Colin Reinhardt | University of Washington (original) (raw)
Papers by Colin Reinhardt
Laser Communication and Propagation through the Atmosphere and Oceans V
Laser Communication and Propagation through the Atmosphere and Oceans IV, 2015
Micro- and Nanotechnology Sensors, Systems, and Applications VII, 2015
Imaging and Applied Optics 2014, 2014
ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gat... more ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gated intensified-CCD imager applied to optical turbulence and atmospheric extinction and scattering characterization. Results of lab experiment, field test, and wave-optics propagation simulations are presented
Laser Communication and Propagation through the Atmosphere and Oceans III, 2014
Laser Communication and Propagation through the Atmosphere and Oceans III, 2014
ABSTRACT The selection of the "optimal" operating wavelength for Free Space Opt... more ABSTRACT The selection of the "optimal" operating wavelength for Free Space Optical (FSO) systems has been a subject of some ongoing controversy over the past several decades. Practical FSO systems have been found to suffer severe performance degradation in adverse atmospheric visibility conditions (high extinction/low-transmission) such as fog, haze, and other atmospheric aerosols (smoke, dust). Claims have been made that certain wavelengths offer generally superior performance and reduced attenuation for FSO system operation. We will revisit the problem of optical propagation through atmospheric particulates, and will show that the specific details of the selected aerosol size distribution function (SDF), which specifies the aerosol number density distribution by radius, and the corresponding wavelength-dependent complex refractive indices can significantly influence the total extinction/transmission behavior of various wavelengths and hence the choice of "optimal" wavelength. We will use a variety of realistic atmospheric SDFs to highlight the sensitivity of the "optimal" wavelength to the SDF composition details. A primary result will be a comparison illustrating extinction performance at selected wavelengths across the spectrum of visible to LWIR for a variety of realistic and clearly-defined atmospheric scenarios: urban, desert, maritime, with fogs, hazes, smoke, and dust.
Laser Communication and Propagation through the Atmosphere and Oceans, 2012
ABSTRACT The refractive index structure parameter C 2/n(z) as a function of vertical height z, is... more ABSTRACT The refractive index structure parameter C 2/n(z) as a function of vertical height z, is a key parameter describing the turbulent intensity of the atmosphere, and is important for modeling and predicting beam propagation behavior. Over the past several decades many vertical C 2/n models have been developed, many based on empirical data from field test campaigns involving difficult in situ measurements by radiosondes, or remote-sensing using scidar/lidar/radar techniques. Each model has its own set of limitations and caveats. We have developed an improved C 2/n parametric model for the maritime environment, which uses the Navy Surface-Layer Optical Turbulence model for the low-altitude surface boundary layer, and merges with a generalized Hufnagel-Valley model for the middle- and upper-altitudes (up to 24 km elevation). It takes inputs of local bulk meteorological measurements and forms an estimate of C 2/n based on Monin-Obukhov similarity theory. We present phase-screen wave-optics propagation simulations comparing our improved model with previous models, in terms of turbulence metrics such as Fried's atmospheric coherence width r0, the scintillation index, and the Strehl ratio for both the weak and strong turbulence regimes, for vertical and slant paths, and for various characteristic regimes of the ratio w0=r0, where w0 is the Gaussian beam waist radius.
Free-Space Laser Communications X, 2010
ABSTRACT We present some preliminary results from our recent free-space optical communications fi... more ABSTRACT We present some preliminary results from our recent free-space optical communications field test experiments in the foggy littoral environment along the coast of Point Loma, San Diego, conducted between October 2009 and June 2010. Our custom-built 850nm lasercomm system uses on-off keyed non-return-to-zero intensity-modulation and direct-detection to transmit pseudo-random bit sequences (PN-11 codes) at 250 Mbps over a 300m horizontal atmospheric path. We investigate improvements offered by using the latest Advanced Navy Aerosol Model to calculate the aerosol size-distribution function, a fundamental input to the radiative transfer code which we use to generate an estimate of the channel frequency response/impulse-response function. The estimated channel response function is used to design an equalization filter to correct signal distortion due to multiple-scattering effects and additive noise. We compare the performance of the Advanced Navy Aerosol Model against the more simplistic log-normal, Gaussian, and Mooradian Pt. Loma distributions. In this conference proceeding manuscript we are presenting only preliminary findings of our work in progress. Additional analysis, verification, and study is required before any final results can be posited from these preliminary findings.
