Ultra-Low Cost High-Density Two-Dimensional Visible-Light Optical Interconnects

© 2019 IEEE. Visible light communications have attracted considerable interest in recent years owing to the ability of low-cost light emitting diodes (LEDs) to act both as illumination sources and data transmitters with moderate data transmission rates. In this paper, we propose the formation of ultra-low cost visible-light integrated optical links by interfacing dense micro-pixelated LED arrays with matching multi-layered multimode polymer waveguide arrays. The combination of these two optical technologies can offer relatively high aggregate data densities ≥ 0.5 Tb/s/mm2 using very low cost components that can be directly interfaced with CMOS electronics and integrated onto standard printed circuit boards. Here, we present the basic system design and report the first proof-of-principle demonstration of such a visible light system employing 4×4 μLED arrays on a pitch matching four-layered waveguide array samples. Different interconnection topologies and light coupling schemes are investigated and their performance in terms of loss and crosstalk is compared. Data transmission of 2.5 Gb/s with a bit error rate within the forward-error correction threshold of 3.8×10-3 is achieved over a single μLED-waveguide channel using PAM-4 modulation and equalization. The results presented here demonstrate the potential of such ultra-low cost visible-light optical interconnects.UK EPSRC via the Ultra Parallel Visible Light Communications Project (EP/K00042X/1

2 Gb/s μlED-APD based visible light communications using feed-forward pre-equalization and PAM-4 modulation

Feed-forward pre-equalization is investigated to extend the transmission capability of μLED-based links, providing better receiver sensitivities up to 5dB compared with post-equalization. Error-free 2Gb/s free-space VLC over 0.6m is demonstrated using a PAM-4 modulated blue μLED and an APD receiver.This work is supported by the UK EPSRC via the UPVLC Project.This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/ECOC.2015.734188

μlED-Based Single-Wavelength Bi-directional POF Link with 10 Gb/s Aggregate Data Rate

We report record 10 Gb/s bi-directional data transmission over a single 10 m SI-POF, by employing blue micro-light-emitting diodes (μLEDs) at a single wavelength, APD receivers and a PAM-32 modulation scheme. The implementation of 10 Gb/s LED-POF links takes advantage of the bi-directional configuration, which doubles the overall channel capacity, and APDs which provide an enhanced link power budget owing to their improved sensitivity compared with conventional PIN photodiodes. Moreover, the high spectral efficiency of the PAM-32 modulation scheme employed, together with equalization techniques, enable the full utilization of the link bandwidth and the transmission of data rates higher than those obtained with conventional on-off-keying (OOK). Simulation and experimental results demonstrate the feasibility of such a bi-directional link and simultaneous 5 Gb/s data transmission is realized in each direction, achieving an aggregate data rate of 10 Gb/s with a BER<10-3. The crosstalk penalty between the two directions of the link is measured to be less than 0.5 dB.This is the final version of the article. It first appeared from IEEE via http://dx.doi.org/10.1109/JLT.2015.244398

6.25 Gb/s POF link using GaN μLED arrays and optically generated pulse amplitude modulation

Optically-generated PAM schemes using μLED arrays are implemented for high-speed POF links for the first time. 6.25Gb/s PAM-16 transmission is demonstrated using 4 μLEDs, exhibiting 3.8dB greater power-margin than a link with a single μLED.This work is supported by the UK Engineering and Physical Sciences Research Council (EPSRC) via the Ultra Parallel Visible Light Communication (UP-VLC) Project.This is the accepted manuscript of a paper published in CLEO: 2015 (X. Li, N. Bamiedakis, J. Wei, J. Mckendry, E. Xie, R. Ferreira, E. Gu, M. Dawson, R. V. Penty, and I. H. White, "6.25 Gb/s POF Link Using GaN μLED Arrays and Optically Generated Pulse Amplitude Modulation," in CLEO: 2015, OSA Technical Digest (online) (Optical Society of America, 2015), paper STu4F.7.). The final version is available at http://dx.doi.org/10.1364/CLEO_SI.2015.STu4F.7 © 2015 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited

