Development of Satellite Propagation Effects Tool For Ku-Band, Ka-Band And Q/V-Band Links

The thesis presents Graphical User Interfaces (GUIs) to analyse satellite propagation effects for Ku-band, Ka-band and QN-band links by using Matlab programming languages. The Matlab-based tool allows simulation to be carried out in the step and run modes. The Graphical User Interface (GUI) is a powerful, unique utility and programming interface, usable for research and simulation in the optimisation of microwave signal propagation. The GUIs gives easy access to analyse rain attenuation, cloud attenuation and fog attenuation. These software development tools are a set of Matlab solvers, graphical, computational utilities for quadratic, polynomial and regression programming. The GUIs may also be used as a preprocessor to generate Matlab code for stand-alone execution. Once the software tools for satellite propagation effects on Ku-band, Ka-band and QN-bands links GUIs is launched, user can enter input parameter values (frequency, elevation angle, temperature, visibility, cloud cover, rainfall, e.t.c) in text control to analyse the propagation impairments. In this thesis, the characteristics of the reliable design of satellite communication systems operating at frequency above 10 GHz, Ku (12.5 - 18 GHz), Ka (26.5 - 40GHz) and QN (40 - 50 GHz) band were examined. Rain attenuation, cloud attenuation and fog attenuation are the sources for fading propagation effects in these bands frequency. Analytical and ITU recommendations models were used to predict output attenuation for this analysis. However, the effects on satellite systems operating in the Ku, Ka and QN band essentially depends on the propagation characteristics of the transmission medium. The NOAA ((National Oceanic and Atmospheric Administration) satellite data 2003, which were obtained from the Malaysian Meteorological service, were used in this analysis for area of interest Subang (elevation angle 36.54'), Alor Setar (elevation angle 34.97'), and Batu Embun (elevation angle 37.25'). The rain attenuation due to rainfall depends on the rain rate (mrnlhr) distribution at the 0.01% probability as main the input. At the Ku, Ka and QN-bands frequencies, rain is a dominant source of attenuation. Thunderstorm activities were found to give large effect on the rain rate values during raining condition. Cloud attenuation is a function of cloud temperature integrated cloud liquid water content (g/m3) along propagation path. For fog attenuation, visibility and temperature become main meteorological input function along propagation path analysis at the earth station site. Cloud and fog attenuation, which have been neglected at the lower frequencies band, can significantly limit the performance of high frequencies band satellite systems. However, in recent years, higher frequencies are gradually being used for satellite communications in order to avoid congestion in the traditional low bands (S, L, C and X) frequencies and can be used for high quality satellite service. Unfortunately increasing operating frequency from Ku-band to Ka-band and QN-band will increase the attenuation level and hence, reducing performance of the satellite

Optimization of output coupling ratio on the performance of a ring-cavity Brillouin–erbium fiber laser

The operation of a single-wavelength Brillouin-erbium fiber laser (BEFL) system with a Brillouin pump preamplified technique for different output coupling ratios in a ring cavity is experimentally demonstrated. The characteristics of Brillouin Stokes power and tunability were investigated in this research. The efficiency of the BEFL operation was obtained at an optimum output coupling ratio of 95%. By fixing the Brillouin pump wavelength at 1550 nm while its power was set at 1.6 mW and the 1480 pump power was set to its maximum value of 135 mW, the Brillioun Stokes power was found to be 28.7 mW. The Stokes signal can be tuned within a range of 60 nm from 1520 to 1580 nm without appearances of the self-lasing cavity modes in the laser system

Multiwavelength Brillouin/ erbium fiber laser utilizing virtual reflectivity in dispersion compensating fiber

We proposed and experimentally demonstrate a novel scheme of Brillouin/erbium fiber laser (BEFL) in a ring cavity configuration. The Brillouin gain media, which is provided by a dispersion compensating fiber (DCF), was manipulated and used as virtual mirror .The laser structure that consists of only four optical components is simple, devoid of the complex structures employed previously to enhance the feedback mechanism normally associated with multiwavelength sources. Our structure can produce up to 4 stable channels at a low Brillouin pump power of -1 dBm and a 1480 nm pump power of 130 mW which are separated by 10 GHz (0.08 nm)

Single-wavelength ring-cavity fiber laser employed preamplification technique to reduce threshold by circulating spontaneous Brillouin scattering

In this paper, two types of ring-cavity fiber laser structures that operate as a single wavelength laser were investigated on the threshold performance. The two structures are namely Brillouin fiber laser and Brillouin erbium fiber laser. In the first structure, the Brillouin pump signal was amplified before being injected into the laser cavity which namely as Brillouin fiber laser. Meanwhile, for second structure respectively, the Brillouin pump signal was pre-amplified in the laser cavity which namely as Brillouin Erbium fiber laser. We found that the stimulated Brillouin scattering threshold power was lowered significantly by circulating the spontaneous Brillouin scattering in the gain medium utilizing the pre-amplification technique. The optimum stimulated Brillouin scattering threshold power was about 1.4 mW, and this was achieved at optimum output coupling ratio of 95%. By comparing to the first structure in which the Brillouin pump signal was amplified before entering the laser cavity, stimulated Brillouin scattering threshold power was only achieved at 2.62 mW at a similar wavelength. The pre-amplification technique proposed in this paper has been shown to improve the performance of single-wavelength ring-cavity fiber lasers via significant reduction of the stimulated Brillouin scattering threshold power which was around 1.22 mW