Laser Communication and Propagation through the Atmosphere and Oceans II, 2013
ABSTRACT Current transmissometer designs can be physically bulky, electronically complex, and sus... more ABSTRACT Current transmissometer designs can be physically bulky, electronically complex, and susceptible to background light; ultimately limiting performance. We describe a novel transmissometer design based upon a modulated LED source and an AC-coupled receiver to improve upon the aforementioned shortcomings. The design aims to reduce both complexity and SWAP through the use of a high frequency modulation technique, while ultimately improving SNR and measurement range over a variety of atmospheric conditions. The instrument is a dynamic atmosphere and range transmissometer (DART). First we discuss the theory associated with our technique; particularly addressing how the effects of atmospheric turbulence are handled. Next, we describe the radiometry and calibration procedures for the transmitter and the receiver. We describe the instrument hardware and how the DART was built and tested in the laboratory. Finally, we discuss the field experiment to test the DART against a commercial unit over a 700m coastal path in San Diego. The processed data are compared with concurrent measurements from the Optec LPV-3 commercial transmissometer. Transmission data from the DART tracks the commercial instrument very well over varying atmospheric conditions.
Laser Communication and Propagation through the Atmosphere and Oceans III, 2014
ABSTRACT The characterization of atmospheric effects on a propagated laser beam is important to a... more ABSTRACT The characterization of atmospheric effects on a propagated laser beam is important to applications ranging from free-space optical communications to high-energy laser systems for ship defense. These applications are frequently developed for a dynamic propagation environment in which either one or both ends of the optical link are moving. The instruments are often constrained by size, weight, and power limitations due to the platforms on which they will be installed. The dynamic nature of the optical link induces several difficulties in link-path instrumentation: turbulence statistics on a continuously changing path are hard to interpret, and the optical instruments must be designed to maintain a high-quality link between beacon and receiver. We will review some of the scintillometer designs and we examine the associated data produced by these different instruments.
Imaging and Applied Optics 2014, 2014
ABSTRACT Machine learning methods improve performance of a novel atmospheric parameter estimation... more ABSTRACT Machine learning methods improve performance of a novel atmospheric parameter estimation algorithm for characterizing local atmospheric propagation channel optical turbulence, extinction, and scattering. Results of lab experiment, field test, and wave-optics propagation simulations are presented
Applied Optics, 2008
Fog is a highly dispersive medium at optical wavelengths, and the received pulse waveform may suf... more Fog is a highly dispersive medium at optical wavelengths, and the received pulse waveform may suffer significant distortion. Thus it is desirable to have the impulse response of the propagation channel to recover data transmitted through fog. The fog particle density and the particle size distribution both strongly influence the channel impulse response, yet it is difficult to estimate these parameters. We present a method using a dual-wavelength free-space optical system for estimating the average particle diameter and the particle number density and for approximating the particle distribution function. These parameters serve as inputs to estimate the atmospheric channel impulse response using simulation based on the modified vector radiative transfer theory. The estimated channel response is used to design a minimum mean-square-error equalization filter to improve the bit error rate by correcting distortion in the received signal waveform due to intersymbol interference and additive white Gaussian noise.
