تجزیه و تحلیل عملکرد پیشرفته از سیستم بین ماهواره ای ارتباطی نوری - بی سیم (IsOWC)

In this paper, we have reported the improved performance by usage of a square root module. By simulation in OPTISYSTEM™ a distance of 5000 km with 1.25 Gbps was achieved with the same performance representing an enhancement of 48% when compared to the traditional detection.

Inter satellite optical wireless communications (IsOWC) systems provide a high bandwidth, small size, light weight, low power and low cost alternative to present microwave satellite systems. The inter satellite optical communications systems will be deployed in space in the near future. The present satellite communications system uses microwave technology for space-to-ground and geosynchronous satellite to low earth orbiting vehicles or platforms. In this future system, the satellite to ground links would remain in the microwave regime. A secondary effort is the development of optical technology for future low earth orbiting (LEO) space communications. Satellites revolve around Earth at their own orbit and there are three commonly used orbits for satellites. Satellite orbits with orbital height of approximately 1000 km or less are known as Low Earth Orbit (LEO). Satellite orbits with orbital heights of typically in the range of 5000 km to about 25,000 km are known as Medium Earth Orbit (MEO). In Geosynchronous Earth Orbit (GEO) the satellite is in equatorial circular orbit with an altitude of 35,786 km and orbital period of 24 h. Three satellites in GEO placed 120° apart over equator cover most of the world for communications purposes [1]. At present there are 6124 satellites orbiting Earth and this number increases year by year [2]. At the same time, the optical wireless communication (OWC) technology has grown and advanced throughout the year. Laser communication is now able to send information at data rates up to several Gbps and at distance of thousands of kilometers apart. This has open up the idea to adapt optical wireless communication technology into space technology, hence IsOWC is developed. IsOWC can be used to connect one satellite to another, whether the satellite is in the same orbit or in different orbits. With light traveling at 3 × 108 m/s, data can be sent without much delay and with minimum attenuation since the space is considered to be vacuum. The advantages of using optical link over radio frequency (RF) links is the ability to send high speed data to a distance of thousands of kilometers using small size payload [3]. By reducing the size of the payload, the mass and the cost of the satellite will also be decreases. Another reason of using optical wireless communications is due to wavelength. RF wavelength is much longer compared to lasers hence the beam width that can be achieved using lasers is narrower than that of the RF system [4]. Due to this reason, Optical wireless communications link results in lower loss compared to RF but it requires a highly accurate tracking system to make sure that the connecting satellites are aligned and have line of sight. In IsOWC different parameter play an important role, one of them is pointing errors. The pointing errors can arise due to mechanical misalignment, errors in tracking systems, or due to mechanical vibrations present in the system. Pointing errors can be thought of being composed of two components: a fixed error, called bore sight, and a random error, called jitter. The behaviors of pointing errors and related issues are treated in [5], where the irradiance probability density function due to bore sight and jitter has been derived. Scintillation is the temporal and spatial variations in light intensity caused by atmospheric turbulence. Such turbulence is caused by wind and temperature gradients that create pockets of air with rapidly varying densities and therefore fast-changing indices of optical refraction [6]. Here [7] presented the IsOWC link performance on data transfer between Low Earth Orbit satellites. The system performance including bit rates, input power, wavelength and distance on an inter-satellite link were also analyzed. This paper focused [8] on effect of satellite vibration on various parameters like pointing angle, received signal power and hence the BER of the system are studied. Additional losses like Geometrical loss etc. It is a loss that occurs due to the spreading of the transmitted beam between the transmitter and the receiver [9]. It is dependent on beam divergence, elevation angle, diameter of receiver capture surface as well as link distance. Here [10] reported the improved investigation through implementation of a square root module using OPTISYSTEM™ simulator to establish an inter-satellite link (ISL) between two satellites estranged by a distance of 1000 km at data rate of 2.5 Gbps for LEO. In this work, we have presented the simulation investigation of Inter satellite optical wireless communication systems for long distance. The paper is organized as follows: Section 2 contains the system description. Section 3 discusses the results of Inter satellite optical wireless communications system. Finally, Section 4 summarizes and concludes this paper.

In this paper work, we have designed an inter-satellite optical-wireless communication system with- and without-SR module and presented analysis of inter-satellite optical-wireless communication system with different parameters and reported the improved investigation through implementation of a square root module using OPTISYSTEM™ simulator by a distance of 5000 km with BER 10−7 at data rate of 1.25 Gbps. Hence through square root module an efficient improvement in inter-satellite optical-wireless communication system is achieved, which further helps in increasing the transmission length of the system