The main challenge faced in today's telecommunication is the ever increasing demand for bandwidth and data rates. The desire to expand the capacity of fiber optic communication to accommodate this demand accelerated the development of high capacity Dense Wavelength Division Multiplexing (DWDM) transmission equipment. However, nonlinear impairments are the fundamental limiting mechanisms to the amount of data that can be transmitted in DWDM. In DWDM, Four Wave Mixing is the most critical of nonlinear effects in fibre optics communication. This effect limits the DWDM’s channel capacity. There are numerous researches on nonlinear impairments that show the intricacy of FWM phenomena in DWDM system. This article present review of the several measures which have been carried out by researchers to overcome nonlinear effects in DWDM. Such measures include Modulation Formats, Channel Spacing, Channel Shuffling Algorithm and Electro-Optic Phase Modulation. The review provides insight into the methods, parameters and approaches used by other researchers. This will pave way for can thus lead to significant improvement in the design of DWDM system.

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An essential feature of a long-haul Optical Communication System (OCS) is to transmit huge volumes of data over long distances. In OCS, fiber dispersion and Four-Wave Mixing (FWM) play negative roles in achieving this, as the propagation of the light signal, associated with the pulse, travels at varying speeds. Dense Wavelength Division Multiplexing (DWDM) system is not spared from these identified limitations.  In this work, a mathematical analysis for the dispersion and FWM was presented and validated through simulation software. The research was designed and implemented using an optical simulation software tool, OptiSystem 17.0. Transmission parameters of dispersion and Nonlinear (NL) effects due to refractive index, FWM, were considered.  The research was carried out on a 125 km-long fiber link and was investigated under a 16-channel DWDM system. The effects of identified limitations on the performance of the DWDM system with channel arrangement of 100, 50, and 25 GHz were further explored. This work compared the DWDM system under these different channel arrangements.  The transmission performance of the DWDM system was evaluated based on signal power, noise power, and eye pattern. The results obtained show that any increase in capacity causes significant decreases in the performance of the DWDM system. It was, however, noted that noise power is independent of an increase in bit rate. The results obtained further revealled that the launched power of the system must be reduced for better performance of the DWDM system and improved immunity against identified limitations.

Energy Harvesting (EH) is the process of capturing energy from external sources and storing it for small wireless autonomous devices. Radio Frequency (RF) EH aims at capturing ambient energy with an antenna and transforms this energy into exploitable power. Different energy fields are available in nature from which energy can be harvested. An impedance matching circuit for an RF energy harvester was designed in this paper. The design is made up of the antenna circuit which captures the RF signals from the mobile and Wi-Fi bands in the atmosphere, and the impedance network that matches between the RF source and the load to capture the power. A Villard voltage multiplier was employed to rectify and step up the captured RF signal into a useable direct current output voltage. Due to the low output voltage obtained after rectification, the voltage was boosted to the power needed for the load. The output of the boost converter was then used to charge a lithium-ion battery. In this paper, Intelligent Schematic Input System proteus professional suite software was used in simulating the designed system. This was used to analyze the performance of each system’s component and to evaluate the quality of the designed circuitry. RF energy harvesters convert electromagnetic waves into usable DC voltage. However, the harvested energy is relatively low to the required voltage. Different techniques have been proposed, but the complexity of energy harvesting persists. This discourages the use of low-power devices. Bridging this gap will improve energy harvesters’ efficiency.