the presence of arbitrary amounts of optical feedback are analyzed. Short external cavities with strong optical feedback are found to reduce the noise dramatically in semiconductor lasers, especially in the high-frequency regime. Frequency chirping is shown to be closely related to the nonlinear gain effect.
6 citations
TL;DR: In this paper, the index mapping of one to two dimensions proposed by Burrus is generalised to one to multi dimensions and it is proven that this index mapping is equivalent to the index map proposed by Qian and Zhu.
Abstract: The index mapping of one to two dimensions proposed by Burrus is generalised to one to multi dimensions. It is proven that this index mapping is equivalent to the index mapping proposed by Qian and Zhu.
6 citations
TL;DR: In this paper, a coupled-mode equation for anisotropic waveguide systems of arbitrary cross section and general dielectric distribution is derived, where the edge-to-edge separation of two coupled guides D/sub 2/ is about 0.1 mu m.
Abstract: A coupled-mode equation for anisotropic waveguide systems of arbitrary cross section and general dielectric distribution is derived. Numerical results comparing the exact calculations to those of the method of Hardy et al. (Opt. Lett., vol.11, 742-4, 1986) show that the same accuracy can be obtained not only for TE, but also for TM mode coupling in the case of anisotropic waveguides, and the improved coupled-mode theory is applicable to the situation when moderately strong coupling occurs under the condition where the edge-to-edge separation of two coupled guides D/sub 2/ is about 0.1 mu m. >
5 citations
18 Sep 1989
TL;DR: In this paper, sliding electric contact experiments show that, in dusty environments, liquid lubricants appear to perform better than wax lubricants Experimental and theoretical analysis indicates that high permittivity of the lubricants plays an important role in attracting dust.
Abstract: Sliding electric contact experiments show that, in dusty environments, liquid lubricants appear to perform better than wax lubricants Experimental and theoretical analysis indicates that high permittivity of the lubricants plays an important role in attracting dust The mixture of dust particles and wax could be very harmful to the contact, especially under low normal force Dust particles floated on the surface of liquid droplets appear to have high mobility, which reduces the dust problem Electric current flowing through the contacts possibly melts the wax and decreases contact resistance On the contrary, electric current weakens the mobility and floating ability of dust on the liquid surface, which leads to an increase in resistance Simply reducing the contact size can cause the embedding of dust into wear tracks in low normal force applications >
TL;DR: In this paper, an external-cavity semiconductor laser consisting of a 1.3 mu m buried-heterostructure laser diode with an antireflection coated facet and a 4 mm GRINROD is presented.
Abstract: Results are presented of a study on an external-cavity semiconductor laser consisting of a 1.3 mu m buried-heterostructure laser diode with an antireflection coated facet and a 4 mm GRINROD. Due to its enclosed compact structure and strong optical feedback, it provides a stable single mode, with a mainside mode ratio of more than 30 dB, and is not sensitive to environmental perturbations. No mode jumping occurred during 12 h of continuous observation. The measured linewidth of 90 kHz is in good agreement with the newly developed theoretical calculation. >
18 Sep 1989
TL;DR: The effect of sliding wear on the rate of surface segregation of sulfur from an oxygen-free, highconductivity (OFHC) copper sample was investigated in an ultra-high-vacuum system having a residual gas pressure of 5*10/sup -11/ torr as discussed by the authors.
Abstract: The effect of sliding wear on the rate of surface segregation of sulfur from an oxygen-free, high-conductivity (OFHC) copper sample was investigated. The study was carried out in an ultra-high-vacuum system having a residual gas pressure of 5*10/sup -11/ torr. Wear tracks were formed on OFHC Cu that had previously been annealed and argon-ion sputter cleaned. A bent pin (palladium-based alloy, ASTM B540) was made to slide across the surface with a contact force of 25 g for 9000 cycles. Auger electron spectroscopy was used to characterize the composition of the surface on and off the wear track. No surface segregation was observed to occur as a result of forming the wear track. Subsequent in situ isothermal annealing between 310 degrees C and 470 degrees C produced S enhancement on the specimen surface. It was observed that the rate of S segregation on the wear track was much faster than off track up to approximately 390 degrees C, where this rate decreased significantly. At higher temperatures, the rate of S segregation on-track approximately equaled the off-track rate. The drop in the rate of S segregation on the track of 390 degrees C is attributed to annealing-out of the short-circuit diffusion paths associated with the defects formed when the wear track was made. The subsequent increase in S concentration at higher temperatures is due to the normal surface segregation phenomenon which occurs in annealed samples. >
TL;DR: The authors propose other modified Lu-Lee cryptosystems which use nonlinear encryption functions and the new system seem seem to be secure.
