Quantum structures (e.g. quantum wells) are a critical part of optical system designs (lasers, modulators, switches etc.). In the quantum well, the motion of the particle is quantized in one direction while the particle moves freely in other two directions. The density of state of the quantum structure is the possible number of state an excited electron can occupy per unit volume. The density of state depends on the energy at which the electron moves when excited. In this paper, the energy and density of states of two-dimensional quantum structure (quantum well) were calculated. The results obtained revealed the density of state increases with the energy but exhibited maximum and minimum peaks. Maximum peaks occurred at 4 eV and 7.5 eV while the minimum peaks occurred at 5 eV and 8 eV. These show that energy of state for quantum wells neither varies linearly nor exponentially with a density of state because of high energy level. The findings are in agreement with published literature. Some applications of quantum wells include: bioconjugates, solar cells, photovoltaic, photo and electrochromic devices etc.
Attenuation is an undesirable factor that weakens the strength of signal as it travels down fiber optics. Attenuation level in every fiber communication link must be kept at its tolerable range in order to maintain good signal transmission. When the level of attenuation in a link is higher than the acceptable tolerance value, the transmission suffers some setbacks such as loss of signal, freezing of signal etc. An optoelectronic device, Optical Time Domain Reflectometer (OTDR) was used in the measurement of attenuations in the single-mode fiber using the uni-directional technique. It is a convenient and powerful tool for rapidly assessing attenuation behavior in optical fibers. It combines a detector and laser source to provide an inside view of the fiber link described by a trace. The injected light pulse from the laser source is received at the detector. OTDR traces were produced in accordance with the light pulses received. From these traces, the attenuation levels for the different fiber cores were obtained. An average attenuation limit of 0.188 dB/km and average section loss of 0.3dB for 1550 nm wavelength window over the span length of 1597.35 m were achieved which are within the acceptable standard range of 0.20 dB/km to 0.30 dB/km.
This paper presents the design and implementation of dual-stacked identical Yagi antenna. An Antenna is an essential terminal device in all forms of communication and radar systems. Without an antenna there would be neither communication system nor radar system. An antenna acts as a source as well as a sensor of electromagnetic waves. The design was done using an online Yagi calculator software (AN SOF Antenna Simulator) which calculated the length, diameter, and the spacing of the materials (elements and boom) used in the construction. The Yagi antenna implementation was carried out using a cutting machine in cutting off various lengths of the elements specified by the Yagi calculator software. the elements were arranged on the aluminum boom and the coaxial cable impedances and dipole element were matched. The identical Yagi antennas were stacked (1020 mm center to center spacing)vertically leading to an increase in gain of 15.4 dBwhen compared with 12.7 dBgain obtainable from a single Yagi antenna and larger capture area (effective aperture).This design was able to solve the problems of underground noise, interference, low picture quality, low gain, and large beamwidth associated with a single Yagi antenna. This antenna can be used for UHF (300-3000 MHz) applications.
An optical fiber link is a part of an optic fiber communication system. Other components of the optic fiber link include the transmitter, connectors, and the receiver. The optical fiber could be single mode (for long distance transmission) or multi (for short distance transmission). This paper however, majors on the impact of reflectance in the single optical fiber. Reflectance is a hidden threat that increases Bit Error Rate, BER, (rate at which errors occur in transmission system) and reduces sy performance if not monitored or controlled. Optical Time Domain Reflectometer (OTDR) was used to measure the reflectance in single-mode fiber. Events measurements in OTDR heavily depend on good reflectance. The OTDR was able to establish the reflectance in every portion of the fiber under test. An average reflectance level of -14.9275 dB of 1550 nm signal over the span length of 20.422 km was achieved which is within the acceptable standard range. Hence, good quality performance transmissions can be achieved along these routes.
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