Phosphorous Diffuser Diverged Blue Laser Diode for Indoor Lighting and Communication.

An advanced light-fidelity (Li-Fi) system based on the blue Gallium nitride (GaN) laser diode (LD) with a compact white-light phosphorous diffuser is demonstrated for fusing the indoor white-lighting and visible light communication (VLC). The phosphorous diffuser adhered blue GaN LD broadens luminescent spectrum and diverges beam spot to provide ample functionality including the completeness of Li-Fi feature and the quality of white-lighting. The phosphorous diffuser diverged white-light spot covers a radiant angle up to 120(o) with CIE coordinates of (0.34, 0.37). On the other hand, the degradation on throughput frequency response of the blue LD is mainly attributed to the self-feedback caused by the reflection from the phosphor-air interface. It represents the current state-of-the-art performance on carrying 5.2-Gbit/s orthogonal frequency-division multiplexed 16-quadrature-amplitude modulation (16-QAM OFDM) data with a bit error rate (BER) of 3.1 × 10(-3) over a 60-cm free-space link. This work aims to explore the plausibility of the phosphorous diffuser diverged blue GaN LD for future hybrid white-lighting and VLC systems

A review of gallium nitride LEDs for multi-gigabit-per-second visible light data communications

The field of visible light communications (VLC) has gained significant interest over the last decade, in both fibre and free-space embodiments. In fibre systems, the availability of low cost plastic optical fibre (POF) that is compatible with visible data communications has been a key enabler. In free-space applications, the availability of hundreds of THz of the unregulated spectrum makes VLC attractive for wireless communications. This paper provides an overview of the recent developments in VLC systems based on gallium nitride (GaN) light-emitting diodes (LEDs), covering aspects from sources to systems. The state-of-the-art technology enabling bandwidth of GaN LEDs in the range of >400 MHz is explored. Furthermore, advances in key technologies, including advanced modulation, equalisation, and multiplexing that have enabled free-space VLC data rates beyond 10 Gb/s are also outlined

10 Gbps Mobile Visible Light Communication System Employing Angle Diversity, Imaging Receivers, and Relay Nodes

Over the last decade, visible light communication (VLC) systems have typically operated between 50 Mbps and 3.4 Gbps. In this paper, we propose and evaluate mobile VLC systems that operate at 10 Gbps. The enhancements in channel bandwidth and data rate are achieved by the introduction of laser diodes (LDs), angle diversity receivers (ADR), imaging receivers, relay nodes and delay adaptation techniques. We propose three mobile VLC systems; an ADR relay assisted LD-VLC (ADRR-LD), an imaging relay assisted LD-VLC (IMGR-LD) and select-the-best imaging relay assisted LD-VLC (SBIMGR-LD). The ADR and imaging receiver are proposed for the VLC system to mitigate the intersymbol interference (ISI), maximise the signal to noise ratio (SNR) and reduce the impact of multipath dispersion due to mobility. The combination of IMGR-LD with a delay adaptation technique adds a degree of freedom to the link design, which results in a VLC system that has the ability to provide high data rates under mobility. The proposed IMGR-LD system achieves significant improvements in the SNR over other systems in the worst case scenario in the considered real indoor environment

Multifunction LED Lighting System Combining Tunable Spectrum and Data Communication

A comparison of two different lighting systems combining tunable illumination, visible light communications (VLC) and sensing capabilities. The first method is based on light emitting diodes (LED) as light source and multifunction smart sensors and the second one with LEDs and micro-spectrometer to be included in the transceiver and/or receiver. Both systems are intended for future lighting sensor networks that combine standardized optical communications according the standard IEEE802.15.7 and sensing (illuminance, proximity, colour, and spectrum detection) for indoor envirIn this project a novel portable Visible Light Communication (VLC) system comprising an inexpensive and easy to fabricate multi-channel transmitter (Tx) and a receiver (Rx) have been developed. The light engine is designed to support up to three different LED channels while illuminating an indoor space changing the spectrum according to human circadian rhythms or any other desires. The Tx module architecture contains a programmable microcontroller and a constant current LED driver to manage the data to be transmitted. The Rx module allows the detection of optical signals, decoding and recovering the complete information with a circuit containing three stages: transimpedance amplifier, serializer and deserializer stages, controlled by a microcontroller unit. The VLC link has been tested in a laboratory environment with natural illumination to operate for distances up to 8 meters (at 700 kbps), data rates up to 4.50 Mbps (at 2 meters), and angles up to 75º (at 700 kbps and 2 meters). Under these conditions the flickering effect is completely removed

Spatial and wavelength division multiplexing for high-speed VLC systems: An overview

White light emitting diodes (LEDs) are becoming the primary source of illumination for the home and office environment. These LEDs can be intensity modulated to transmit high-speed data via an optical carrier. As a result, there is a paradigm shift in indoor wireless communication as the illumination infrastructure can be reused for data communications. It is widely expected that visible light communication (VLC) system will play a significant role in realizing the high-speed data communication envisaged for 5G connectivity. The goal of VLC systems is to provide a reliable and ubiquitous communication link that is an order of magnitude faster than current radio frequency (RF) links. In order to support the high data rates required for the current and future generations of communication systems, a number of techniques were explored for VLC by a number of research groups worldwide. This paper provides an overview of spatial and wavelength division multiplexing that has enabled multi-Gb/s transmission speeds in VLC using low bandwidth LEDs

Spatial Interference Detection for Mobile Visible Light Communication

Taking advantage of the rolling shutter effect of CMOS cameras in smartphones is a common practice to increase the transfered data rate with visible light communication (VLC) without employing external equipment such as photodiodes. VLC can then be used as replacement of other marker based techniques for object identification for Augmented Reality and Ubiquitous computing applications. However, the rolling shutter effect only allows to transmit data over a single dimension, which considerably limits the available bandwidth. In this article we propose a new method exploiting spacial interference detection to enable parallel transmission and design a protocol that enables easy identification of interferences between two signals. By introducing a second dimension, we are not only able to significantly increase the available bandwidth, but also identify and isolate light sources in close proximity

Employing VLC technology for transmitting data in biological tissue

Abstract. With the development in wireless communication methods, visible light communication (VLC), a subset of Optical Wireless Communication (OWC) has garnered much attention to employ the technology for a secure short-range wireless communication. We present a feasibility study to determine the performance of VLC in short range wireless transmission of data through biological tissue. VLC is a cost efficient and secure means of transmitting high volume of data wirelessly which can considerably reduce the interference issues caused by electromagnetic pulses and external electric fields. We present a simple measurement approach based on Monte Carlo simulation of photon propagation in tissue to estimate the strength of wireless communication with body implant devices. Using light for communication brings inherent security against unauthorized access of digital data which could be acquired from the low energy body implant devices used for medical diagnosis and other studies. This thesis discusses the typical components required to establish VLC such as, transmitter, receiver and the channel mediums. Furthermore, two cases of Monte Carlo simulation of photon-tissue interaction are studied to determine a possibility if VLC is a suitable substitute to radio frequency (RF) for a more wireless communication with the body implants. The process of theoretical measurement begins with conversion of light intensity into an electrical signal and an estimation of achievable data rate through a complex heterogeneous biological tissue model. The theoretically achieved data rates of the communication were found to be in the order of megabits per second (Mbps), ensuring a possibility to utilize this technology for short range reliable wireless communication with a wider range and application of implant medical devices. Biophotonics.fi presents a computational simulation of light propagation in different types of computational tissue models comprehensively validated by comparison with the team’s practical implementation of the same setup. This simulation is also used in this thesis (5.2.2) to approximate more accurate data rates of communication in case of a practical implementation