Experimental and Analytical Investigations of an Optically Pre-Amplified FSO-MIMO System With Repetition Coding Over Non-Identically Distributed Correlated Channels

This paper presents theoretical and experimental bit error rate (BER) results for a freespace optical (FSO) multiple-input-multiple-output system over an arbitrarily correlated turbulence channel. We employ an erbium-doped fiber amplifier at the receiver (Rx), which results in an improved Rx's...

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Bibliographic Details
Published in:IEEE access 2020, Vol.8, p.12188-12203
Main Authors: Priyadarshani, Richa, Bhatnagar, Manav R., Bohata, Jan, Zvanovec, Stanislav, Ghassemlooy, Zabih
Format: Article
Language:English
Subjects:
Adaptive optics
Amplifiers
Arbitrary correlation
ASE noise
Asymptotic properties
Bit error rate
Codes
Coding
Comparative studies
Correlation
Correlation analysis
diversity
Doped fibers
Encoding
Erbium
Error correction
experimental
free-space optical communications
gamma-gamma distribution
Mathematical analysis
MIMO (control systems)
MISO (control systems)
Optical noise
optical pre-amplifier
Optical receivers
Optical sensors
Repetition
Signal to noise ratio
spatial diversity
Spontaneous emission
Turbulence
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Summary:This paper presents theoretical and experimental bit error rate (BER) results for a freespace optical (FSO) multiple-input-multiple-output system over an arbitrarily correlated turbulence channel. We employ an erbium-doped fiber amplifier at the receiver (Rx), which results in an improved Rx's sensitivity at the cost of an additional non-Gaussian amplified spontaneous emission noise. Repetition coding is used to combat turbulence and to improve the BER performance of the FSO links. A mathematical framework is provided for the considered FSO system over a correlated non-identically distributed Gamma-Gamma channel; and analytical BER results are derived with and without the pre-amplifier for a comparative study. Moreover, novel closed-form expressions for the asymptotic BER are derived; a comprehensive discussion about the diversity order and coding gain is presented by performing asymptotic analysis at high signal-to-noise ratio (SNR). To verify the analytical results, an experimental set-up of a 2 x 1 FSO-multiple-input-single-output (MISO) system with pre-amplifier at the Rx is developed. It is shown analytically that, both correlation and pre-amplification do not affect the diversity order of the system, however, both factors have contrasting behaviour with respect to coding gain. Further, to achieve the target forward error correction BER limit of 3.8 × 10 -3 , a 2 × 1 FSO-MISO system with a pre-amplifier requires 6.5 dB lower SNR compared with the system with no pre-amplifier. Moreover, an SNR penalty of 2.5 dB is incurred at a higher correlation level for the developed 2 × 1 experimental FSO set-up, which is in agreement with the analytical findings.
ISSN:2169-3536
2169-3536
DOI:10.1109/ACCESS.2020.2964149