A survey on performance enhancement in free space optical communication system through channel models and modulation tec
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A survey on performance enhancement in free space optical communication system through channel models and modulation techniques D. Anandkumar1 · R. G. Sangeetha1 Received: 17 March 2020 / Accepted: 8 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Free space optical (FSO) communication system has obtained significant importance in communication field due to its unique features: unlimited spectrum, larger bandwidth and high data rate, low mass and less power requirements, quick and easy deployability. FSO system better suits in disaster recovery, defense and last mile problems in networks, remote sensing and so on. However, FSO system has greater advantage, its performance is mainly degraded by adverse effects like beam wandering and spreading, scattering and mainly a major degradation factor is atmospheric turbulence and pointing errors which leads to severe degradation in Bit error rate (BER) and Signal to noise ratio (SNR) of the FSO link and makes the communication link infeasible. This paper gives a detailed survey on performance enhancement of FSO communication system and also discusses various channel distribution models and modulation techniques to have high reliability and FSO link availability. In this paper, the various atmospheric effects like turbulence, fog, absorption and scintillation and so on are discussed. The first part of the paper analysis the channel models and the latter part of the paper summarizes the different modulation techniques, diversity techniques and also the comparative study of the (SNR) and (BER) under various atmospheric factors of the FSO system. This survey provides the comprehensive details in order to provide low cost and high capacity FSO link design. Keywords Bit error rate · Distribution models · MIMO · Free space optics · Signal to noise ratio · Atmospheric turbulence · Pointing errors · Laser emitting diode
* R. G. Sangeetha [email protected] D. Anandkumar [email protected] 1
School of Electronics Engineering, VIT University, Chennai campus, Chennai, India
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D. Anandkumar, R. G. Sangeetha
1 Introduction The Free Space Optics (FSO) is a matured technology, which utilizes remote medium to transmit information electromagnetically for longer range (3–7 km) (Boucouvalas 2005; Willebrand and Ghuman 2002a). FSO encourages optical transmission rate of about 2.5–10 Gbps of date, voice and video information that permits without spectrum licenses and other advantages include large bandwidth, high security and less power consumption which extends FSO usage in large applications (Chadha 2013). FSO systems are of two types: indoor and outdoor FSO. Indoor FSO works in near Infra Red wavelength range (780–950 nm) and the outdoor FSO works in wavelength of 1550 nm Chadha (2013). The FSO system is subdivided into three parts: Transmitter, Channel link and the Receiver (Chadha 2013) as indicated in Fig. 1.
1.1 Transmitter The driver circuit is used by transmitter to convert elect
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