Radio-over-fiber transport system employing free-space optical communication scheme with parabolic reflector

Historical perspective of free space optical communications: from the early dates to today's developments

“…In practical network design, the concept of link availability in the presence of atmospheric turbulence is an important consideration. In many FSO systems, automatic tracking systems are used so that pointing errors are not taken into account in defining link reliability [69]. As an example, for simplicity, if atmospheric turbulence is characterised by the log-normal model so that the PDF of the irradiance I can be characterised by…”

“…7. The RoFSO technology can also be deployed for the connection of centralpoint/base-station to multiple numbers of remote points by distributing microwave signals by means of optical signals [69]. Two physicists, Ludwig Mach and Ludwig Zehnder devised an apparatus called Mach-Zehnder modulator (MZM) which is used to perform the modulation of an optical beam as a function of a RF signal by combining phase-delayed optical beams of an optical source.…”

“…This principle, thereby, controls the amplitude and phase of the unmodulated incident optical carrier. The Pockels effect changes the refractive index of the optical medium, thus, the MZM can also be used for amplitude, phase and frequency modulations [69,70].…”

“…The combined, i.e. the modulated form of these two-phase shifted optical beams at the output is given by [69] E out t = 0.5E in t e jπ(E 1 (t)/V π ) + e jπ(E 2 (t)/…”

“…In the RoFSO system, calculation of power margin is necessary to estimate the losses associated with fading, SMF coupling, freespace beam geometry, and atmospheric attenuation. The fading loss can be calculated by [69][70][71] a scin = 4.343 erf −1 2p thr − 1 ⋅ 2ln σ p 2 + 1 − 1 2 ln σ p 2 + 1 (18) where p thr is the probability of outage time, erf −1 is the inverse error function and σ p 2 is the power scintillation index calculated by…”