We consider an optical beam propagated through the atmosphere and incident on an object causing a... more We consider an optical beam propagated through the atmosphere and incident on an object causing a temperature rise. In clear air, the physical characteristics of the optical beam transmitted to the object surface are influenced primarily by the effect of atmospheric turbulence, which can be significant near the ground or ocean surface. We use a statistical model to quantify the expected power transfer through turbulent atmosphere and provide guidance toward the threshold of thermal blooming for the considered scenarios. The bulk thermal characteristics of the materials considered are used in a thermal diffusion model to determine the net temperature rise at the object surface due to the incident optical beam. These results of the study are presented in graphical form and are of particular interest to operators of high power laser systems operating over large distances through the atmosphere. Numerical examples include a CO 2 laser (λ ¼ 10.6 μm) with: aperture size of 5 cm, varied pulse duration, and propagation distance of 0.5 km incident on 0.1-mm copper, 10-mm polyimide, 1-mm water, and 10-mm glass/resin composite targets. To assess the effect of near ground/ocean laser propagation, we compare turbulent (of varying degrees) and nonturbulent atmosphere. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gat... more ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gated intensified-CCD imager applied to optical turbulence and atmospheric extinction and scattering characterization. Results of lab experiment, field test, and wave-optics propagation simulations are presented
ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gat... more ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gated intensified-CCD imager applied to optical turbulence and atmospheric extinction and scattering characterization. Results of lab experiment, field test, and wave-optics propagation simulations are presented
Obtaining accurate, precise and timely information about the local atmospheric turbulence and ext... more Obtaining accurate, precise and timely information about the local atmospheric turbulence and extinction conditions and
aerosol/particulate content remains a difficult problem with incomplete solutions. It has important applications in areas
such as optical and IR free-space communications, imaging systems performance, and the propagation of directed
energy. The capability to utilize passive imaging data to extract parameters characterizing atmospheric turbulence and
aerosol/particulate conditions would represent a valuable addition to the current piecemeal toolset for atmospheric
sensing.
Our research investigates an application of fundamental results from optical turbulence theory and aerosol extinction
theory combined with recent advances in image-quality-metrics (IQM) and image-quality-assessment (IQA) methods.
We have developed an algorithm which extracts important parameters used for characterizing atmospheric turbulence
and extinction along the propagation channel, such as the refractive-index structure parameter Cn2 , the Fried
atmospheric coherence width r0 , and the atmospheric extinction coefficient, from passive imagery. We analyze the algorithm performance using simulations based on modeling with turbulence modulation transfer functions.
An experimental field campaign was organized and data were collected from passive imaging through turbulence of
Siemens star resolution targets over several short littoral paths in Point Loma, San Diego, under conditions various
turbulence intensities. We present initial results of the algorithm’s effectiveness using this field data and compare
against measurements taken concurrently with other standard atmospheric characterization equipment. We also discuss
some of the challenges encountered with the algorithm, tasks currently in progress, and approaches planned for
improving the performance in the near future.
The performance of terrestrial free-space optical communications systems is severely impaired by ... more The performance of terrestrial free-space optical communications systems is severely impaired by atmospheric aerosol particle distributions where the particle size is on the order of the operating wavelength. For optical and near-infrared wavelengths, fog droplets cause multiple-scattering and absorption effects which rapidly degrade received symbol detection performance as the optical depth parameter increases (visibility decreases). Using a custom free-space optical communications system we measured field data in fog within the optical multiple-scattering regime. We investigate the behavior of the estimated channel transfer function using both real field-test data and simulated propagation data based on field-test conditions. We then compare the channel transfer function estimates against the predictions computed using a radiative-transfer theory model-based approach which we also developed previously for the free-space optical atmospheric channel.
We investigate the effects of beam wander on an uncorrected laser system. The goal is to enable a... more We investigate the effects of beam wander on an uncorrected laser system. The goal is to enable an accurate assessment of irradiance at a receiver or target for a shipboard laser system, and in this paper we show that a maritime surface layer turbulence model is important for an accurate vertical profile. The approach is to provide an appropriate and flexible hybrid between high fidelity surface layer similarity theory model and a parametric regression-based model.
IEEE Journal on Selected Areas in Communications, 2009
In order to improve the performance of terrestrial free-space optical communication systems in ad... more In order to improve the performance of terrestrial free-space optical communication systems in adverse visibility conditions, we present a method for estimation of the atmospheric channel impulse response function which governs the optical intensity propagation. This method reduces run-time computational demands and system complexity in comparison to our previously proposed dual-wavelength channel estimation technique. We consider propagation of optical wavelengths in fog, where the droplet diameters are close to the wavelength and thus scattering and absorption effects are significant. A method for rapid calculation of a channel response function based on estimating the effective optical depth of the channel and curve-fitting is described. The channel response estimate can then be used to design a receiver-side equalizer (minimum mean-squared error linear equalizer) to correct the signal distortion due to propagation through the dispersive channel. The channel estimates are based on parametric curve-fitting functions which have been developed using the modified-vector radiative transfer theory to model the channel response. The optimal fit parameters are found using particle-swarm optimization to minimize the simulated bit-error rate of the received signal.
