A record 4.343 Gbit/s green color micro-light-emitting-diode (μ-LED) based visible-light-communication (VLC) is demonstrated. We designed and fabricated the InGaN/GaN μ-LED array with modulation bandwidth >1.1 GHz. The micro-LED was grown on semipolar (20-21) orientation, which could offer higher modulation bandwidth at a lower current density.

we put forward and demonstrate a steerable optical beam visible light communication (VLC) system combining orthogonal frequency division multiplexing (OFDM) and non-orthogonal multiple access (NOMA) schemes, and utilizing a spatial light modulator (SLM)-based reconfigurable intelligent surface (RIS) for beam steering. When utilizing the SLM as RIS for optical beam steering, its operation principle, maximum achievable steering angle (i.e. field-of-view, FOV), as well as the corresponding loss should be analyzed. We theoretically and experimentally analyzed in detail the characters of SLM when acting as the RIS. Experimental results demonstrate the flexibility of both active beam control and data rate allocation for multiple users. The SLM-based RIS can independently and simultaneously control multiple beams, and significantly reduce the deploying cost of the increase in the devices for the multi-beam handling scenario. All of the specified channels under evaluation satisfy the pre-forward error correction bit-error rate limit (pre-FEC BER = 3.8 × 10 ^-3 ).

With the evolution of underwater wireless optical communications, semiconductor lasers, particularly blue and green diode lasers, have exhibited high performance as optical transmission sources. They have a wide modulation bandwidth and can offer data rates in the Gb/s range in pure water. However, blue and green wavelengths experience higher attenuation coefficients and more considerable scattering losses in the turbid harbor and turbulent water compared to red light. In this study, we investigated the capability of red vertical-cavity surface-emitting lasers (VCSELs) for data transmission in an underwater wireless optical communication (UWOC) system. The wavelength of our VCSEL is ~645 nm, and the output power is ~2 mW. A 2-Gb/s data rate was achieved underwater by direct-current-biased orthogonal frequency-division multiplexing (DC-OFDM) modulation. The bit error ratio (BER) was $3.5\times 10 ^{\mathbf {-3}}$ , which is below the hard-decision forward error correction (HD-FEC) limit of $3.8\times 10 ^{\mathbf {-3}}$ . The availability of 650-nm transmission window of plastic optical fibers (POFs) makes this VCSEL wavelength an attractive solution for POF communication and UWOC convergent systems. Moreover, the use of this wavelength will enable wavelength division multiplexing (WDM) in highly turbid water with other red wavelengths (e.g., 680 nm) to improve the data throughput in these harsh environments.

In order to achieve high-capacity visible light communication (VLC), five dimensions in physics, including frequency, time, quadrature modulation, space, and polarization can be utilized. Orthogonality should be maintained in order to reduce the crosstalk among different dimensions. In this work, we illustrate a high-capacity 21.01 Gbit/s optical beam steerable VLC system with vibration mitigation based on orthogonal frequency division multiplexed (OFDM) non-orthogonal multiple access (NOMA) signals using red, green, and blue (RGB) laser-diodes (LDs). The OFDM-NOMA can increase the spectral efficiency of VLC signal by allowing high overlapping of different data channel spectra in the power domain to maximize the bandwidth utilization. In the NOMA scheme, different data channels are digitally multiplexed using different levels of power with superposition coding at the transmitter (Tx). Successive interference cancellation (SIC) is then utilized at the receiver (Rx) to retrieve different power multiplexed data channels. The total data rates (i.e., Data 1 and Data 2) achieved by the R/G/B OFDM-NOMA channels are 8.07, 6.62, and 6.32 Gbit/s, respectively, achieving an aggregated data rate of 21.01 Gbit/s. The corresponding average signal-to-noise ratios (SNRs) of Data 1 in the R, G, and B channels are 9.05, 9.18 and 8.94 dB, respectively, while that of Data 2 in the R, G, and B channels are 14.92, 14.29, and 13.80 dB, respectively.

Optical sensing and communication systems are essential for various applications in terrestrial, space, and submarine environments. However, integrating these systems poses several challenges, especially in terms of energy sustainability and management. In this work, we report on energy harvesting over fiber (EHoF) using amplified spontaneous emission (ASE) from erbium-doped fiber amplifiers (EDFAs). We demonstrate that the transmitted ASE power that is wasted in fiber Bragg grating (FBG) sensors and the ASE noise that is filtered out in optical communication systems can be harnessed for EHoF. We present a multi-functional system that includes EHoF, FBG-based sensing, fiber-optic communication, and underwater optical wireless communication (UOWC), and discuss the performance metrics of the different modules. This multi-functional system successfully harvests 6.12 mW of electrical power while enabling up to 2.5 Gbps of hybrid optical fiber and UOWC data communication with simultaneous temperature sensing using FBG in an underwater environment.

In order to increase transmission capacity, multiplexing schemes in different physical dimensions, including time, frequency, modulation quadrature, polarization, and space, can be employed. In this work, we propose and demonstrate a red color laser-diode (LD) based visible-light-communication (VLC) system using two kinds of digital domain multiplexing schemes, orthogonal-frequency-division-multiplexing (OFDM) and power-domain division-multiplexing (PowDM). The two digital domain multiplexed data can achieve data rates of 1.66 Gbit/s and 6.41 Gbit/s, respectively, providing a total data rate of 8.07 Gbit/s, fulfilling the pre-forward error correction (pre-FEC) bit-error-rate (BER) limit. The measured signal-to-noise ratios (SNRs) are 10.96 dB and 14.45 dB, respectively. Here, similar to OFDM, the PowDM can enhance the total system capacity by allowing acceptable signal spectra overlapping among different power division signals to maximize the bandwidth utilization. An experiment to verify and evaluate the proposed work is performed. The modulation and demodulation of OFDM and PowDM are discussed. The optimum power levels of the individual signals in the PowDM signal are also analyzed.