Acousto-optic modulator for emulating atmospheric fade in free-space optical communication systems

Katz, Evan J.; Chahine, Yousef K.; Vyhnalek, Brian E.; Tedder, Sarah A.

doi:10.1117/12.2546511

Cited by 3 publications

(2 citation statements)

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“…The discrete-time fading signal is synthesized in real-time and converted to a digital voltage signal 𝑉[𝑚] based on a transfer function constructed from the response of the acousto-optic modulator. 6 [6] This signal is sent to the 16-bit DAC at a sample rate of 10 ksamples/s. The output of the DAC drives the AOM which is used to modulate the optical signal from the test transmitter.…”

Section: Fade Emulation Systemmentioning

confidence: 99%

Performance of a real-time photon counting optical receiver in the presence of emulated channel fading

Downey,

Chahine,

Tedder

et al. 2024

Free-Space Laser Communications XXXVI

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Free-space optical communication links with terrestrial ground stations experience fading due to atmospheric scintillation and beam pointing. Fiber-coupled receiver systems experience additional fading at the interface between the fiber and free-space optics of the telescope. The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) has characterized a real-time photon-counting optical ground receiver system with an atmospheric fade emulation system. The receiver system is comprised of a fiber interconnect, an array of superconducting nanowire single photon detectors (SNSPDs), and a field programmable gate array (FPGA) based receive modem. Two fiber interconnect/detector architectures have been studied. One architecture uses a 70-mode photonic lantern coupled to seven single pixel SNSPDs. The other architecture uses a 10-mode few-mode fiber (FMF) coupled to a 15-pixel SNSPD array. The receiver system complies with the Consultative Committee for Space Data Systems (CCSDS) Optical Communications High Photon Efficiency Coding and Synchronization Standard, which uses serially concatenated convolutionally coded pulse-position modulation (SCPPM). The CCSDS standard is designed for use in low photon flux missions, including the Orion Artemis-II Optical (O2O) communications demonstration. The standard utilizes a convolutional symbol interleaver which can be resized to mitigate different fades. The fade emulation system employed in this work emulates scintillation-induced, pointing-induced, and coupling-induced fading. This paper gives an overview of the real-time optical receiver system and the fade emulation system. It presents tests results which show the impact of fading on the performance on the receiver. The test results show that in the presence of channel fading, the 70-mode photonic lantern outperforms the 10-mode FMF under higher (𝐷/𝑟 0 = 9) turbulence conditions due to high fiber-coupling-induced fading and fiber coupling loss on the 10-mode FMF. When operating in lower turbulence (𝐷/𝑟 0 = 4), the 10-mode FMF outperforms the 70-mode photonic lantern. The paper also shows a larger convolutional interleaver improves the system performance as long as the receiver does not lose acquisition.

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Section: Fade Emulation Systemmentioning

confidence: 99%

Performance of a real-time photon counting optical receiver in the presence of emulated channel fading

Downey,

Chahine,

Tedder

et al. 2024

Free-Space Laser Communications XXXVI

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“…This can be done in-lab by using a relatively fast modulator to attenuate the optical signal from the test transmitter. [7][8][9] To obtain the integration times required to characterize codeword error rate (CWER) performance, it is desirable to be able to synthesize fade vectors to modulate the signal continuously in real time for CWER tests that may run for many hours.…”

Section: Introductionmentioning

confidence: 99%

Statistical analysis of fading power vectors for real-time atmospheric channel emulation

Chahine

Katz

Vyhnalek

et al. 2023

Free-Space Laser Communications XXXV

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The design and testing of a free-space optical communication system requires assessment of the impact of random fluctuations in received power from a laser beam transmitted over an atmospheric channel. A number of methods for generating fading power vectors for in-lab emulation of an atmospheric channel have previously been reported. These techniques include spectral shaping and filtering of a signal from a normally distributed pseudo-random number generator, full wave optics simulations with random phase screens, and pre-recorded measurements from experimental free-space links. In this work, a statistical analysis of atmospheric fading is presented with the goal of producing a practical engineering model suitable for generating synthetic fade vectors in real-time for long-duration receiver testing with channel interleaving. Specifically, a parametric model is developed for turbulence-induced fade on space-to-ground links with large-aperture receivers, including aperture-averaging and the effects of aperture size on the instantaneous coupling efficiency for mode-limited receivers. In particular, we analyze the probability density function and temporal power spectrum for fluctuations of the coupling efficiency for few-mode fibers in a range of turbulence conditions.

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Reconfigurable Fading Testbed for the Investigation of COTS Transceivers in OFLs

Cantore,

Marasco,

Monopoli

et al. 2024

2024 11th International Workshop on Metrology for AeroSpace (MetroAeroSpace)

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Acousto-optic modulator for emulating atmospheric fade in free-space optical communication systems

Cited by 3 publications

References 0 publications

Performance of a real-time photon counting optical receiver in the presence of emulated channel fading

Performance of a real-time photon counting optical receiver in the presence of emulated channel fading

Statistical analysis of fading power vectors for real-time atmospheric channel emulation

Reconfigurable Fading Testbed for the Investigation of COTS Transceivers in OFLs

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