Reducing Inter-Core Crosstalk Impact via Code-Interleaving and Bipolar 2-PPM for Core-Multiplexed SAC OCDMA PON

Abstract

Inter-core crosstalk (XT), caused by closely spaced cores, is the principal challenging issue of implementing multicore fiber (MCF)-based optical networks as it limits the network performance severely. In this paper, we propose and demonstrate using bipolar M-ary pulse position modulation (PPM) signaling in conjunction with the code-interleaving (CI) technique to address the inter-core XT problem in MCF-based optical code-division multiple-access (OCDMA) passive optical networks (PONs) with spectral-amplitude coding employed as the coding scheme. The bit error rate of the proposed network is derived based on an accurate analysis for the statistics of the decision random variables, i.e., mean and variance. The analysis accounts for inter-core XT, optical beat noise, and receiver noise. In addition, a comparison between the performance of core-multiplexed OCDMA PON adopting the newly proposed techniques, namely, unipolar on-off keying (OOK) with CI and bipolar 2-PPM with CI and that adopting unipolar OOK without CI, is presented under both data rate and average photons per bit constraints. The obtained results show that bipolar 2-PPM and CI are capable of reducing the inter-core XT impact on the performance of MCF-based OCDMA PONs. Furthermore, bipolar 2-PPM with CI outperforms other schemes in terms of the number of supportable users and energy efficiency.