Performance of the optical communication adaptive optics testbed
18 Aug 2005-Proceedings of SPIE (International Society for Optics and Photonics)-Vol. 5892, pp 589212
TL;DR: In this paper, the authors describe the current performance of an adaptive optics testbed for optical communication, which allows for simulation of night and day-time observing on a 1 meter telescope with a 97 actuator deformable mirror.
Abstract: We describe the current performance of an adaptive optics testbed for optical communication. This adaptive optics system allows for simulation of night and day-time observing on a 1 meter telescope with a 97 actuator deformable mirror.
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TL;DR: Adaptive optics (AO) as mentioned in this paper improves the communication performance of a free-space optical communication channel by concentrating the received power on the detector, and the degree of improvement with AO correction depends on the modulation format, and on modulation order when pulse position modulation is utilized.
Abstract: A free-space optical communication channel suffers degraded performance due to blurring and scintillation of the received signal caused by atmospheric turbulence. Adaptive optics (AO) improves the communication performance of such a channel by concentrating the received power on the detector. The degree of improvement with AO correction depends on the modulation format, and on the modulation order when pulse position modulation is utilized. Gains of up to 6 dB with AO have been experimentally validated in a laboratory test bed under simulated atmospheric conditions involving turbulence and background light. The fade statistics of the turbulent atmospheric channel have also been analyzed with and without AO correction.
11 citations
TL;DR: In this paper, the performance of the adaptive coherent fiber coupling (ACFC) technology was evaluated for free-space coherent optical communication systems with a 357-element AO unit.
9 citations
01 May 2005
TL;DR: In this paper, the performance of a laboratory-based, free-space optical communications system through the use of adaptive optics (AO) was evaluated using a commercially available avalanche photodiode detector (APD) for signal detection.
Abstract: We present predicted and experimentally measured gains in communications performance of a laboratory-based, free-space optical communications system through the use of adaptive optics (AO). A commercially available avalanche photodiode detector (APD) is used in the receiver for signal detection. Background noise and atmospheric turbulence field conditions were simulated in the laboratory using an integration sphere and a specially designed heater. At an uncoded bit-error rate (BER) of 0.3, a 5- to 6-dB gain in the received signal power is shown when AO correction is applied in the presence of high background and turbulence. The data stream was a 100-megabits per second (Mbps) pseudo-random bit sequence (PRBS), on–off-keying (OOK)-modulated, 1064-nm laser pulse train. I. Introduction Free-space optical communication through atmospheric turbulence suffers due to distortion of the signal field distribution in the detector focal plane and the spreading of the signal intensity. These aberrations result in spot sizes in the focal plane that are several times diffraction limited for the aperture and require larger photodetectors to capture the required number of signal photons for the desired link performance. For uniformly distributed sky background intensity, the larger detector collects proportionally more background photons and results in degraded link performance. In general, larger-area detectors limit the data rate realizable due to the lower bandwidths and can contribute to temporal distortion of the received signal. By using adaptive optics (AO) techniques, the atmosphere-induced wavefront aberrations can be corrected, and near-diffraction-limited focused spot sizes can be realized. This would enable the use of smaller, high-speed detectors with better spatial discrimination against the unwanted background noise.
8 citations
Cites background or methods from "Performance of the optical communic..."
...Experiment The AO optical communication test bed is described in detail in [11,12] and shown for reference in Fig....
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...The characterization of the system in terms of the atmospheric parameter ro was shown in [11]....
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...Calibration of the optical path—in particular, the received spot size with zoom setting—was shown in [11]....
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12 Feb 2009
TL;DR: In this paper, the authors describe the performance obtained with the latest developments of voice-coils deformable mirrors for the correction of atmosphere turbulence, and present the ALPAO Core Engine which is an open and flexible environment allowing fast developments of high performances adaptive optics.
Abstract: We describe the performances obtained with the latest developments of voice-coils deformable mirrors for the correction
of atmosphere turbulence. Thanks to the electro-magnetic principle of the deformable mirror, very large strokes are
obtained (more than 20μm) with a very large bandwidth (1 kHz). We further present the ALPAO Core Engine which is
an open and flexible environment allowing fast developments of high performances adaptive optics. We emphasize all
the benefits for free space optical communication.
1 citations
Cites methods from "Performance of the optical communic..."
...The integration of faster camera based on the E2V CCD39[11] chip for higher frame rate up to 2 kHz is currently being studied....
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01 Jan 2006
TL;DR: The Optical Communications Telescope Laboratory (OCTL) is a state-of-the-art facility located at 2.2km altitude on Table Mountain Wrightwood, CA as discussed by the authors, where the 1-m OCTL telescope tracks targets as close as 10 degrees to the sun, and satellites as low as 250-km.
Abstract: The Optical Communications Telescope Laboratory is a state-of-the-art facility located at 2.2-km altitude on Table Mountain Wrightwood, CA. Designed for nighttime and daytime operation, the 1-m OCTL telescope tracks targets as close as 10-degrees to the sun, and satellites as low as 250-km. Maximum slew rates are 10 deg/sec elevation and 20 deg/sec azimuth. Research projects at the OCTL include (i) passive and active satellite tracking of sun-illuminated and retro-reflecting satellites, (ii) technology development for safe laser beam transmission into deep space, (iii) line-of-sight cloud detection, and (iv) adaptive optics correction of atmosphere-induced optical wavefront aberrations. OCTL tracks LEO, MEO and HEO satellites and is authorized by various satellite owners to transmit 532-nm and 1064-nm laser beams to several of their retro-reflector bearing satellites. We have successfully demonstrated nighttime transmission to Stella and daytime and nighttime transmission to Ajisai. We have coordinated our strategies for safe laser transmission through navigable airspace with the FAA, and apply a JPL-developed three-tiered sensor system for safe laser beam propagation. The third tier is through coordination with the Laser Clearinghouse which provides daily predictive avoidance windows for transmission to target satellites. Backscatter from clouds along the uplink line-of-sight is measured by a 0.15 degree field-of-view 20-cm acquisition telescope bore sighted with the 1-m telescope transmitter. Designed for daytime wavefront correction, the ninety-seven actuator deformable mirror across the 1-m makes the OCTL adaptive optics system has one of the highest actuator densities in operation. This paper describes early results from these research areas.
