Ebad Zahir

SDM propagation model for multiple channels using electromagnetic theory and vortex analysis

Spatial Domain Multiplexing (SDM) is a novel technique in optical fiber communications. Single mode fibers are used to launch Gaussian beams of the same wavelength into a multimode step index fiber at specific angles. Based on the launch angle, the channel follows a helical path. The helical trajectory is explained with the help of vortex theory. The electromagnetic wave based vortex formation and propagation is mathematically modeled for multiple channels and the results are compared against experimental and simulated data. The modeled output intensity is analyzed to show a relationship between launch angle and the electric field intensity.

SDM propagation model for multiple channels using ray theory

Spatial Domain Multiplexing (SDM) is a novel optical fiber multiplexing technique where multiple channels of the same wavelength are launched at specific angles inside a standard step index multimode carrier fiber. These channels are confined to specific locations inside the fiber and they do not interfere with each other while traversing the length of the fiber. Spatial filtering techniques are employed at the output end to separate, route and process the individual channels. These skew ray channels inside the SDM system follow a helical trajectory along the fiber. The screen projection of the skew rays resembles a circular polygon. A ray theory based mathematical model of the SDM system is presented and simulated as well as experimental data is compared to the model predictions. This ray theory model utilizes launch point, input incidence angle, and point of incidence on fiber to explain the behavior of the individual channels. Thus the vector approach to propagation allows us to predict the effects of pulse spreading in the SDM system. The results showed that the skew ray trajectory is sensitive to input incidence angle. Similarly changing the launch point, while maintaining the angle of incidence constant with the z axis, can drastically affect the skew ray trajectory.

Analysis and optimization of an optical frequency comb for multiple channel transmission in a fiberoptic system

The proposed scheme was successful in generating equally spaced frequency combs by launching three continuous-wave pumps at 1 nm wavelength with 10 MHz linewidth using FWM in multiple highly non-linear fibers. Variations in pump power and frequency separations were explored to determine the effect of the input parameters on the frequency comb generation. The dispersion effect and EDFA length are shown to have a significant effect on the comb width as well. Results show that for an optimized number of pumps, the scheme is successful in generating the spectral lines for a specific bandwidth.

Impact of Radii Ratios on a Two-Dimensional Cloaking Structure and Corresponding Analysis for Practical Design at Optical Wavelengths

This work is an extension to the evaluation and analysis of a two-dimensional cylindrical cloak in the Terahertz or visible range spectrum using Finite Difference Time-Domain (FDTD) method. It was concluded that it is possible to expand the frequency range of a cylindrical cloaking model by careful scaling of the inner and outer radius of the simulation geometry with respect to cell size and/or number of time steps in the simulation grid while maintaining appropriate stability conditions. Analysis in this study is based on a change in the radii ratio, that is, outer radius to inner radius, of the cloaking structure for an array of wavelengths in the visible spectrum. Corresponding outputs show inconsistency in the cloaking pattern with respect to frequency. The inconsistency is further increased as the radii ratio is decreased. The results also help to establish a linear relationship between the transmission coefficient and the real component of refractive index with respect to different radii ratios which may simplify the selection of the material for practical design purposes. Additional performance analysis is carried out such that the dimensions of the cloak are held constant at an average value and the frequency varied to determine how a cloaked object may be perceived by the human eye which considers different wavelengths to be superimposed on each other simultaneously.

Design and characterization of Silicon On Insulator (SOI) based rib waveguides operating at 1550 nm for single mode transmission in integrated nanophotonics

In this paper, the characterization of single mode Silicon On Insulator (SOI) rib waveguides operating at 1550 nm wavelength is presented for three separate cases. The mode profile of the output is observed when two waveguides are joined together with the presence of a taper or a gap. The designed waveguides are analyzed at different geometrical conditions and then the results are used to design a splitter. The results of the splitter design are used to explore the boundary conditions for single mode operation.

Cascading of Dual Drive Mach Zehnder Modulator and Electro Absorption Modulator for producing an optical comb

A new scheme for generating a flat optical frequency comb using three Laser sources based on cascading of Dual Drive Mach Zehnder Modulator (DD-MZM) and Electro Absorption Modulator (EAM) through an optical nonlinear fiber loop is explored in this paper. A single RF signal of 25 GHz having different amplitudes feed into the two arms of DD-MZM and then feed the signal into EAM to modulate the pulse train. By controlling the DC bias of both modulators as well as the RF signal frequency, the scheme is successful in generating evenly spaced 15 flat comb lines among 25 lines with a spectral power variation of about 2dB.The paper compares the performance of the proposed scheme against other methods where only one modulator was used. The scheme is also analysed for producing an optimum number of spectral lines based on number of sources, channel spacing and RF signal frequency. Finally, the performance of the system was successfully evaluated in a preliminary WDM setup of five channels/modes at 10Gb/s for a channel of 1 km length. Results in the form of BER and Q factor are presented in this paper.

6 Wheeled Mars rover design for terrain traversing, equipment servicing, astronaut assistance and on-board testing

Since the success of the Mars Pathfinder, a new chapter of space exploration began focusing on reducing the complexity of the rover and making it more autonomous, multifunctional, lightweight even at extreme adversities. A student based design for a competition allowed the researchers in this paper to explore a design that would meet those requirements. This paper presents the design of a six wheeled, triangular shaped chassis, having multi suspension based rover. This rover is integrated with a 2.4GHz communication system that not only allows the rover to be operated from a distance of 1km, but also allows the researchers to collect soil samples and test them on board the rover using a Microlab box. The rover also shows superior maneuverability by being able to turn 360° on the spot and able to scale obstacles of almost 1 feet. The performance of the design was also tested at a global competition — University Rover Challenge 2016 organized by The Mars Society held at Utah, USA, where this design came in 8th for the Phobos category. This competition only invited 30 rovers out of the 63 that applied from 12 different countries.

Design and implemantation of a piezoelectric energy harvesting system using a super capacitor

A method of harvesting vibrational energy with a piezoelectric element using a step-down DC-DC converter suggested by previous references is investigated for application based circuits. Based on the experimental data the current found from the piezoelectric material was very low so a super capacitor was introduced to increase the output current and also to store the harvested piezoelectric energy. Results based on vibrations picked up from the blades of a small DC fan show that vibrational energy can be harvested and the design of the prototype was successful.

Object Detection by Estimation of the Spectral Attenuation Coefficient in the Submerged Medium

Underwater object detection has a considerable impact in the field of ocean technology. This paper presents a techniqueto detect a submerged object based on the mediums spectral attenuation coefficient by applying Beer-Lambert Law. The value of this coefficient is a function of the mediums composition, depth of the object,and wavelength of incident light. Experiments were performed in a swimming pool using objects of different colors at different depths to validate the mathematical model for object detection.