Aperture averaging for optimizing receiver design and system performance on free-space optical communication links

Yüksel, Heba; Milner, Stuart D.; Davis, Christophér C.

doi:10.1364/jon.4.000462

Cited by 79 publications

(37 citation statements)

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“…Measurements of the effect of the aperture size on scintillation index have been given in [167]. These measurements, made in intermediate strength turbulence, are in reasonable agreement with the weak turbulence formula given in [152] …”

Section: Fade Mitigation Techniquessupporting

confidence: 64%

A review of communication-oriented optical wireless systems

Borah

Boucouvalas

Davis

et al. 2012

J Wireless Com Network

187

104

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This article presents an overview of optical wireless (OW) communication systems that operate both in the short-(personal and indoor systems) and the long-range (outdoor and hybrid) regimes. Each of these areas is discussed in terms of (a) key requirements, (b) their application framework, (c) major impairments and applicable mitigation techniques, and (d) current and/or future trends. Personal communication systems are discussed within the context of point-to-point ultra-high speed data transfer. The most relevant application framework and related standards are presented, including the next generation Giga-IR standard that extends personal communication speeds to over 1 Gb/s. As far as indoor systems are concerned, emphasis is given on modeling the dispersive nature of indoor OW channels, on the limitations that dispersion imposes on user mobility and dispersion mitigation techniques. Visible light communication systems, which provide both illumination and communication over visible or hybrid visible/ infrared LEDs, are presented as the most important representative of future indoor OW systems. The discussion on outdoor systems focuses on the impact of atmospheric effects on the optical channel and associated mitigation techniques that extend the realizable link lengths and transfer rates. Currently, outdoor OW is commercially available at 10 Gb/s Ethernet speeds for Metro networks and Local-Area-Network interconnections and speeds are expected to increase as faster and more reliable optical components become available. This article concludes with hybrid optical wireless/radio-frequency (OW/RF) systems that employ an additional RF link to improve the overall system reliability. Emphasis is given on cooperation techniques between the reliable RF subsystem and the broadband OW system.

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Section: Fade Mitigation Techniquessupporting

confidence: 64%

A review of communication-oriented optical wireless systems

Borah

Boucouvalas

Davis

et al. 2012

J Wireless Com Network

187

104

View full text Add to dashboard Cite

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“…Once the inner and outer radii of the captured frames are determined, the same framing technique discussed previously is used in calculating the aperture averaging factor [2,3]. The better masking technique discussed above produced a more efficient aperture averaging factor results.…”

Section: L λmentioning

confidence: 99%

“…The weather conditions are mainly effective on the strength of the turbulence [2,3]. Strong turbulence theory is applied only when the intensity variance is bigger than '1' thus the intensity variance has to be measured beforehand [4,5].…”

Section: Introductionmentioning

confidence: 99%

Study of strong turbulence effects for optical wireless links

2012

Self Cite

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Strong turbulence measurements that are taken using real time optical wireless experimental setups are valuable when studying the effects of turbulence regimes on a propagating optical beam. In any kind of FSO system, for us to know the strength of the turbulence thus the refractive index structure constant, is beneficial for having an optimum bandwidth of communication. Even if the FSO Link is placed very well-high-above the ground just to have weak enough turbulence effects, there can be severe atmospheric conditions that can change the turbulence regime. Having a successful theory that will cover all regimes will give us the chance of directly processing the image in existing or using an additional hardware thus deciding on the optimum bandwidth of the communication line at firsthand.For this purpose, Strong Turbulence data has been collected using an outdoor optical wireless setup placed about 85 centimeters above the ground with an acceptable declination and a path length of about 250 meters inducing strong turbulence to the propagating beam. Variations of turbulence strength estimation methods as well as frame image analysis techniques are then been applied to the experimental data in order to study the effects of different parameters on the result. Such strong turbulence data is compared with existing weak and intermediate turbulence data. Aperture Averaging Factor for different turbulence regimes is also investigated.

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“…, I > 0, (93) where the on-axis mean irradiance I(0, L) = 1 and K v (x) is the modified Bessel function of the first kind.…”

Section: Pdf Of the Scintillationmentioning

confidence: 99%

“…As a result, the aperture essentially averages these variations by focusing the intensity pattern onto the detector, commonly referred to as aperture averaging. Many have studied this phenomenon in regard to FSOC performance [2,15,24,63,[91][92][93][94]. This research uses the principle of reciprocity to determine the optimal separation distance for multiple transmitters using ρ cw .…”

Section: Optical Transmitter and Receiver Designmentioning

confidence: 99%

Integrated approach to airborne laser communication

Louthain¹

2008

SPIE Proceedings

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Lasers offer tremendous advantages over RF communication systems in terms of bandwidth and security due to their ultra-high frequency and narrow spatial beamwidth. Unfortunately, atmospheric turbulence significantly increases the received power variation and bit error rate (BER) in free-space optical communication (FSOC) systems. Further, airborne optical communication systems require special considerations in size, complexity, power, and weight.If two or more laser beams are sufficiently separated so that their turbulence effects are uncorrelated (i.e. anisoplanatic), they can effectively "average out" turbulence effects. This requisite separation distance is derived for multiple geometries, turbulence conditions, and optical properties. In most cases and geometries, the angles ordered from largest to smallest are: phase uncorrelated angle (equivalent to the tilt uncorrelated angle and phase anisoplanatic angle), tilt isoplanatic angle, phase isoplanatic angle, scintillation uncorrelated angle (or scintillation anisoplanatic angle), and scintillation isoplanatic angle (θ ψ ind > θ T A > θ 0 > θ χ ind > θ χ 0 ). Conventional adaptive optics (AO) systems only correct for phase and cannot correct for strong scintillation, while multiple-transmitter systems use several transmission paths to "average out" effects of the strong scintillation by incoherently summing up the beams in the receiver.Since all three airborne geometries (air-to-air, air-to-ground, and ground-toair) are studied, a comparison of multiple-beam airborne laser communication system performance is presented for the first time. Wave optics simulations show that a combination of transmitter diversity, receiver and transmitter trackers, and adaptive thresholding can significantly reduce BER in an air-to-air FSOC system by over 10,000 times. As demonstrated in this work, two transmitters alone separated by only 31 cm (100 km path length, 1.55 µm wavelength, 4 km in altitude) provide a significant iv BER improvement over one transmitter, especially for the strong turbulence regime where the required SNR for a fixed BER is reduced by 9 dB. Including the tracking and adaptive thresholding techniques, resulted in a 13 dB overall improvement.Two beams also reduce the fade length, suggesting even greater improvement can be obtained when interleaving and forward error correction coding is implemented. Major Schmidt also knew when to hand me water and how to keep me on the road, since he had just finished his marathon.

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Aperture averaging for optimizing receiver design and system performance on free-space optical communication links

Cited by 79 publications

References 0 publications

A review of communication-oriented optical wireless systems

A review of communication-oriented optical wireless systems

Study of strong turbulence effects for optical wireless links

Integrated approach to airborne laser communication

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