Abstract: Lu and Lee's cryptosystem has been proved to be insecure, and Adiga and Shankar's modified Lu-Lee system has been threatened by Kannan's algorithm. Here, the authors propose other modified Lu-Lee cryptosystems which use nonlinear encryption functions. The new system seem seem to be secure.
TL;DR: In this article, the authors extended the equivalent current theory to optical fibers composed of anisotropic material and derived analytical formulas for the radiation loss and the mode coupling in single-mode single-polarization fibers.
Abstract: In this letter we extend the equivalent current theory to optical fibers composed of anisotropic material. Analytical formulas for the radiation loss and the mode coupling in single-mode single-polarization fibers have been derived.
TL;DR: In this article, a semiclassical rate equation model has been established and the FM noise power spectrum calculated, and the spectral line width can be narrowed by the negative electrical feedback technique.
Abstract: In this paper, a semiclassical rate equation model has been established and the FM noise power spectrum calculated. We show that the spectral line width can be narrowed by the negative electrical feedback technique. Within the feedback loop bandwidth, the chirp-power-ratio (CPR) is reduced by a factor of 1+H, it shows that this kind of laser can be used as the light source in FSK coherent transmission system. Because of the direct modulation phase delay of the semiconductor laser, l/f-type FM noise is one of the important origin of the limitation, for linewidth reduction.
08 May 1989
TL;DR: In this article, a real lossless digital two-pair and a complex lossless 2-pair LBR filter are presented and used to realize n-cascade passive real and complex digital filters in the z-domain.
Abstract: A novel of real lossless digital two-pair and a complex lossless digital two-pair are presented and used to realize n-cascade passive real and complex digital filters in the z-domain. Any kind of filters can be realized by the method in canonic form. It is shown that LBR filters are the Z-domain realization of wave digital filters. >
TL;DR: In this paper, the thermal chemical effect in ion mixing of metal-metal systems was studied experimentally and through computer simulation, taking into account the chemical driving force, a simple model of ion mixing has been developed using the Monte Carlo code TCIS-4.
TL;DR: With this method a computer program in FORTRAN language is realized on the computers FELIX C-512 and IBM-PC, and good results are obtained in practical operations.
Abstract: Some new concepts of effective incidence matrix, ascending order adjacency matrix and end-result vertex are introduced, and some improvements of the maximum weight matching algorithm are made. With this method a computer program in FORTRAN language is realized on the computers FELIX C-512 and IBM-PC. Good results are obtained in practical operations.
TL;DR: In this article, the authors present a complete analysis of frequency chirping in negative electrical feedback (NEFB) semiconductor lasers by using the semiclassical rate equation model and show that this kind of noise is an important origin of the linewidth reduction limitation.
Abstract: In this letter we will present a complete analysis of frequency chirping in negative electrical feedback (NEFB) semiconductor lasers by using the semiclassical rate equation model. The effects of 1/f-type FM noise also will be discussed. Our result shows that this kind of noise is an important origin of the linewidth reduction limitation.
TL;DR: In this article, a navel linear mode extinction modulator using a LiNbO3 curved waveguide is proposed and analyzed using the loss model, and the modulation characteristics are predicted then.
Abstract: In this paper a navel linear mode extinction modulator using a LiNbO3 curved waveguide is proposed and analyzed using the loss model [1]. The modulation characteristics are predicted then.
01 Jun 1989
TL;DR: In this article, a T-cascade passive digital filter synthesis method is presented to realize real and complex digital filters in the z-domain in canonic form, and a complex lossless two-pair is proposed to realize complex filters.
