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Kazuo Hotate - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis of optical-Coherence Function and its applications in distributed and multiplexed optical sensing
    Journal of Lightwave Technology, 2006
    Co-Authors: Kazuo Hotate, Zuyuan He
    Abstract:

    We have proposed and demonstrated in recent years a unique technique to synthesize the optical-Coherence Function by manipulating the frequency and the phase of lightwave. Based upon this technique, the synthesis of optical Coherence Function (SOCF), various distributed photonic sensing and optical-information-processing applications have been developed. In this paper, the principle of SOCF is summarized. A series of Functional optical-sensing systems, including fiber-optic reflectometries, distributed stress-location sensors, multiplexed fiber Bragg grating (FBG) sensors, are introduced. Fully distributed fiber-optic strain sensing systems by Brillouin frequency shift are highlighted, and a distributed sensor based on synthesized dynamic grating is also presented. Applications in two- or three-dimensional distributed measurements, such as optical tomography of scattering medium, are also reviewed.

  • Distributed photonic sensing with synthesized optical Coherence Function
    Optical Fibers: Applications, 2005
    Co-Authors: Kazuo Hotate
    Abstract:

    We have proposed and demonstrated that the optical Coherence Function can be synthesized into desired shapes by manipulating the optical frequency and the phase of the lightwave. Based upon this unique technique, the synthesis of optical Coherence Function, various distributed photonic sensing and optical information processing applications have been developed. In this paper, the principle of the synthesis of optical Coherence Function is summarized. A series of Functional optical sensing systems, including fiber-optic reflectometries, distributed stress location sensors, multiplexed FBG sensors, are introduced. Fully distributed fiber optic strain sensing systems per Brillouin frequency shift are highlighted, and synthesized dynamic grating based sensor is also presented. Applications in two- or three-dimensional distributed measurements, such as optical tomography of scattering medium, are also reviewed.

  • Application of synthesized Coherence Function to distributed optical sensing
    Passive Components and Fiber-based Devices, 2005
    Co-Authors: Kazuo Hotate
    Abstract:

    We have proposed and demonstrated that the optical Coherence Function can be sythesized into desired shapes by manipulating the optical frequency and the phase of the lightwave. Based upon this unique technique, the synthesis of optical Coherence Function, various distributed photonic sensing and optical information processing applications have been developed. In this paper, the principle of the synthesis of optical Coherence Function is summarized. A series of Functional optical sensing systems, including fiber-optic reflectometries, distributed stress location sensors, multiplexed FBG sensors, are introduced. Fully distributed fiber optic strain sensing systems per Brillouin frequency shift are highlighted, and synthesized dynamic grating based sensor is also presented. Applications in two- or three-dimensional distributed measurements, such as optical tomography of scattering medium, are also reviewed.

  • Application of synthesized Coherence Function to distributed optical sensing
    Measurement Science and Technology, 2002
    Co-Authors: Kazuo Hotate
    Abstract:

    We have proposed and developed a technique to synthesize an optical Coherence Function into arbitrary shapes. By using this technique, which we call the `synthesis of an optical Coherence Function', various distributed optical sensing schemes have been developed, which have no mechanical moving parts nor data calculation. In these schemes, we do not use a pulsed lightwave but instead use a continuous wave, whose correlation is controlled by frequency modulation or phase modulation. We have proposed a reflectometry system to diagnose fibre optic subscriber networks. Fibre optic distributed force sensing systems have also been developed, which are applicable to smart structures and security systems. In a similar way, we have proposed a system to measure strain distribution along an optical fibre through the Brillouin scattering caused in the fibre. Spatial resolution of just 1 cm has been demonstrated by this system, which is 100 times higher than the practical limitation of conventional pulsed-lightwave techniques. Such a high spatial resolution is suitable for smart material applications. Two- or three-dimensional distributed sensing has also been developed by this technique. An optical tomography system has been proposed, which has fewer mechanical moving parts. A system for surface shape measurement for a multi-layered object has also been developed

  • Distribution sensing of Doppler shift frequency by synthesis of optical Coherence Function
    Proceedings of the 41st SICE Annual Conference. SICE 2002., 2002
    Co-Authors: Kazuo Hotate, T. Yamauchi
    Abstract:

    We propose and demonstrate a novel method of distribution sensing of Doppler-shift frequency, by applying synthesis of delta-Function-like optical Coherence Function (SOCF) to laser Doppler velocimetry. SOCF is a technique to resolve longitudinal position information along one arm of a laser-interferometric system. Distribution of the Doppler frequency is successfully measured in experiments.

Aristide Dogariu - One of the best experts on this subject based on the ideXlab platform.

  • Non-evolving spatial Coherence Function.
    Optics letters, 2018
    Co-Authors: Cristian Hernando Acevedo, Aristide Dogariu
    Abstract:

    We present a general model for the spatial Coherence Function of random fields created by scattering elliptical, perfect vortex beams. Remarkably, as opposed to the free-space propagation of typical random fields, there are regimes where the spatial Coherence Function does not evolve. We demonstrate analytically, numerically, and experimentally that both the size and the shape of spatial correlations can be precisely controlled in a manner that is independent of propagation distance.

