Department of Electrical and Electronics Engineering
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Item Wireless Communications & Networks (adaptation by V K Chaubey)(Pearson Education, 2009) Chaubey, V.K.Item Analysis of Optical WDM Network Topologies with Application of LRWC Under symmetric Erlang - C Traffic(Springer, 2008) Chaubey, V.K.This paper analyses an Optical WDM network model with application of Limited Range Wavelength Converters for online routing with a wavelength assignment scheme under symmetric Erlang-C traffic. Distinct wavelengths have been assigned to short and long hop connections by wavelength conversion besides attempt to reserve an identical wavelength across all nodes. Probabilistic model for traffic has been developed employing both ring and star topology networks. A mathematical model has been further devised and its call blocking probability has been enunciated. Compared performance analysis of both topologies has been presented with an investigation on collective impacts of various traffic parameters on transmission.Item High Speed Resonant Tunneling Diode Based on GaN & GaAs: A Modelling & Simulation Approach(CRC, 2008) Chaubey, V.K.The investigation of tunneling of particles through potential barriers in semiconductor quantum wells has recently attracted much attention. Special focus is laid on resonant tunneling structures because of its importance in the field of nanoscience and technology and its potential applications in very high speed functionality devices and circuits. Among the numerous nanoelectronic devices proposed and demonstrated, the III-V based RTD is perhaps the most promising candidate for digital circuit applications due to its negative differential resistance (NDR) characteristic, structural simplicity, inherent high speed, flexible design freedom, relative ease of fabrication and versatile circuit functionality. There is a good practical reason to believe that these RTDs may be the next device based on quantum confined heterostructures to make the transition from the world of research into practical application. In this work, we have worked with two materials GaAs and GaN which are most useful for building next generation quantum devices. Apart from studying the tunneling as an electrical phenomenon, we have investigated how light of different energies affect the tunneling process in the two compound semiconductor materials chosen. Tunneling Current variation with different energies of barriers, barrier heights and electron energies has been studied. Eigen states have been found for the barriers. The effect of bias across tunneling has been reported. Precise control of tunneling using gate control (RTT) or Base control (for bipolar device) is presented with an optical control. The change in refractive index of a semiconductor on interaction with photon is exploited to derive the relation between the band gap of a semiconductor and incident light. A Bandgap variation ultimately leads to re-alignment of quantum states hence impacting the tunneling mechanism.Item Estimation of Optimal Buffering parameters for dynamic traffic intensity and its Architectures(2005) Chaubey, V.K.In this paper, we have undertaken the mathematical formulation for determining the required buffering time based on the traffic intensity on an all-optical network. The effect of design parameters on optical network containing proper buffer and control circuitry has been evaluated. Some of the buffering architectures have been suggested to provide different buffering times as governed by the diurnal traffic requirementsItem Analysis of a CSMA/CA Optical Network with Application of Optical Buffers (FDLs) for Online Routing(IEEE, 2008-01) Chaubey, V.K.This paper proposes a new algorithm in an optical network using online routing with the application of optical buffers comprising of delay-lines (FDLs). The model for the algorithm has been theoretically developed and the corresponding call connection probability has been calculated. The limitation on the amount of delay permitted per packet has been addressed by limiting the number of delay-lines used in switch fabric of the network. The algorithm proposed is deterministic. It employs the concept of online routing to implement `look ahead' characteristics and thus aims to design an intelligent optical network. Keywords: FDL; TDM; AON; OPS; Look ahead; Deterministic delay-line transmission algorithm; Call connection probabilityItem Modal Characteristics of a doubly clad step- index optical fiber- general analytical approach(Canadian Science Publishing, 1988) Chaubey, V.K.Using a fairly rigorous approach, a general characteristic equation for a doubly clad step-index fibre has been derived under the assumption that the refractive-index difference between the inner and outer cladding is small. Two different profiles, i.e., the W profile and the staircase profile, have been treated together and a discussion of their common characteristics has been made. Cutoff conditions for low-order modes have been obtained. For a certain range of values of the transverse-phase parameter ratio, the singly-clad fibre has greater mode cutoff V numbers than those of a doubly clad fibre. The analysis anticipates the possibility of obtaining greater cutoff V numbers for W-profile fibres.Item Modal attenuation in a four-layer metal-clad planar waveguide with a semi-parabolically graded guiding layer — an analytical study(Elsevier, 1991-04) Chaubey, V.K.A general characteristic equation is derived for a four-layer metal-clad graded-index slab waveguide with a guiding layer having a semi-parabolic refractive index profile. The attenuation parameter for the lowest-order TE and TM modes are computed and the results are presented and compared with those obtained by Al-Bader and Jamid for the three-layer case. We make similar calculations for a waveguide with a step-index guiding layer. The attenuation is found to be less sensitive to a change of the guiding layer width in the case of the four-layered structure with a parabolically graded guiding layer than it is for the corresponding three-layered structure. This situation is reversed in the case of a step-index waveguide. Thus the proposed four-layer planar waveguide shows some polarization discrimination properties which are significantly different from those of the three-layer waveguide.Item Field Intensity and Power Confinement of Four-layer Slab Waveguides with Various Refractive Index Profiles in the Guiding Region(De Gruyter, 1994) Chaubey, V.K.Relative field intensity distributions in three differenttypes of structures, i.e. Step index Slab Waveguide(SSW), Semi-parabolic index Slab Waveguide (SPSW)and Parabolic index Slab Waveguide (PSW) have beenanalytically derived and computed. It is found that thefield in the guiding region is maximum in case of thePSW structure. Analytical expressions for the relativepower confinement factors have also been obtained.The applicability of these results in the estimation ofcoupling coefficient of some of the Distributed FeedBack (DFB) lasers have also been briefly shown.Item Frequency filtering in diffused optical planar waveguides(NISCAIR, 1999-03) Chaubey, V.K.Diffusion techniques have provided as alternative to thin-films technology for the fabrication of planar optical waveguides in CdS, ZnSe, LiNbO3, and LiTaO3 etc.Item Nonlinear crosstalk analysis in fiber Raman amplifiers(NISCAIR, 2003) Chaubey, V.K.Since the first low-loss fiber in 1970, fiber-optics emerged from being a laboratory curiosity to constitution a significant portion of the communications and sensors business