Abstract: A T-cascade passive digital filter synthesis method is presented to realize real and complex digital filters in the z-domain. Symmetric and antimetric digital filters can be realized by this method in canonic form. A complex lossless two-pair is proposed to realize complex filters. The real lossless two-pair is its special case. A new real lossless two-pair is derived from the complex one to realize real antimetric filters. Two examples are discussed. >
01 Jun 1989
TL;DR: For the case where the input signal is a superposition of many sinusoids, the Volterra modeling of a nonlinear system in a discrete frequency domain is given and a computer algorithm is proposed.
Abstract: A method for measuring first/second Volterra kernels in the frequency domain is given. For the case where the input signal is a superposition of many sinusoids, the Volterra modeling of a nonlinear system in a discrete frequency domain is given. Using this model and carefully choosing input frequencies, one can measure the first/second Volterra kernels at many points simultaneously. A computer algorithm is proposed, and simulation results that show the efficiency of this method, are given. >
01 Jun 1989
TL;DR: In this paper, a method for designing multidimensional wave digital filters is presented in terms of non-reciprocal circulators, the principle of reflected filters, and the theory of one-dimensional general parameter filters, with complex attenuation poles.
Abstract: A method for designing multidimensional wave digital filters is presented in terms of nonreciprocal circulators, the principle of reflected filters, and the theory of one-dimensional general parameter filters, with complex attenuation poles. Both attenuation and group delay responses are considered in the approximation in order to derive its wave digital realization by linear transformation. An example of designing a two-dimensional reference filter is given, and its two-dimensional wave digital realization is derived as well. >
Proceedings Article•
01 Jan 1989TL;DR: In this paper, it is shown that in the training phase, it is possible to extract the spectral information for all the words to be recognized and the noise reduction filter for each word can thus be constructed from this spectral information.
Abstract: Summary form only given In speech recognition, training and recognition processes can be conducted in different environments For example, the word pattern may be extracted from clean speech, while the recognition may take place in background noise Further more, since the vocabulary size is limited, it is possible, in the training phase, to extract the spectral information for all the words to be recognized The noise reduction filter for each word can thus be constructed from this spectral information >
11 Jun 1989
TL;DR: The authors develop a model in which echo and intersymbol interference (ISI) can be eliminated simultaneously and application of an adaptive cancellation, instead of the inverse filtering, to eliminate ISI is developed.
Abstract: The authors develop a model in which echo and intersymbol interference (ISI) can be eliminated simultaneously. The features of the proposed model include: (1) low-complexity echo cancellation with faster convergence than the traditional configuration, the number of multiplications and tap coefficients required being between 25% and 37.5% and 16.7% and 25%, respectively, of those of the traditional configuration; (2) application of an adaptive cancellation, instead of the inverse filtering, to eliminate ISI, so that the dependence of the convergence behaviors of equalizers on the channel characteristics, a problem common to the traditional method for elimination of ISI, is removed. >
TL;DR: In this paper, a new intrinsic bistable optical device which is made of thin-film planar optical waveguide and liquid crystal and obtained perfect experimental results with approximate rectangular optical hysteresis loop.
23 May 1989
TL;DR: A hyperstable adaptive algorithm that can be used in the multichannel IIR (infinite impulse response) configuration and permits the high-order IIR or zero-pole configuration to be realized in the parallel form for joint process estimation is developed.
Abstract: The authors develop a hyperstable adaptive algorithm that can be used in the multichannel IIR (infinite impulse response) configuration and permits the high-order IIR or zero-pole configuration to be realized in the parallel form for joint process estimation The multichannel IIR configuration cannot be implemented by using the conventional hyperstable algorithm The high-order configuration implemented by the proposed algorithm has much better rounding-error performance than that implemented by the direct-form configuration Simulations results are presented for both the parallel zero-pole and multichannel configurations >
01 Jun 1989
TL;DR: It is proved that the relations between the Volterra kernels of these models can help one to identify the inner structure of open-loop nonlinear systems which contain only one nonlinearity.
Abstract: A method is described to identify the inner structure of open-loop nonlinear systems using Volterra kernels in the frequency domain. By applying Volterra functional series theory to the systems, one can obtain a criterion for the inner structure of nonlinear systems which contain only one nonlinearity. When the input is a single-frequency sinusoid signal, one can divide this system into five kinds through measuring the Mf loci. After it is shown that the system has an open-loop structure, various models are discussed, and it is proved that the relations between the Volterra kernels of these models can help one to identify the inner structure in more detail. >