Showing papers by "Er'el Granot published in 2002"

Method and apparatus for imaging absorbing objects in a scattering medium

Abstract: A method and processing device are presented for reconstructing an absorption and/or scattering image of a region of interest inside a scattering medium. A mathematical model is provided being representative of a relation between the distribution of the intensity and phase of electromagnetic radiation components scattered from a medium and a certain attenuation factor, which is function of spatial variations of scattering and absorption coefficients of the medium. The mathematical is used for processing a map of distribution of the intensity of electromagnetic radiation components scattered from known locations within the region of interest, thereby producing a halftone pattern of the region of interest.

Narrow Spectral Response of a Brillouin Amplifier transmission channel

Abstract: We investigate the spectral response of a Brillouin amplifier in the frequency regime within the SBS bandwidth. This is done by amplitude modulating the pump with a low frequency, and therefore, unlike previous studies, the spectrum of the modulated pump is, in all cases, smaller than the SBS bandwidth. We show both theoretically and experimentally that unlike phase modulation, which was reported in the literature, the amplitude modulation increases the Brillouin amplifier gain, and that this effect has a very narrow bandwidth. Only modulation frequencies that are lower than a certain cut-off frequency increase the gain. This cut-off frequency is inversely proportional to the fiber's length, and can therefore be arbitrarily small.

Emergence of a confined state in a weakly bent wire

Abstract: In this paper we use a simple straightforward technique to investigate the emergence of a bound state in a weakly bent wire. We show that the bend behaves like an infinitely shallow potential well, and in the limit of small bending angle $(\ensuremath{\varphi}\ensuremath{\ll}1)$ and low energy the bend can be presented by a simple one-dimensional $\ensuremath{\delta}$-function potential, $V(x)=\ensuremath{-}(2\sqrt{{c}_{b}}{\ensuremath{\varphi}}^{2})\ensuremath{\delta}(x)$ where ${c}_{b}\ensuremath{\cong}2.1.$

Method and apparatus for generating optical signals

Abstract: There is therefore provided, in accordance with an embodiment of the present invention, a method for processing an amplitude modulated (AM) optical beam amplitude modulated with a modulation pattern having an extinction ratio (ER), said AM beam having a carrier frequency and a carrier frequency amplitude, the method comprising: estimating an absolute amplitude extremum for the AM beam that is either an absolute amplitude maximum or an absolute amplitude minimum, to which recurrent amplitude extrema of the AM beam are approximately equal; estimating a corresponding phase to which the phase of the AM beam is substantially equal whenever the amplitude of the AM beam is substantially equal to the amplitude extremum; and adjusting at least one of the magnitude and phase of the carrier amplitude of the AM beam responsive to the amplitude extremum and its corresponding phase to increase the extinction ratio of the modulation pattern. The optical processing is carried out in a Brillouin Fiber grating formed by stimulated Brillouin scattering (SBS).

Forbidden activation levels in a non-stationary tunneling process

Abstract: Tunneling in the presence of an opaque barrier, part of which varies in time, is investigated numerically and analytically in one dimension. Clearly, due to the varying barrier a tunneling particle experiences spectral widening. However, in the case of strong perturbations, the particles’ activation to certain energies is avoided . We show that this effect occurs only when the perturbation decays faster than t −2 .

Limitations to bit-rate and spatial capacity of an optical data transmission channel

Abstract: The maximum bit-rate of a slab waveguide is ultimately determined by the waveguide dispersion. We show that while the maximum bit rate in a waveguide is inversely proportional to the waveguide's width, bit rate per unit width (i.e., spatial capacity) decreases, and in the limit of a zero-width waveguide it converges to a value, which is independent of the waveguide's refractive indices. This value is qualitatively equivalent to the transmission rate per unit of width in free space. We also show that in a 3D waveguide (e.g., fibers), unlike free space, the spatial capacity vanishes in the same limit.

Limitations to bit rate and spatial capacity of an optical data transmission channel

Abstract: The maximum bit rate of a slab waveguide is ultimately determined by the waveguide dispersion. We show that while the maximum bit rate in a waveguide is inversely proportional to the waveguide's width, the bit rate per unit width (i.e., spatial capacity (SC)) decreases, and in the limit of a zero-width waveguide it converges to ~ ω/√(λL) (where L is the length and ω and λ are the beam frequency and wavelength respectively). This result, which is independent of the waveguide's refractive indices, is qualitatively equivalent to the transmission rate per unit of width in free space. We also show that in a three-dimensional waveguide (e.g., fibres), unlike free space, the SC vanishes in the same limit.