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

Abstract

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-tonoise ratio (SNR). To verify the analytical results, an experimental setup of a 2 × 1 FSO-multiple-inputsingle-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 setup , which is in agreement with the analytical findings.

Quality assessment for terrestrial digital video broadcast over optical wireless communication‐passive optical network under moderately turbulent regime with spatial diversity

“…For performance enhancement, repetitive coding 2 Â 2 MIMO is employed as spatial diversity technique with maximal ratio combining receiver which is known to out-perform other diversity techniques. 31,32 The VQA metrics for both SISO and MIMO links are reported for varying channel parameters and performance improvements are reported. For the sake of generality, two heterogeneous content videos are taken as reference with different spatial and temporal characteristics.…”

“…With this motivation, authors in this paper attempt to evaluate the performance of digital video broadcasting terrestrial (DVB‐T) video over OWC‐PON under moderate strength of turbulence regimes. For performance enhancement, repetitive coding 2 × 2 MIMO is employed as spatial diversity technique with maximal ratio combining receiver which is known to out‐perform other diversity techniques 31,32 . The VQA metrics for both SISO and MIMO links are reported for varying channel parameters and performance improvements are reported.…”

Developing Cost-Effective and High-Speed 40 Gbps FSO Systems Incorporating Wavelength and Spatial Diversity Techniques

“…Later, a set of collimating optics can be used to transmit the modulated optical signal for detection and further analysis. This practice not only helps in delivering an all-optical system that is capable of compensating for the loss of signal quality due to atmospheric adversities but also readily integrates with the existing optical backbone networks [48][49][50].…”

“…The receiver side uses a power combiner to collect the information received from four independent channels. This process essentially improves the prospectus of recovering reliable information by combining and averaging out power received from different paths [50]. In our investigation, we have set the number of simultaneous users to four while the rest of the procedure related to signal modulation and transmission over diversified wavelengths remains the same.…”

Power Efficiency Analysis of Spatial Diversity Based Vertical FSO Links With Pointing Error in Multiple Beam Transmissions

“…The novel closed-form BER expressions were presented in [14] for quadrature amplitude modulation (QAM) based orthogonal frequency division multiplexing (OFDM) radio over FSO by Málaga distributed channels with the pointing error. The analytical BER results for the correlated Gamma-Gamma channels were derived and verified by the experimental demonstrations [15]. Moreover, the effect of non-zero boresight pointing error was investigated for MIMO FSO systems [16].…”