Laser Communication and Propagation through the Atmosphere and Oceans V
Laser Communication and Propagation through the Atmosphere and Oceans IV, 2015
Micro- and Nanotechnology Sensors, Systems, and Applications VII, 2015
Imaging and Applied Optics 2014, 2014
ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gat... more ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gated intensified-CCD imager applied to optical turbulence and atmospheric extinction and scattering characterization. Results of lab experiment, field test, and wave-optics propagation simulations are presented
Laser Communication and Propagation through the Atmosphere and Oceans III, 2014
Laser Communication and Propagation through the Atmosphere and Oceans III, 2014
ABSTRACT The selection of the "optimal" operating wavelength for Free Space Opt... more ABSTRACT The selection of the "optimal" operating wavelength for Free Space Optical (FSO) systems has been a subject of some ongoing controversy over the past several decades. Practical FSO systems have been found to suffer severe performance degradation in adverse atmospheric visibility conditions (high extinction/low-transmission) such as fog, haze, and other atmospheric aerosols (smoke, dust). Claims have been made that certain wavelengths offer generally superior performance and reduced attenuation for FSO system operation. We will revisit the problem of optical propagation through atmospheric particulates, and will show that the specific details of the selected aerosol size distribution function (SDF), which specifies the aerosol number density distribution by radius, and the corresponding wavelength-dependent complex refractive indices can significantly influence the total extinction/transmission behavior of various wavelengths and hence the choice of "optimal" wavelength. We will use a variety of realistic atmospheric SDFs to highlight the sensitivity of the "optimal" wavelength to the SDF composition details. A primary result will be a comparison illustrating extinction performance at selected wavelengths across the spectrum of visible to LWIR for a variety of realistic and clearly-defined atmospheric scenarios: urban, desert, maritime, with fogs, hazes, smoke, and dust.
Laser Communication and Propagation through the Atmosphere and Oceans, 2012
ABSTRACT The refractive index structure parameter C 2/n(z) as a function of vertical height z, is... more ABSTRACT The refractive index structure parameter C 2/n(z) as a function of vertical height z, is a key parameter describing the turbulent intensity of the atmosphere, and is important for modeling and predicting beam propagation behavior. Over the past several decades many vertical C 2/n models have been developed, many based on empirical data from field test campaigns involving difficult in situ measurements by radiosondes, or remote-sensing using scidar/lidar/radar techniques. Each model has its own set of limitations and caveats. We have developed an improved C 2/n parametric model for the maritime environment, which uses the Navy Surface-Layer Optical Turbulence model for the low-altitude surface boundary layer, and merges with a generalized Hufnagel-Valley model for the middle- and upper-altitudes (up to 24 km elevation). It takes inputs of local bulk meteorological measurements and forms an estimate of C 2/n based on Monin-Obukhov similarity theory. We present phase-screen wave-optics propagation simulations comparing our improved model with previous models, in terms of turbulence metrics such as Fried's atmospheric coherence width r0, the scintillation index, and the Strehl ratio for both the weak and strong turbulence regimes, for vertical and slant paths, and for various characteristic regimes of the ratio w0=r0, where w0 is the Gaussian beam waist radius.
Free-Space Laser Communications X, 2010
ABSTRACT We present some preliminary results from our recent free-space optical communications fi... more ABSTRACT We present some preliminary results from our recent free-space optical communications field test experiments in the foggy littoral environment along the coast of Point Loma, San Diego, conducted between October 2009 and June 2010. Our custom-built 850nm lasercomm system uses on-off keyed non-return-to-zero intensity-modulation and direct-detection to transmit pseudo-random bit sequences (PN-11 codes) at 250 Mbps over a 300m horizontal atmospheric path. We investigate improvements offered by using the latest Advanced Navy Aerosol Model to calculate the aerosol size-distribution function, a fundamental input to the radiative transfer code which we use to generate an estimate of the channel frequency response/impulse-response function. The estimated channel response function is used to design an equalization filter to correct signal distortion due to multiple-scattering effects and additive noise. We compare the performance of the Advanced Navy Aerosol Model against the more simplistic log-normal, Gaussian, and Mooradian Pt. Loma distributions. In this conference proceeding manuscript we are presenting only preliminary findings of our work in progress. Additional analysis, verification, and study is required before any final results can be posited from these preliminary findings.