1 citations
References
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TL;DR: In this article, the average resolution of very-long and very-short-exposure images is studied in terms of the phase and log-amplitude structure functions, whose sum is called the wave-structure function.
Abstract: A theoretical foundation is developed for relating the statistics of wave distortion to optical resolution. The average resolution of very-long- and very-short-exposure images is studied in terms of the phase- and log-amplitude-structure functions, whose sum we call the “wave-structure function.” Those results which are comparable are in agreement with the findings of Hufnagel and Stanley who studied the average modulation transfer function of long-exposure images. It is found that the average short-exposure resolution can be significantly better than the average long-exposure resolution, but only if the wave distortion does not include substantial intensity variation.
1,525 citations
TL;DR: In this paper, a closed-form solution for the Strehl ratio was derived for imaging systems with circular and annular pupils aberrated by primary aberrations, except in the case of coma, for which the integral form was used.
Abstract: Imaging systems with circular and annular pupils aberrated by primary aberrations are considered. Both classical and balanced (Zernike) aberrations are discussed. Closed-form solutions are derived for the Strehl ratio, except in the case of coma, for which the integral form is used. Numerical results are obtained and compared with Marechal’s formula for small aberrations. It is shown that, as long as the Strehl ratio is greater than 0.6, the Marechal formula gives its value with an error of less than 10%. A discussion of the Rayleigh quarter-wave rule is given, and it is shown that it provides only a qualitative measure of aberration tolerance. Nonoptimally balanced aberrations are also considered, and it is shown that, unless the Strehl ratio is quite high, an optimally balanced aberration does not necessarily give a maximum Strehl ratio.
175 citations
"Performance of the optical communic..." refers methods in this paper
...Figure 4 shows measured Strehl ratios converted to wavefront error using the Marechal [4] approximation S = e−(2π(WFE/λ)) 2 = e−σ 2 ....
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TL;DR: In this article, the bandwidth requirements for tracking through turbulence have been studied for the case in which a closed-loop transfer function of the form H(f) = (1 + if/f3dB)−1 is used.
Abstract: The bandwidth requirements for tracking through turbulence have been studied for the case in which a closed-loop transfer function of the form H(f) = (1 + if/f3dB)−1 is used. The results illustrate that the one-axis one-sigma (rms) jitter σθ is given by the expression σθ = (fT/f3dB)(λ/D), where λ is the wavelength of light used, D is the diameter of the tracking aperture, and fT is the fundamental turbulence-tracking frequency that is determined so that, when the servo bandwidth f3dB is equal to fT, σθ is equal to the diffraction angle λ/D. In practice a tracking system may measure one of various kinds of tilt. As a consequence both G tilt (obtained from a centroid measurement) and Z tilt (the direction that is defined by the normal to the plane that minimizes the mean-square wave-front distortion) have been evaluated in detail. The fundamental turbulence-tracking frequencies fTG and fTZ corresponding to the G tilt and the Z tilt, respectively, are found to be almost identical and are given by the expressions fTG = 0.331D−1/6λ−1[∫ dzCn2(z)V2(z)]1/2 and fTz = 0.368D−1/6λ−1[∫ dzCn2(z)V2(z)]1/2, where z is the range coordinate, Cn2() is the refractive-index structure function, and V() is the wind-velocity profile. For turbulence models that are applied to systems of interest the fundamental turbulence-tracking frequency that is defined by these expressions is about one ninth of fG, the Greenwood frequency associated with higher-order wave-front distortion. This illustrates the important point that the bandwidth that is necessary to control the turbulence-induced tilt is significantly less than the bandwidth that is necessary to control the turbulence-induced higher-order wave-front distortion.
100 citations
TL;DR: SciMeasure, in collaboration with Emory University and the Jet Propulsion Laboratory (JPL), has developed an extremely versatile CCD controller for use in adaptive optics, optical interferometry, and other applications requiring high-speed readout rates and/or low read noise as discussed by the authors.
Abstract: SciMeasure, in collaboration with Emory University and the Jet Propulsion Laboratory (JPL), has developed an extremely versatile CCD controller for use in adaptive optics, optical interferometry, and other applications requiring high-speed readout rates and/or low read noise. The overall architecture of this controller system will be discussed and its performance using both EEV CCD39 and MIT/LL CCID-19 detectors will be presented. Initially developed for adaptive optics applications, this controller is used in the Palomar Adaptive Optics program (PALAO), the AO system developed by JPL for the 200' Hale telescope at Palomar Mountain. An overview of the PALAO system is discussed and diffraction-limited science results will be shown. Recently modified under NASA SBIR Phase II funding for use in the Space Interferometry Mission testbeds, this controller is currently in use on the Micro- Arcsecond Metrology testbed at JPL. Details of a new vacuum- compatible remote CCD enclosure and specialized readout sequence programming will also be presented.
12 citations
"Performance of the optical communic..." refers background in this paper
...The CCD is an 80 × 80 pixel EEV39 [1]....
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