In this study, a construction analysis and design of a new spreading code set are presented. This code is designed to be used as a source code in optical wireless communication (OWC) system to achieve better performance and security enhancement. The new proposed code is called double length modified prime code (DLMPC), which is constructed based on the popular modified prime code that is commonly applied in the optical code division multiple access (OCDMA) networks. The correlation properties and characteristics of the DLMPC are investigated in this study. Based on the new code, the OWC system architecture and channel model are illustrated and further analysed. Additionally, the transmitted and received data bits encoding and decoding scenarios are discussed. Moreover, a low power consumption optical light source and photo‐detector are utilised for a transmitter and receiver, respectively. The overall OWC performance in terms of the bit error rate (BER) has been evaluated considering the multi‐user interference as the only source of noise. Finally, the results show that the proposed DLMPC outperforms the popular codes with respect to the channel capacity, security, and system BER performance.

The bit error rate (BER) performance of the incoherent synchronous pulse position modulation optical code division multiple access (PPM-OCDMA) network has been analyzed using a multilength weighted modified prime code (ML-WMPC) for three different multimedia services, such as data, voice, and video. Each service has a different bit rate than the other services and, hence, a different WMPC code length. In the network performance calculations, the multiple access interference (MAI) is included and considered as the only source of noise. In addition, to improve the network performance, the Manchester encoding and the MAI cancellation techniques are used with the WMPC at a higher number of active users. The network performance calculations are introduced in terms of BER for three kinds of PPM-OCDMA receivers, such as a simple receiver, receiver with MAI cancellation (MAIC), and receiver with MAIC and Manchester encoding technique. Finally, the BER calculation has been investigated at different bit rate according to the type of service provided by the network in the presence of the ML-WMPC and the third PPM-OCDMA receiver.

In this paper, a nano solar cell structure based on a two-dimensional photonic crystal (2D-PhC) antireflection coating (ARC) trapping layer and a 2D- graded-index (2D-GI) GaAs active layer is presented. These components improve the solar absorption, in-coupling efficiency, quantum efficiency, and optical properties of the active layer. The proposed cell absorption and conversion efficiency were analyzed as a function of the cell layer thickness in comparison with the Lambertian absorption and cell efficiency limits. Additionally, each layer thickness was optimized to enhance the overall solar efficiency. All simulations were conducted in the 300 to 1100 nm range using finite difference time domain (FDTD) analysis, where the 2D-PhC structure was represented by indium tin oxide (ITO) nanorods in an air background. In addition, p-Al(0.85)GaAs/n-Al(0.35)GaAs two-window confinement layers are utilized in contact with the 907-nm GaAs active layer as a perfect match with the 1840-nm ITO-ARC layer to improve the confinement efficiency. Moreover, p-Al(0.85)GaAs/GaAs and GaAs/n-Al(0.35)GaAs 2D-GI active layer structures are used for index modulation to enhance the active layer properties and increase the cell short-circuit current. The main objective of this study is to determine the optimum design of a solar cell that can provide the highest power conversion efficiency using inexpensive semiconductor materials. One of the expected results from this research is the design of a 100- $\mu \text{m}^{2}$ nano solar cell with 39.2% conversion efficiency, a short circuit current density of 44.38 mA/cm ² , and an open-circuit voltage of 1 V.