Laser Communication and Propagation through the Atmosphere and Oceans II, 2013
ABSTRACT Current transmissometer designs can be physically bulky, electronically complex, and sus... more ABSTRACT Current transmissometer designs can be physically bulky, electronically complex, and susceptible to background light; ultimately limiting performance. We describe a novel transmissometer design based upon a modulated LED source and an AC-coupled receiver to improve upon the aforementioned shortcomings. The design aims to reduce both complexity and SWAP through the use of a high frequency modulation technique, while ultimately improving SNR and measurement range over a variety of atmospheric conditions. The instrument is a dynamic atmosphere and range transmissometer (DART). First we discuss the theory associated with our technique; particularly addressing how the effects of atmospheric turbulence are handled. Next, we describe the radiometry and calibration procedures for the transmitter and the receiver. We describe the instrument hardware and how the DART was built and tested in the laboratory. Finally, we discuss the field experiment to test the DART against a commercial unit over a 700m coastal path in San Diego. The processed data are compared with concurrent measurements from the Optec LPV-3 commercial transmissometer. Transmission data from the DART tracks the commercial instrument very well over varying atmospheric conditions.
Laser Communication and Propagation through the Atmosphere and Oceans III, 2014
ABSTRACT The characterization of atmospheric effects on a propagated laser beam is important to a... more ABSTRACT The characterization of atmospheric effects on a propagated laser beam is important to applications ranging from free-space optical communications to high-energy laser systems for ship defense. These applications are frequently developed for a dynamic propagation environment in which either one or both ends of the optical link are moving. The instruments are often constrained by size, weight, and power limitations due to the platforms on which they will be installed. The dynamic nature of the optical link induces several difficulties in link-path instrumentation: turbulence statistics on a continuously changing path are hard to interpret, and the optical instruments must be designed to maintain a high-quality link between beacon and receiver. We will review some of the scintillometer designs and we examine the associated data produced by these different instruments.
Imaging and Applied Optics 2014, 2014
ABSTRACT Machine learning methods improve performance of a novel atmospheric parameter estimation... more ABSTRACT Machine learning methods improve performance of a novel atmospheric parameter estimation algorithm for characterizing local atmospheric propagation channel optical turbulence, extinction, and scattering. Results of lab experiment, field test, and wave-optics propagation simulations are presented
Applied Optics, 2008
Fog is a highly dispersive medium at optical wavelengths, and the received pulse waveform may suf... more Fog is a highly dispersive medium at optical wavelengths, and the received pulse waveform may suffer significant distortion. Thus it is desirable to have the impulse response of the propagation channel to recover data transmitted through fog. The fog particle density and the particle size distribution both strongly influence the channel impulse response, yet it is difficult to estimate these parameters. We present a method using a dual-wavelength free-space optical system for estimating the average particle diameter and the particle number density and for approximating the particle distribution function. These parameters serve as inputs to estimate the atmospheric channel impulse response using simulation based on the modified vector radiative transfer theory. The estimated channel response is used to design a minimum mean-square-error equalization filter to improve the bit error rate by correcting distortion in the received signal waveform due to intersymbol interference and additive white Gaussian noise.
