Evaluation of Optical Communication Systems Performance in High Humidity Coastal Environments in Calabar, Cross River State

Background: Coastal cities such as Calabar in South South Nigeria experience persistently high atmospheric humidity that can degrade optical communication system components through corrosion, condensation, and moisture ingress. Systematic performance evaluation in this environment is needed. Aim: This study evaluated the performance of optical fibre and free-space optical communication systems in the high-humidity coastal environment of Calabar, Cross River State. Methods: Optical link attenuation, bit error rate, and connector reflectance were measured for fibre links and a 500-metre free-space optical link at the Cross River State Broadcasting Corporation over 12 months. Atmospheric transmittance was correlated with humidity and visibility data. Results: Free-space optical link attenuation increased by up to 38 dB/km during peak humidity and fog conditions, causing link outages in 11.2% of monitored hours. Fibre connector degradation added a mean 0.6 dB loss after 12 months of coastal exposure. Sealed IP68-rated connector housings showed negligible degradation. Conclusion: High humidity significantly degrades free-space optical links in coastal Nigeria, limiting their reliability for critical communications. Fibre systems with sealed connectors are recommended for coastal deployments. Keywords: optical communication, high humidity, coastal environment, Calabar, free-space optics.