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Silicone rubber is one of the most used outdoor insulation materials in the last few decades due to its improved performance in contaminated and humid conditions. The improved performance of silicone rubber insulators is due to their hydrophobic nature however, the organic nature of silicone molecules makes them vulnerable to ageing and degradation. This paper aims at investigating the loss and recovery of hydrophobicity of four different silicone rubber micro/nanocomposites exposed to corona discharge. The samples were exposed to corona discharge generated by pin-plate electrode configuration under AC stress. A series of tests were performed to observe the impact of different electrode-sample gaps and for various periods of corona exposure. The hydrophobicity of samples was measured pre and post corona exposures at various intervals up to 72 hours. This time could confirm the hydrophobicity recovery process. Numerical simulations were also performed in COMSOL Multiphysics to investigate the electric fields along the sample surface at different electrode gaps. Experimental results showed that samples recovery time was proportional to the duration of exposure to corona discharge and inversely proportional to the electrode-sample gap. Among all, samples with 2.5% nano-silica as additive showed better hydrophobicity recovery. Simulation results showed that an increase in electrode gap resulted in decreased electric field intensity, hence supporting the experimental outcomes.

Free space optical (FSO) communication has gained significant popularity in recent years due to large bandwidth, license‐free spectrum, high data rates, less power consumption, and low mass requirements. However, system performance strongly depends on atmospheric conditions and ambient noise. In this letter, the duobinary modulation technique is applied and the system performance is investigated in the presence of ambient noise. The system is evaluated on the basis of Q‐factor, eye diagram, input power, transmission distance, and bit error rate. A significant improvement is observed in the presence of noise while using duobinary modulation. This study exploits extensive simulations to investigate the performance of the system. All simulations are performed for a single link of FSO communication network having a data rate of 40 Gbps in the Optisystem simulator and ambient noise is created using LEDs. After the exhaustive set of simulations, a significant improvement in transmission length is observed. It is also observed that at low input power, doubinary modulation provides better results when compared with on‐off keying (OOK) format. Scintillation effect has also be observed for doubinary modulation and compared with OOK modulation format. It is concluded that doubinary modulation provides better results in the presence of low and moderate scintillation.