μLED-Based Single-Wavelength Bi-directional POF Link With 10 Gb/s Aggregate Data Rate

Abstract

We report record 10 Gb/s bi-directional data transmission over a single 10 m SI-POF, by employing blue microlightemitting 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 p-i-n 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. 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.

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

“…For example by reducing the LED active area, and thereby decreasing capacitance and increasing current density, we have previously reported modulation bandwidths in excess of 400 MHz [5]. Such LEDs, with dimensions of 100x100 µm 2 or less, have been used to demonstrate 3 Gbps transmission over free-space [6] and 5 Gbps along a polymer optical fibre (POF) [7]. In this work, we report further advancement of these micro-LED sources.…”

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

“…As a result, an improved crosstalk performance is expected from this topology over the linear one. Based on earlier work on µLED-based optical links [12,43], we choose an array pitch p of 62.5 µm, a waveguide width of 30 µm and a µLED size of 20 µm for the work presented here, and we target received power levels of approximately -15 dBm and crosstalk values below -15 dB at each waveguide output. Such levels of received optical power and crosstalk should allow the transmission of data rates > 1 Gb/s over a single waveguide channel.…”

“…The most important simulation parameters are shown in Table II. The µLED response is modelled with an exponential, the APD response with a raised cosine with a roll-off factor of 0.2 [13,31] and the waveguide response with a Gaussian. The values used for the µLED output power and bandwidth and APD responsivity, bandwidth and noise performance are based on measured values of the actual devices, while the µLED driving condition matches the one used in the data transmission tests.…”

“…VLC systems based on light emitting diodes (LEDs) have attracted particular interest as low-cost LEDs can be used not only as high-quality and high-efficiency illumination sources but also as reliable optical sources for data transmission. Significant research has been carried out in recent years on the development, implementation and demonstration of LEDbased high-speed optical links for free-space communications (LiFi, Internet of Things, car-to-car communications) [4][5][6][7][8][9] and plastic optical fibre (POF) links for in-home and in-car networks [10][11][12]. Despite the limited LED bandwidth (typically a few tens of MHz), data rates beyond 1 Gb/s have been demonstrated over such links using a combination of techniques including advanced modulation formats, equalization and various multiplexing techniques [13][14][15][16].…”

“…The use of such µLED arrays can offer important advantages over vertical-cavity surface-emitting laser (VCSEL) arrays in shortreach optical links when relatively low data rates are required (~ few Gb/s): larger range of available wavelengths, eye-safe emission, reduced sensitivity to modal noise and temperature effects, and easier interface with electronic driving circuitry (direct CMOS interface). High-speed free-space and POFbased optical links have been demonstrated achieving data rates ≥ 5 Gb/s using a single µLED [8,28,31], while schemes employing multiple transmitters, such as optically-generated pulse amplitude modulation (PAM) schemes [32], multiple input multiple output (MIMO) systems [6] and coarse wavelength multiplexing have also been demonstrated using µLED arrays [15,33]. In addition, siloxane-based materials have been shown to exhibit high temperature resistivity in excess of 300°C and long lifetimes, while large multimode polymer waveguide arrays exhibiting low loss and low crosstalk have been cost-effectively integrated onto PCBs [34,35] and flexible substrates [36,37].…”