Analysis of dispersion effect on a NRZ-OOK terrestrial free-space optical transmission system

Abstract

Background: In this paper, the impact of the dispersion effect, due to atmospheric pressure and temperature, on NRZ-OOK terrestrial free-space optical transmission system is investigated. An expression for the dispersion parameter in FSO atmospheric channel is derived. Results: The results show that the variation of the refractive index along the transmission path induces fluctuations of group velocity dispersion of the optical pulse resulting in broadening of the pulse duration. Simulation results show that at a propagation distance of 7.5 km, the broadening ratio for input pulse duration of 300 fs is approximately 2.39. Further, at a propagation distance of 7.5 km, the remaining fraction of energy is approximately 40 % for a 300 fs input pulse duration. However, by increasing the transmitter input power, the effect of dispersion could be reduced. Namely, for a reference BER of 10 -9 , the maximum distance that it could be achieved is about 1. 461 km for an input power of 1 mW, while it is about 2.694 km for an input power of 4 mW. Conclusions:The results indicate that the effect of dispersion resulting from pressure and temperature increases with the propagation distance, which induces a high BER. However, the results show that it is possible to reach longer propagation distances with a lower BER by increasing the input power.

Experimental and Analytical Investigations of an Optically Pre-Amplified FSO-MIMO System With Repetition Coding Over Non-Identically Distributed Correlated Channels

“…In this paper, we consider OOK IM/DD non-identical FSO links over the arbitrarily correlated AT channel in the presence of ASE noise. Note that, in order to study a practical system, we have assumed that the number of line-of-sight photons (non-dispersed) is sufficiently higher than the number of the scattered photons at the Rx and the transmit power is sufficient to reduce the effect of dispersion [28], [29]. Therefore, both the AT and spatial correlation are considered as the dominant factors affecting the performance of the proposed FSO system.…”

“…Finally, the average BER of the correlated FSO-MIMO system with RC in the presence of ASE noise can be obtained using P e = 1/2(P (1) e + P (2) e ) by substituting (26) and (29) in (24).…”

“…• The BER expression derived for the considered system with pre-amplifier is quite simple and can be easily implemented, since (26) consists of only finite weighted summations and the power series in (29) converge very fast at k, n ≈ 8−10. The Cauchy ratio test [38], [44] can be adopted to prove the convergence of the power series in (29).…”

“…It is not possible to get any intuition of the diversity order of the system from (16), (26), and (29). Therefore, for a better understanding of the system's performance behaviour, the asymptotic BER analysis at high SNR is performed in this section.…”

“…As mentioned in Section III-B.3, the BER expression of FSO-MIMO system with EDFA is obtained from (26) and (29) using P e = 1/2(P…”