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To achieve multi-Gb/s data rates in 6G optical wireless access networks based on narrow infrared (IR) laser beams, a high-speed receiver with two key specifications is needed: a sufficiently large aperture to collect the required optical power and a wide field-of-view (FOV) to avoid strict alignment issues. This paper puts forward the systematic design and optimisation of multi-tier non-imaging angle diversity receivers (ADRs) composed of compound parabolic concentrators (CPCs) coupled with photodiode (PD) arrays for laser-based optical wireless communication (OWC) links. Design tradeoffs include the gain-FOV tradeoff for each receiver element and the area-bandwidth tradeoff for each PD array. The rate maximisation is formulated as a non-convex optimisation problem under the constraints on the minimum required FOV and the overall ADR dimensions to find the optimum configuration of the receiver bandwidth and FOV, and a low-complexity optimal solution is proposed. The ADR performance is studied using computer simulations and insightful design guidelines are provided through various numerical examples. An efficient technique is also proposed to reduce the ADR dimensions based on CPC length truncation. It is shown that a compact ADR with a height of $\leq 0.5$ cm and an effective area of $\leq 0.5$ cm2 reaches a data rate of 12 Gb/s with a half-angle FOV of 30° over a 3 m link distance.

Silicon Photomultipliers (SiPMs) can provide optical wireless communication (OWC) receivers with better sensitivities than PIN photodiodes, thanks to their photon counting capabilities. The commercial availability of SiPM with fast output pulse width allows high-speed data transmission at low irradiance levels. This article investigates the use of a commercially available SiPM with an active area of 1 mm2 and fast output pulse width of 0.6 ns in a Near-infrared (NIR) OWC link and compares the performance of a 3 mm x 3 mm SiPM with a fast output pulse width of 1.4 ns. Although both SiPMs have maximum detection efficiency at 450 nm, a wavelength of 850 nm is used owing to the availability of high-speed VCSELs, higher eye safety limit and ability to filter ambient light when using this wavelength. The OWC link is designed and tested at a 35 cm transmission distance using On-Off-Keying (OOK) and Decision Feedback Equalization (DFE), and a maximum data rate of 8.2 Gbps at a BER of 3.8 × 10−3 was obtained with 15.34 W/m2 irradiance at the SiPM. These results are achieved in the dark and under 500 lux of White Light Emitting Diode (WLED) ambient light. A long pass colour glass filter is used to reject light up to 700 nm wavelength, thus rejecting most of the interference from WLEDs, resulting in data rates similar to dark environments. This is the highest data rate achieved using SiPMs in an NIR link.

The quasi-static nature of the optical wireless channel means that the channel state information (CSI) can be readily available at the transmitter and receiver prior to data transmission. This implies that electrically band-limited optical wireless communication (OWC) systems can make use of optimal channel partitioning or vector coding based multi-channel modulation (MCM) to achieve high throughput by mitigating the non-linearities arising from the optical and electrical channel. This paper proposes a pulse amplitude modulation (PAM) based DC-biased optical vector coding (DCO-VC) MCM scheme for OWC. The throughput performance of DCO-VC is evaluated and compared to the well known DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) over hybrid (line-of-sight and diffuse) and diffuse (non line-of-sight only) visible light communication (VLC) channels with additive white Gaussian noise. For the completeness of the VLC physical layer, the performance comparison is based on an uncoded and a forward error correction transmission mode using well-known convolutional codes with Viterbi decoder. The results show that the coded DCO-VC outperforms DCO-OFDM system by achieving up to 2 and 3 dB signal to noise ratio gains over hybrid and diffuse VLC channels, respectively.

Light-emitting diodes (LEDs) are ubiquitous in modern society, with applications spanning from lighting and displays to medical diagnostics and data communications. Metal-halide perovskites are promising materials for LEDs because of their excellent optoelectronic properties and solution processability. Although research has progressed substantially in optimizing their external quantum efficiency, the modulation characteristics of perovskite LEDs remain unclear. Here we report a holistic approach for realizing fast perovskite photonic sources on silicon based on tailoring alkylammonium cations in perovskite systems. We reveal the recombination behaviour of charged species at various carrier density regimes relevant for their modulation performance. By integrating a Fabry–Pérot microcavity on silicon, we demonstrate perovskite devices with efficient light outcoupling. We achieve device modulation bandwidths of up to 42.6 MHz and data rates above 50 Mbps, with further analysis suggesting that the bandwidth may exceed gigahertz levels. The principles developed here will support the development of perovskite light sources for next-generation data-communication architectures. The demonstration of solution-processed perovskite emitters on silicon substrates also opens up the possibility of integration with micro-electronics platforms.

The design of a compact high-speed and wide field of view (FOV) receiver is challenging due to the presence of two well-known trade-offs. The first one is the area-bandwidth trade-off of photodetectors (PDs) and the second one is the gain-FOV trade-off due to the use of optics. The combined effects of these two trade-offs imply that the achievable data rate of an imaging optical receiver is limited by its FOV, i.e., a rate-FOV trade-off. In this paper, we propose an imaging receiver design in the form of an array of (PD) arrays. To control the area-bandwidth trade-off, small PDs are used in an array of arrays structure instead of a single large PD. Moreover, to achieve a reasonable receiver FOV, we use an array of focusing lenses that focus the light individually on each inner PD array. The proposed array of arrays structure provides an effective method to control both gain-FOV trade-off (via an array of lenses) and area-bandwidth trade-off (via arrays of small PDs). We first derive a tractable analytical model for the signal-to-noise ratio (SNR) of an array of PDs that is equipped with a focusing lens assuming maximum ratio combining (MRC). Then, we extend the model to the proposed array of arrays structure and the accuracy of the analytical model is verified based on several Optic Studio-based simulations. Next, we formulate an optimization problem to maximize the achievable data rate of the imaging receiver subject to a minimum required FOV. The optimization problem is solved for two commonly used modulation techniques, namely, on-off keying (OOK) and direct current (DC) biased optical orthogonal frequency division multiplexing (DCO-OFDM) with variable rate quadrature amplitude modulation (QAM). Our results show the limits of high speed wide-FOV imaging receivers that can support mobility. For example, it is demonstrated that a data rate of $\sim 24$ Gbps with a FOV of 15° is achievable using OOK with a total receiver size of 2 cm $\!\times \!\,\,2$ cm.

Theoretical and experimental work to integrate parabolic intracavity lens into a high-power tapered ridge-waveguide semiconductor laser diode is carried out. A finite difference beam propagation model is used to simulate the laser operation with and without the lens. Focused ion-beam etching is used to integrate the lens with the laser cavity. The lens is designed to compensate for the phase curvature of the incident mode on the output facet. This leads to improved linearity in the light-current characteristics of the device, showing an increase of up to 47 in power slope efficiency, 2-m broadening in near field pattern, and 1-deg narrowing in the far-field pattern. © 2003 Society of Photo-Optical Instrumentation Engineers.