Design and Analysis of a Spectrally Efficient Adaptive Polarization-Multiplexed OFDM System Using Novel CSD Code Encoding

This paper introduces a spectrally efficient adaptive polarization-multiplexed OFDM system that uses a short, low-cross-correlation CSD code. It also incorporates hybrid optical amplifiers to improve multi-user performance. The proposed CSD code offers a short code length with negligible cross-correlation. The adaptive polarization-multiplexing method then adjusts the polarization phase difference and the power split ratio based on receiver feedback. Together, these techniques increase user capacity and reduce BER. This adaptive process also lowers polarization-dependent loss and balances power between polarization states. As a result, it improves SNR and achieves a lower Bit Error Rate compared to conventional polarization-multiplexing schemes. The simulations demonstrate the practical feasibility of the proposed system by successfully recovering user data. The analytical results further show that, at a per-user rate of 622 Mbps, the system can accommodate up to 184 users at a BER of 10⁻⁹. This represents a 72% and 84% increase in capacity compared to existing ZCC, MDW, and FCC-coded OFDM-OCDMA systems. These gains are achieved using advanced adaptive polarization multiplexing combined with CSD coding. Optimal system performance occurs at a balanced polarization split ratio, α = 0.5, and zero phase difference, ɸ = 0°, with deviations significantly reducing capacity. By combining CSD coding, adaptive polarization control, and hybrid amplification, the system achieves higher spectral efficiency and improved scalability. It also delivers robust performance under diverse operating conditions. Collectively, these features highlight its potential as an effective solution for next-generation, high-bandwidth optical access systems. The system can adapt in real time to changing channel conditions, varying network loads, and operational disturbances.