Band-edge absorption characteristics of semi-insulating indium phosphide under unified Franz-Keldysh and Einstein models

The foundational Franz-Keldysh effect and Einstein model are applied in this work to characterize semiconductor band-edge absorption—and its departures from ideality. We unify the Franz-Keldysh and Einstein models to fully characterize the field-induced tunneling of photoexcited electrons from degenerate valence bands into the conduction band, with encroachment into the band gap arising as an Urbach tail. Our unified model is implemented for semi-insulating indium phosphide (SI-InP) with strong agreement seen between the theoretical and experimental results for varied photon energies and electric fields

Asymptotically tight performance bounds for equal-gain combining over a new correlated fading channel

A recently proposed fading model which can be used to describe both line-of-sight and non-line-of-sight components of a fading channel is analyzed. The outage probability and error rate performance of equal-gain combining over arbitrary correlated Beaulieu-Xie fading channels is considered. Asymptoticallytight closed-form lower and upper bounds are derived and these analytical results are verified via Monte Carlo simulations.Applied Science, Faculty ofEngineering, School of (Okanagan)ReviewedFacult

Asymptotically tight performance bounds for selection diversity over Beaulieu-Xie fading channels with arbitrary correlation

A new (Beaulieu-Xie) fading model was recently proposed to describe line-of-sight and non-line-of-sight components in wireless channels. In this work, we consider both outage probability and error rate performance of selective combining over this new fading channel model with arbitrary channel correlation. Closed-form expressions are obtained for asymptotically tight upper and lower bounds. The analytical results are verified by Monte Carlo simulations.Applied Science, Faculty ofEngineering, School of (Okanagan)ReviewedFacult

Maximum Likelihood Estimation of the Lognormal-Rician FSO Channel Model

In this work, the on-going challenges are addressed for the application of the lognormal-Rician turbulence model to free-space optical communication systems. Maximum likelihood estimation is applied to characterize the lognormal-Rician turbulence model parameters, and the expectation-maximization algorithm is used to compute maximum likelihood estimates of the unknown parameters. The performance is investigated, by way of the mean square error, and it is found that the proposed technique can accurately characterize free-space optical communication channels over a wide range of turbulence conditions, with reduced demand on the quantity of data samples.Applied Science, Faculty ofEngineering, School of (Okanagan)ReviewedFacultyResearche

Undersampled differential phase shift on-off keying for optical camera communications with phase error detection

This paper introduces the design and implementation of an optical camera communication (OCC) system. Phase uncertainty and phase slipping caused by camera sampling are the two major challenges for OCC. In this paper, we propose a novel modulation scheme to overcome these problems. The undersampled differential phase shift on-off keying is capable of encoding binary data bits without exhibiting any flicker to human eyes. The phase difference between two consecutive samples conveys one-bit information which can be decoded by a low frame rate camera receiver. Error detection techniques are also introduced to enhance the reliability of the system. Furthermore, we present the hardware and software design of the proposed system. This low-cost communication system has been implemented with a Xilinx FPGA and a Logitech commercial camera. Experimental results demonstrate that a bit-error rate of 10-⁵ can be achieved with 7.15 microwatts received signal power over a link distance of 15 centimeters.Applied Science, Faculty ofEngineering, School of (Okanagan)ReviewedFacult

An investigation of semiconductor nanoparticles for application to all-optical switching

A practical all-optical switch is necessary to alleviate electronic bottlenecks in fibre optic networks. Thus, a new all optical switch is introduced here—exhibiting femtojoule switching energies and femtosecond switching times. The all optical switches use 40 μm dielectric spheres to direct high-intensity photonic nanojets into peripheral coatings of semiconductor nanoparticles. Semiconductor nanoparticle coatings of Si, CdTe, InP, and CuO are studied and found to yield switching energies of approximately 1 pJ, 500 fJ, 400 fJ, and 300 fJ with switching times of 2 ps, 2.3 ps, 900 fs, and 350 fs, respectively.Applied Science, Faculty ofEngineering, School of (Okanagan)ReviewedFacultyResearche

Free-space optical communications using on-off keying and source information transformation

Free-space optical communication using on-off keying (OOK) and source information transformation is proposed. It is shown that source information transformation allows the proposed system to detect the OOK signal without requiring the knowledge of instantaneous channel state information and the probability density function (pdf) of the turbulence model. Analytical expressions are derived for the pdf of the detection threshold, and an upper bound is obtained on the average bit error rate (BER). Numerical studies show that the proposed system can achieve comparable performance to the idealized adaptive detection system, with a greatly reduced level of implementation complexity and a signal-to-noise ratio performance loss of only 1:8 dB at a BER of 1 x 10-⁹ for a lognormal turbulence channel with σ = 0:25.Non UBCApplied Science, Faculty ofEngineering, School of (Okanagan)ReviewedFacultyResearche