Single-wavelength ring-cavity Brillouin-Raman fiber laser

We experimentally demonstrate a ring-cavity, single-wavelength Brillouin-Raman fiber laser. An 11-km long dispersion compensating fiber was used as the medium for the Raman as well as the Brillouin amplification. A threshold power of 27 mW was recorded to get the Brillouin-Stokes line at 1455 nm pump wavelength. At an injected Brillouin pump power of 2 mW, while the Raman pump unit was fixed at a power of 296 mW, the single-wavelength Brillouin-Raman fiber laser can be tuned from 1520 nm to 1580 nm without any self-lasing cavity modes in the laser system. The Brillouin- Stokes line has a 3-dB power fluctuation within 26 nm from 1542 nm to 1568 nm

Effect of output coupling ratio on the performance of ring-cavity Brillouin fiber laser

We present a single-wavelength Brillouin fiber laser utilizing a ring-cavity configuration. Performances and characteristics of the laser system have been investigated at different output coupling ratios. The optimum output power of the system stood at 7.3 mW, which was obtained at 90% output coupling ratio. A low Brillouin threshold power of 0.9 mW was obtained at 10% output coupling ratio when the Brillouin pump was set at its maximum power of 24 mW

Multiwavelength Brillouin-Raman ring-cavity fiber laser with 22-GHz spacing.

We experimentally demonstrate a multi-wave length Brillouin-Raman fiber laser configured in a ring-cavity resonator. Interactions between stimulated Brillouin scattering and Raman amplification in a dispersion compensating fiber, attributed to the generation of 16 output channels at injected Raman pump unit power of 650 mW and Brillouin pump power of 2.0 mW. The first output channel has a peak power of 14.8 mW. By discriminating the even-order Brillouin Stokes signals from circulating in the resonator, the generated output channels were found to have wavelength spacing of ∼22 GHz. The output channels were also found to have average optical signal-to-noise ratio value of 11.7 dB

Amplitude equilibrium dual-wavelength fiber laser through Brillouin pump recycling technique

A simple structure for amplitude equilibrium dual-wavelength fiber laser is proposed and experimentally demonstrated. This structure is based on the Brillouin Stokes generation in a 6.7 km single mode optical fiber (SMF) spool. Counter-propagating Stokes is generated in the SMF as the injected Brillouin pump exceeds the threshold and the transmitted Brillouin pump signal at the other end of SMF is recycled to the SMF which acts as the Brillouin gain medium by an optical mirror. The reflected Brillouin pump amplifies the generated Stokes line and reduces the Brillouin pump threshold. With 12.44 mW Brillouin pump peak power, dual wavelength output peak power at -11.08 dBm and -11.16 dBm with 10.98 GHz spacing are obtained

Critical analysis of stability and performance of organometal halide perovskite solar cells via various fabrication method ( Review

Organometal halide perovskite solar cells (Omh-PSCs) have attracted attention due to its unique electrical and optical properties. Ideally, the Omh-PSCs should remain free from degradation under normal operating conditions for several years, preferably tens of years. In order to produce high power conversion efficiency with low potential of degradation, different fabrication methods have been developed. The reported stability of perovskite films can vary significantly and reported to decay substantially up to 20% of its original performance. A thorough understanding of fabrication process upon the stability of the device is regarded as crucial to pave the way for future endeavors. This review summarized and highlighted the recent research of fabrication methods that gave an impact to the stability of perovskite devices

Single-wavelength ring-cavity fiber laser with improved tunability based on nonlinear stimulated Brillouin scattering

Stimulated Brillouin scattering (SBS) is a nonlinear phenomenon that occurs in a optical fiber as a result of interaction between an injected coherent pump signal and an acoustic wave, resulting in backward propagating signal named Stokes wave. Practically for single-mode silica fiber (SMF), the Stokes wave was found to be downshifted by 0.08 nm (10 GHz) from the injected signal wavelength, through the Doppler effect. SBS generation has been considered generated a lot of interest for its deployment in a number of applications, such as microwave generation, frequency shifting, narrow-bandwidth amplification and fiber laser. This thesis focuses on the utilization of the nonlinear effects in dispersion compensating fiber (DCF),particularly the SBS to generate a single-wavelength laser in ring-cavity configurations. In this thesis, three types of fiber laser in ring-cavity configurations were investigated namely; Brillouin fiber laser (BFL), Brillouin Erbium fiber laser (BEFL), and Brillouin Raman fiber laser (BRFL). All the results presented in this thesis have been published. For ring cavity BFL, the lowest Brillouin threshold power of 0.9 mW, Brillouin signal (BS) peak power of 7.28 mW and the flatness of the BS power were obtained. The lasing wavelength of BFL structure can be tuned freely in the cavity because the laser structure does not produce any self-lasing cavity modes. The lasing wavelength is strictly dependent on the BP wavelength and subject to the availability of amplification bandwidth. The impact of Erbium-doped fiber amplifier (EDFA) location in the BEFL structure was investigated. A single-wavelength BEFL-1 structure in which the Brillouin pump (BP) is pre-amplified before entering the DCF produced 25.1 mW of BS signal power and tuning range of 50 nm. In contrast the BS signal power of 15.5 mW and 1.4 mW was obtained from BEFL-2 and BEFL-3, which can only be tuned over 28 nm and 3 nm respectively. In conclusion, the BEFL-1 generated higher gain efficiency to suppress the self-lasing-cavity modes in the cavity and provided higher BS signal power. Next, the characteristics of this BEFL structure in which the BP is pre-amplified before entering the DCF was demonstrated with variation of output coupling ratios from 10% to 99%. The highest BS signal power of 28.7 mW and wider tuning range over 60 nm without any self-lasing cavity modes were obtained. For the final experiment, the BRFL characteristics in terms of BS signal power,threshold power and tuning range were reported. The BS signal power of 2.71 mW,threshold power of 27 mW and BS signal power flatness of 26 nm were obtained. It is evidently shown that the BRFL can be operated freely without any appearance of the self-lasing cavity modes for all cases of the injected RPU power