We consider an optical beam propagated through the atmosphere and incident on an object causing a... more We consider an optical beam propagated through the atmosphere and incident on an object causing a temperature rise. In clear air, the physical characteristics of the optical beam transmitted to the object surface are influenced primarily by the effect of atmospheric turbulence, which can be significant near the ground or ocean surface. We use a statistical model to quantify the expected power transfer through turbulent atmosphere and provide guidance toward the threshold of thermal blooming for the considered scenarios. The bulk thermal characteristics of the materials considered are used in a thermal diffusion model to determine the net temperature rise at the object surface due to the incident optical beam. These results of the study are presented in graphical form and are of particular interest to operators of high power laser systems operating over large distances through the atmosphere. Numerical examples include a CO 2 laser (λ ¼ 10.6 μm) with: aperture size of 5 cm, varied pulse duration, and propagation distance of 0.5 km incident on 0.1-mm copper, 10-mm polyimide, 1-mm water, and 10-mm glass/resin composite targets. To assess the effect of near ground/ocean laser propagation, we compare turbulent (of varying degrees) and nonturbulent atmosphere. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gat... more ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gated intensified-CCD imager applied to optical turbulence and atmospheric extinction and scattering characterization. Results of lab experiment, field test, and wave-optics propagation simulations are presented
ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gat... more ABSTRACT Real-time measurement of local atmospheric propagation channel conditions with range-gated intensified-CCD imager applied to optical turbulence and atmospheric extinction and scattering characterization. Results of lab experiment, field test, and wave-optics propagation simulations are presented
Obtaining accurate, precise and timely information about the local atmospheric turbulence and ext... more Obtaining accurate, precise and timely information about the local atmospheric turbulence and extinction conditions and
aerosol/particulate content remains a difficult problem with incomplete solutions. It has important applications in areas
such as optical and IR free-space communications, imaging systems performance, and the propagation of directed
energy. The capability to utilize passive imaging data to extract parameters characterizing atmospheric turbulence and
aerosol/particulate conditions would represent a valuable addition to the current piecemeal toolset for atmospheric
sensing.
Our research investigates an application of fundamental results from optical turbulence theory and aerosol extinction
theory combined with recent advances in image-quality-metrics (IQM) and image-quality-assessment (IQA) methods.
We have developed an algorithm which extracts important parameters used for characterizing atmospheric turbulence
and extinction along the propagation channel, such as the refractive-index structure parameter Cn2 , the Fried
atmospheric coherence width r0 , and the atmospheric extinction coefficient, from passive imagery. We analyze the algorithm performance using simulations based on modeling with turbulence modulation transfer functions.
An experimental field campaign was organized and data were collected from passive imaging through turbulence of
Siemens star resolution targets over several short littoral paths in Point Loma, San Diego, under conditions various
turbulence intensities. We present initial results of the algorithm’s effectiveness using this field data and compare
against measurements taken concurrently with other standard atmospheric characterization equipment. We also discuss
some of the challenges encountered with the algorithm, tasks currently in progress, and approaches planned for
improving the performance in the near future.
The performance of terrestrial free-space optical communications systems is severely impaired by ... more The performance of terrestrial free-space optical communications systems is severely impaired by atmospheric aerosol particle distributions where the particle size is on the order of the operating wavelength. For optical and near-infrared wavelengths, fog droplets cause multiple-scattering and absorption effects which rapidly degrade received symbol detection performance as the optical depth parameter increases (visibility decreases). Using a custom free-space optical communications system we measured field data in fog within the optical multiple-scattering regime. We investigate the behavior of the estimated channel transfer function using both real field-test data and simulated propagation data based on field-test conditions. We then compare the channel transfer function estimates against the predictions computed using a radiative-transfer theory model-based approach which we also developed previously for the free-space optical atmospheric channel.
We investigate the effects of beam wander on an uncorrected laser system. The goal is to enable a... more We investigate the effects of beam wander on an uncorrected laser system. The goal is to enable an accurate assessment of irradiance at a receiver or target for a shipboard laser system, and in this paper we show that a maritime surface layer turbulence model is important for an accurate vertical profile. The approach is to provide an appropriate and flexible hybrid between high fidelity surface layer similarity theory model and a parametric regression-based model.
IEEE Journal on Selected Areas in Communications, 2009
In order to improve the performance of terrestrial free-space optical communication systems in ad... more In order to improve the performance of terrestrial free-space optical communication systems in adverse visibility conditions, we present a method for estimation of the atmospheric channel impulse response function which governs the optical intensity propagation. This method reduces run-time computational demands and system complexity in comparison to our previously proposed dual-wavelength channel estimation technique. We consider propagation of optical wavelengths in fog, where the droplet diameters are close to the wavelength and thus scattering and absorption effects are significant. A method for rapid calculation of a channel response function based on estimating the effective optical depth of the channel and curve-fitting is described. The channel response estimate can then be used to design a receiver-side equalizer (minimum mean-squared error linear equalizer) to correct the signal distortion due to propagation through the dispersive channel. The channel estimates are based on parametric curve-fitting functions which have been developed using the modified-vector radiative transfer theory to model the channel response. The optimal fit parameters are found using particle-swarm optimization to minimize the simulated bit-error rate of the received signal.