On the derivation of exact analytical FSO link attenuation model

Abstract

The development of semiconductor technology has led to an increase of the usable bandwidth of light-emitting diodes (LED), which are suitable for indoor high-speed communications or free-space optical (FSO) communications over a relatively short distance. The high-speed long-distance FSO links, where turbulence effects are considerably high, are a domain of laser sources. Hence, the paper covers the study of an exact analytical model of FSO link attenuation and the benefits of using an elliptically symmetrical Gaussian beam rather than a circularly symmetrical one.The paper further generalises the study to the FSO link misalignment and the pointing error analysis. The main contribution is in the derivation of an exact laser beam attenuation model, which is further used to analyse the geometrical losses in FSO systems as well as a general misalignment of an elliptically symmetrical beam in any direction from a circular receiver aperture. The challenging mathematical part includes two and six expressions of the general laser beam attenuation model for FSO communications taking into consideration circular and elliptical beams, respectively. The paper concludes with an analysis of advantages of using elliptical beams in FSO systems and a discussion on optimal orientation of the major beam axis with respect to the maximisation of the link availability.The paper summarises some previous results of the team of authors to further extend the model's applicability into more general terms towards a unified model.

A Tb/s Indoor Optical Wireless Backhaul System Using VCSEL Arrays

“…By combining (13), (17), (18) and (20), the DC gain of the channel, denoted by H 0 (φ a , φ e , ψ a , ψ e ), can be evaluated based on (7) and (22) when using:…”

“…By contrast, in [18], Huang and Safari, through applying a small angle approximation, have modeled the receiver-induced angle-of-arrival (AOA) misalignment again as a radial displacement of the optical field pattern on the photodetector (PD) plane. In [19], [20], Poliak et al have presented a link budget model for FSO systems in an effort to incorporate misalignment losses for Gaussian beams individually, including lateral displacement, tilt of the transmitter and tilt of the receiver. Nonetheless, the effect of these tilt angles has been simplified by a lateral displacement.…”

Relay selection in mixed RF/FSO system over generalized channel fading

“…The cdf of the equivalent end-to-end SNR (F eq i ) of a single S R i D link for semi-blind relaying can be obtained using (15) as…”

“…0, D m) and Rician ( D 1). Further for the FSO link gg distribution affected by path losses and pointing errors is used to model weak to strong atmospheric turbulence fading for the FSO link [15,16]. It has simpler statistical characteristics and provide a good agreement between the experimental data and the theoretical result [17].…”

A Tb/s Indoor MIMO Optical Wireless Backhaul System Using VCSEL Arrays

“…By contrast, in [20], Huang and Safari, through applying a small angle approximation, have modeled the receiver-induced angle-of-arrival (AOA) misalignment again as a radial displacement of the optical field pattern on the photodetector (PD) plane. In [21], [22], Poliak et al have presented a link budget model for FSO systems in an effort to incorporate misalignment losses for Gaussian beams individually, including lateral displacement, tilt of the transmitter and tilt of the receiver. Nonetheless, the effect of these tilt angles has been simplified by a lateral displacement.…”