Evaluation of Three-Level Code Division Multiplexing for High-Quality Radio over Fiber Communication

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Radio over Fiber system (RoF) technology facilitates the transmission of wireless signals over optical fibers, which provides many benefits, including low signal loss, and immunity to electromagnetic interference. Despite these benefits, conventional RoF systems grapple with signal impairments and limited user capacity, as each user must be allocated a specific frequency. To address these limitations, this paper explores the implementation of the Three-Level Division Multiplexing (3LCDM) technique with RoF, a superior multiplexing strategy that allows two users to share a single channel, thereby doubling capacity. This innovative combination was evaluated for various cases using 2.4 GHz, 5 GHz, and the combination of 2.4 GHz and 5 GHz carrier frequencies, and its performance was compared with traditional RoF systems. Simulations were carried out using OptiSystem in cooperation with the MATLAB simulator. The findings of this study reveal that the 3LCDM-RoF system can accommodate twice the number of users as the conventional RoF system without the need for amplifiers. Furthermore, it supports higher bit rates and longer transmission distances. Specifically, the 3LCDM-RoF system achieved maximum data rates at maximum fiber length of 2 x 1.1 Gbps at 60 km, (2.4 GHz), 2 x 2 Gbps at 40 km (5 GHz), and 2 x 0.5 Gbps per channel at 43 km (combined 2.4 GHz and 5 GHz) respectively. Meanwhile, the conventional RoF with 2.4 GHz, 5GHz and the combination of 2.4 GHz and 5 GHz can only achieve maximum data rate at a maximum fiber length of 1.1 Gbps at 45 km, 1.6 Gbps at 35 km, and 0.4 Gbps at 35 km respectively