Neural network equalisation for high-speed eye-safe optical wireless communication with 850 nm SM-VCSELs

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Osahon, Isaac N. O. and Kostakis, Ioannis and Powell, Denise and Meredith, Wyn and Missous, Mohamed and Haas, Harald and Tang, Jianming and Rajbhandari, Sujan (2024) Neural network equalisation for high-speed eye-safe optical wireless communication with 850 nm SM-VCSELs. Photonics, 11 (8). 772. ISSN 2304-6732 (https://doi.org/10.3390/photonics11080772)

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Abstract

In this paper, we experimentally illustrate the effectiveness of neural networks (NNs) as non-linear equalisers for multilevel pulse amplitude modulation (PAM-M) transmission over an optical wireless communication (OWC) link. In our study, we compare the bit-error-rate (BER) performances of two decision feedback equalisers (DFEs)—a multilayer-perceptron-based DFE (MLPDFE), which is the NN equaliser, and a transversal DFE (TRDFE)—under two degrees of non-linear distortion using an eye-safe 850 nm single-mode vertical-cavity surface-emitting laser (SM-VCSEL). Our results consistently show that the MLPDFE delivers superior performance in comparison to the TRDFE, particularly in scenarios involving high non-linear distortion and PAM constellations with eight or more levels. At a forward error correction (FEC) threshold BER of 0.0038, we achieve bit rates of ~28 Gbps, ~29 Gbps, ~22.5 Gbps, and ~5 Gbps using PAM schemes with 2, 4, 8, and 16 levels, respectively, with the MLPDFE. Comparably, the TRDFE yields bit rates of ~28 Gbps and ~29 Gbps with PAM-2 and PAM-4, respectively. Higher PAM levels with the TRDFE result in BERs greater than 0.0038 for bit rates above 2 Gbps. These results highlight the effectiveness of the MLPDFE in optimising the performance of SM-VCSEL-based OWC systems across different modulation schemes and non-linear distortion levels.

ORCID iDs

Osahon, Isaac N. O., Kostakis, Ioannis, Powell, Denise, Meredith, Wyn, Missous, Mohamed, Haas, Harald, Tang, Jianming and Rajbhandari, Sujan ORCID logoORCID: https://orcid.org/0000-0001-8742-118X;
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