A space division multiplexed free-space-optical communication system that can auto-locate and fully self align with a remote transceiver

Abstract

Free-Space Optical (FSO) systems offer the ability to distribute high speed digital links into remote and rural communities where terrain, installation cost or infrastructure security pose critical hurdles to deployment. A challenge in any point-to-point FSO system is initiating and maintaining optical alignment from the sender to the receiver. In this paper we propose and demonstrate a low-complexity self-aligning FSO prototype that can completely self-align with no requirement for initial manual positioning and could therefore form the opto-mechanical basis for a mesh network of optical transceivers. The prototype utilises off-the-shelf consumer electrical components and a bespoke alignment algorithm. We demonstrate an eight fibre spatially multiplexed link with a loss of 15 dB over 210 m.

Structured Light in Turbulence

“…Since beam wander and angle-of-arrival fluctuations are dominant in turbulence, a simple tip/tilt mirror can be used as a rudimentary adaptive optics system, ensuring that the received beam is always aligned onto the detector or detection hologram [235]. In addition, the receiver and / or transmitter can also be tilted to compensate for beam wander and pointing jitter [236]. Adaptive optics that also make use of deformable mirrors (used in astronomy) are very effective at correcting wavefront error introduced by turbulence, and work surprisingly well for OAM beams even though the systems are designed for Gaussian beams [237].…”

All-inorganic perovskite quantum dot light-emitting memories

“…Although the switching speed between two perovskite devices in the LEM is still slower than that of the state-of-the-art RRAM for performing data processing in series 51 , 52 , we expect that it could be further improved by optimizing our perovskite synthesis and the perovskite device structure (such as device dimension, geometry, and layer thickness). Apart from the optimization on the device level, by employing the LEM in a more complicated network structure such as multicast mesh network 53 , 54 , we envision that the overall transmitted data rate of the LEM could be further enhanced. In any case, the present demonstration on the fast operation and active switching of the all-perovskite LEM successfully sets a new benchmark for the development of more advanced LEM technologies.…”

Roadmap to free space optics

“…This allows the beam to be well collimated (or even focused) at the receiver, ensuring high SNR and thus high data rate. A further benefit of an active system, depending on its design, is the possibility of actively correcting turbulence-induced tip and tilt aberrations [57], [58]. An expanded beam is a cheap and simple solution but is unlikely to be feasible over long distances due to receiver sensitivity issues.…”