Experimental Evaluation of PMD Effects in NRZ and QAM-modulated High-speed Optical Systems in Abuja, Nigeria

This study presents an experimental evaluation of Polarization Mode Dispersion (PMD) effects on high-speed optical communication systems in Abuja, Nigeria, using Non-Return-to-Zero (NRZ) and Quadrature Amplitude Modulation (QAM) formats over single-mode fiber. Tests were conducted across fiber lengths ranging from 1 km to 40 km, with signal bit rates between 15 Gbps and 240 Gbps, under varying environmental conditions, including temperatures of 28°C to 30°C and humidity levels up to 90%. Key performance metrics such as Bit Error Rate (BER), Differential Group Delay (DGD), timing jitter, output optical power, and eye diagram clarity were analyzed. Results show that BER increased from 1.2 × 10⁻⁶ to 6.8 × 10⁻⁴ for NRZ and from 2.3 × 10⁻⁵ to 9.2 × 10⁻³ for QAM as fiber length increased. Similarly, DGD rose from 3.2 ps at 1 km to 19.8 ps at 40 km, with NRZ showing more pronounced spikes. Jitter increased from 6.1 ps to 24.3 ps in NRZ and from 9.4 ps to 34.2 ps in QAM. Eye diagram analysis confirmed greater eye closure in QAM at shorter distances, indicating its heightened sensitivity to PMD. Additionally, increased temperature and humidity led to a 30% rise in BER, confirming the influence of environmental factors on PMD behavior. The study concludes that while both NRZ and QAM suffer performance degradation due to PMD, QAM is more severely impacted, emphasizing the need for modulation-specific PMD compensation strategies in long-haul, high-speed optical systems.