Performance Analysis of a 16-QAM Directly Modulated OFDM Visible Optical Wireless Link Without External Modulators

Abstract

This paper presents a performance analysis of a directly modulated direct-detection orthogonal frequency division multiplexing-based visible light communication system designed for high-speed and low-complexity transmission. The proposed architecture employs 16-Quadrature Amplitude Modulation (16-QAM) and achieves a data rate of 15 Gbps over a 500 m line-of-sight link while eliminating the need for external optical modulators and transmission-line amplifiers. The system was modeled and evaluated in the OptiSystem environment using a 1024-point fast Fourier transform with 512 active subcarriers, a cyclic prefix, and a directly modulated laser operating at 550 nm. Performance was assessed in terms of bit error rate (BER), optical signal-to-noise ratio (OSNR), error vector magnitude (EVM), maximum Q factor, and received optical power. The results show that the proposed architecture maintains BER ≤ 10⁻³ when the OSNR is approximately 32 dB or higher, confirming the feasibility of reliable 16-QAM orthogonal frequency division multiplexing (OFDM) transmission without external amplification. In addition, the analysis demonstrates that beam divergence is a critical design factor, since larger divergence angles reduce received optical power density and degrade both BER and EVM. A comparison between theoretical and simulated received power shows close agreement, validating the adopted link-budget model. The results confirm that the proposed directly modulated OFDM architecture provides an energy-efficient and cost-effective solution for short-to-medium-range high-speed visible optical wireless communication.

Received: 18 February 2026 | Revised: 20 May 2026 | Accepted: 22 June 2026 Conflicts of Interest

The author declares that he has no conflicts of interest to this work.

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Author Contribution Statement

Mahmoud Alhalabi: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing – original draft, Writing – review & editing, Visualization, Project administration.