High Bandwidth GaN-Based Micro-LEDs for Multi-Gb/s Visible Light Communications

Gallium-nitride (GaN) based light-emitting diodes (LEDs) are highly-efficient sources for general purpose illumination. Furthermore, being semiconductor-based light sources, they are readily compatible with intelligent drive electronics. Visible light communications (VLC) is a technology which leverages these advantageous properties of GaN LEDs and can supplement existing wireless communications by offering a large, licence-free spectral bandwidth. Here we report on progress in the development of micro-scale GaN LEDs (micro-LEDs), optimised for VLC. These blue-emitting micro-LEDs are shown to have very high electrical-to-optical modulation bandwidths, exceeding 800~MHz. The data transmission capabilities of the micro-LEDs are illustrated by demonstrations using on-off-keying (OOK), pulse-amplitude modulation (PAM) and orthogonal frequency division multiplexing (OFDM) modulation schemes to transmit data over free space at rates of 1.7, 3.4 and 5 Gb/s, respectively

High-Aggregate-capacity visible light communication links using stacked multimode polymer waveguides and micro-pixelated LED arrays

In recent years Light emitting diodes (LEDs) have gained renewed interest for use in visible light communication links (VLC) owing to their potential use as both high-quality power-efficient illumination sources as well as low-cost optical transmitters in free-space and guided-wave links. Applications that can benefit from their use include optical wireless systems (LiFi and Internet of Things), in-home and automotive networks, optical USBs and short-reach low-cost optical interconnects. However, VLC links suffer from the limited LED bandwidth (typically ∼100 MHz). As a result, a combination of novel LED devices, advanced modulation formats and multiplexing methods are employed to overcome this limitation and achieve high-speed (>1 Gb/s) data transmission over such links. In this work, we present recent advances in the formation of high-Aggregate-capacity low cost guided wave VLC links using stacked polymer multimode waveguides and matching micro-pixelated LED (μLED) arrays. μLEDs have been shown to exhibit larger bandwidths (>200 MHz) than conventional broad-Area LEDs and can be formed in large array configurations, while multimode polymer waveguides enable the formation of low-cost optical links onto standard PCBs. Here, three-And four-layered stacks of multimode waveguides, as well as matching GaN μLED arrays, are fabricated in order to generate high-density yet low-cost optical interconnects. Different waveguide topologies are implemented and are investigated in terms of loss and crosstalk performance. The initial results presented herein demonstrate good intrinsic crosstalk performance and indicate the potential to achieve ≥ 0.5 Tb/s/mm2 aggregate interconnection capacity using this low-cost technology

Ultra-Low Cost High-Density Two-Dimensional Visible-Light Optical Interconnects

© 2019 IEEE. Visible light communications have attracted considerable interest in recent years owing to the ability of low-cost light emitting diodes (LEDs) to act both as illumination sources and data transmitters with moderate data transmission rates. In this paper, we propose the formation of ultra-low cost visible-light integrated optical links by interfacing dense micro-pixelated LED arrays with matching multi-layered multimode polymer waveguide arrays. The combination of these two optical technologies can offer relatively high aggregate data densities ≥ 0.5 Tb/s/mm2 using very low cost components that can be directly interfaced with CMOS electronics and integrated onto standard printed circuit boards. Here, we present the basic system design and report the first proof-of-principle demonstration of such a visible light system employing 4×4 μLED arrays on a pitch matching four-layered waveguide array samples. Different interconnection topologies and light coupling schemes are investigated and their performance in terms of loss and crosstalk is compared. Data transmission of 2.5 Gb/s with a bit error rate within the forward-error correction threshold of 3.8×10-3 is achieved over a single μLED-waveguide channel using PAM-4 modulation and equalization. The results presented here demonstrate the potential of such ultra-low cost visible-light optical interconnects

Optimum device and modulation scheme selection for optical wireless communications

There has been extensive modelling of the optical wireless channel, and the optimum modulation scheme for a particular channel is well-understood. However, this modelling has not taken into account the trade-offs that transmitter and receiver selection usually involve. For a particular type of transmitter, the modulation bandwidth and available power are closely related, as are receiver bandwidth, active area and sensitivity. In this paper, we present a design approach that takes this device selection into account. The paper details a general design method for an optical wireless communication system using a holistic design approach (i.e. considering channel, modulation schemes and device constraints). The paper shows results for particular examples, showing a substantial increase in margin (or data-rate) is available using this approach. For instance, by using this approach mutually optimising both modulation schemes and device constraints, it is found that for an optimally chosen Gallium Nitride micro-LED and a commercial photo receiver pair, a 20 dB SNR margin (or ~3 times data-rate improvement) can be obtained compared with a more typical approach mainly concerning the modulation scheme optimisation

11 Gb/s WDM transmission over SI-POF using violet, blue and green μlEDs

Proof-of-principle coarse WDM transmission over SI-POF is demonstrated employing μLEDs, an APD receiver and PAM modulation. A record aggregate data rate of 11 Gb/s is achieved over 10 m of POF with a BER<10-3