Obtaining diffraction limited astronomical images using ground-based telescopes and sensors operating at optical wavelengths is currently not possible due to the effects of atmospheric turbulence. Adaptive optics is a mature technology that attempts to minimise the effects of atmospheric turbulence through wavefront detection and optical path correction in real-time. Our work involves the acqui...

In a free-space optical communication system employing fiber-optic components, the phasefront distortions induced by atmospheric turbulence limit the efficiency with which the laser beam is coupled into a single-mode fiber. We analyze different link scenarios including a geostationary (GEO) satellite, a high-altitude platform (HAP), and an optical ground station (OGS). Singlemode coupled optica...

We describe a coded power-efficient transmission scheme based on repetition MIMO principle suitable for communication over the atmospheric turbulence channel, and determine its channel capacity. The proposed scheme employs the Q-ary pulse-position modulation. We further study how to approach the channel capacity limits using low-density parity-check (LDPC) codes. Component LDPC codes are design...

In this paper we analyze multiple-input multiple-output (MIMO) free-space optical (FSO) communication systems with Q-ary pulse position modulation (PPM) and avalanche photodiodes (APDs) in the receiver array in the presence of atmospheric turbulence, and derive the general maximum-likelihood (ML) detection rule and the Chernoff bound on error probability (Pe) for the MIMO setup. The obtained an...

In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of received light signal, impairing link performance. In this paper, we describe several communication techniques to mitigate turbulence-induced intensity fluctuations, that is signal fading. These techniques are applicable in the regime in which the receiver aperture is sma...

Atmospheric turbulence causes most weather-related aircraft incidents. Commercial aircraft encounter moderate-or-greater turbulence tens of thousands of times each year worldwide, injuring probably hundreds of passengers (occasionally fatally), costing airlines tens of millions of dollars and causing structural damage to planes. Clear-air turbulence is especially difficult to avoid, because it ...

Free-space optical (FSO) communications using intensity modulation and direct detection (IM/DD), is a cost-effective and high bandwidth access technique, which has recently received significant attention and commercial interest for a variety of applications [30, 44]. Optical wireless communication systems are rapidly gaining popularity as effective means of transferring data at high rates over ...

This study studies the performance of multihop free-space optical systems using the subcarrier binary phase-shift keying modulation over atmospheric turbulence channels. The authors propose a modified relaying strategy, termed ‘amplify– decode-and-forward’, realised by using avalanche photodiode (APD) receivers. The outage probability of the proposed system is analytically derived considering t...

This paper studies the performance of multihop free-space optical (FSO) systems using the subcarrier binary phase-shift keying modulation (BPSK) over atmospheric turbulence channels. We propose a modified relaying strategy, termed amplify-decode-and-forward (ADF), realised by using avalanche photodiode (APD) receivers. The outage probability of the proposed system is analytically derived consid...

The wind farm program FLaP (Farm Layout Program), developed at the University of Oldenburg, has been extended to improve the description of wake development in offshore conditions. Especially the low ambient turbulence and the effect of atmospheric stability have been addressed. Model results have been compared with measured vertical wake profiles and mean turbulence intensities from the Danish...