  • Wide-field interferometric measurement of a nonstationary complex Coherence Function
    Optics letters, 2017
    Co-Authors: Roxana Rezvani Naraghi, Heath Gemar, Mahed Batarseh, Andre Beckus, George K. Atia, Sergey Sukhov, Aristide Dogariu
    Abstract:

    Spatial Coherence Function (SCF) is a complex Function of two spatial coordinates that, in general, carries more information than the bare intensity distribution. A fast and quantitatively accurate measurement of the SCF is extremely important for a range of applications in optical sensing and imaging. Here, we demonstrate an efficient two-step procedure for measuring the full-field complex Coherence Function. The measurement relies on an optimized design of a wavefront shearing interferometer capable of characterizing spatially inhomogeneous fields over an extended angular domain. The measurement precision is confirmed by the excellent agreement with a numerical estimation based on Fresnel calculations. We demonstrate that the sensitivity and the measurement range afforded by our instrument permits us to reliably describe the differences in the complex Coherence Functions that are due to subtle modifications in the shape, position, and orientation of radiation sources.

V Freilikher - One of the best experts on this subject based on the ideXlab platform.

  • two frequency mutual Coherence Function and pulse propagation in random media
    Physical Review E, 2002
    Co-Authors: Gregory Samelsohn, V Freilikher
    Abstract:

    In this work an analysis of transient wave propagation in forward scattering random media is presented. The analysis is based on evaluation of the two-frequency mutual Coherence Function, which is an important quantity in itself since it provides a measure of the Coherence bandwidth. The Coherence Function is calculated by using the path integral technique; specifically, by resorting to a cumulant expansion of the path integral. In contrast to the formulas available in the literature, the solution obtained is not limited by the strength of disorder and applies equally well to both dispersive and nondispersive media, with arbitrary spectra of inhomogeneities. For the regime of weak scattering (or relatively short propagation distances) the first cumulant gives an excellent approximation coinciding with the results obtained earlier in a particular case of the Kolmogorov turbulence by solving the corresponding differential equation numerically. In the regime of strong scattering (long distances), which to our knowledge has not been covered previously, our solution demonstrates a different type of scaling dependence. It is shown that, even for power spectra with fractal behavior in a wide range of spatial frequencies, the Coherence Function is very sensitive to fine details of the spectrum at both small and large spatial scales. Using the cumulant expansion, the temporal moments of the pulsed wave propagating in a random medium are also considered. It is found that the temporal moments of the pulse are determined exactly by accounting for a corresponding number of the cumulants. In particular, the average time delay of the pulse is determined by the first cumulant, and the pulse width is obtained by accounting for the first two cumulants. Although the consideration of the problem is based on the model of a continuous medium, the results are also applicable to wave propagation in media containing discrete particles scattering predominantly in the forward direction.

Z. Zakrzewski - One of the best experts on this subject based on the ideXlab platform.

  • Componentwise Coherence Function of correlated periodically nonstationary random processes
    Radioelectronics and Communications Systems, 2017
    Co-Authors: I. N. Yavorskyj, R. Yuzefovych, I. Y. Matsko, Z. Zakrzewski
    Abstract:

    In this paper we consider a novel componentwise Coherence Function, which is determined by the cross-spectral densities of stationary components of periodically nonstationary random processes i.e. stationary correlated random processes, which modulate their carrier harmonics. The properties of the introduced Coherence Function are specified for the amplitude- and phase-modulated signals. Its graphical frequency dependencies have been obtained for the specified signal parameters. The advantages of componentwise Coherence Function in comparison with previously suggested integral Coherence Function are shown. We present the method for the selection of stationary modulating components, which is based on the frequency shift and low-pass filtration. The properties of selected components for the cases of amplitude- and phase-modulated processes are analyzed.

  • Coherence Function of interrelated periodically nonstationary random processes
    Radioelectronics and Communications Systems, 2016
    Co-Authors: I. N. Yavorskyj, R. Yuzefovych, I. Y. Matsko, Z. Zakrzewski
    Abstract:

    A Coherence Function characterizing the correlation between harmonic components of two signals that are described by periodically correlated random processes has been proposed. Such Function is shown to be invariant with regard to linear transformations of signals.Aformula for Coherence Function is concretized for the amplitude- and phase-modulated signals.

Moorad Alexanian - One of the best experts on this subject based on the ideXlab platform.

  • temporal second order Coherence Function for displaced squeezed thermal states
    Journal of Modern Optics, 2016
    Co-Authors: Moorad Alexanian
    Abstract:

    We calculate the quantum mechanical, temporal second-order Coherence Function for a single-mode, degenerate parametric amplifier for a system in the Gaussian state, viz. a displaced–squeezed thermal state. The calculation involves first dynamical generation at time t of the Gaussian state from an initial thermal state and subsequent measurements of two photons a time τ≥0 apart. The generation of the Gaussian state by the parametric amplifier insures that the temporal second-order Coherence Function depends only on τ, via τ/t, for the given Gaussian state parameters, Gaussian state preparation time t, and average number n¯ of thermal photons. It is interesting that the time evolution for displaced thermal states shows a power decay in τ/t rather than an exponential one as is the case for general, displaced–squeezed thermal states.

  • temporal second order Coherence Function for displaced squeezed thermal states
    arXiv: Quantum Physics, 2015
    Co-Authors: Moorad Alexanian
    Abstract:

    We calculate exactly the quantum mechanical, temporal second-order Coherence Function for a single-mode, degenerate parametric amplifier for a system in the Gaussian state, viz., a displaced-squeezed thermal state. The calculation involves first the generation of the Gaussian state and subsequent measurements of two photons a time $\tau \geq 0$ apart. The generation of the Gaussian state by the parametric amplifier insures that the temporal second-order Coherence Function depends only on $\tau$.