We experimentally demonstrate the photonics-aided wireless transmission of 4×4 multiple-input multiple-output (MIMO) probabilistic shaping 64-ary quadrature-amplitude-modulation (PS 64QAM) millimeter-wave signals at D-band (110-170GHz) over 3.1-m distance with a total bit rate of 1.056Tb/s and a bit-error ratio (BER) under 4×10-2. The employment of advanced digital-signal-processing (DSP) techniques, including probabilistic shaping, Nyquist shaping, and look-up-table (LUT) predistortion, significantly improves the transmission capacity and distance as well as the system performance. To the best of our knowledge, this is the first time to realize $\gt1-Tb/s$ millimeter-wave signal wireless delivery.

Vortex beams (VBs), characterized by helical phase front and orbital angular momentum (OAM), have shown perspective potential in improving communication capacity density for providing an additional multiplexing dimension. Here, we propose a diffractive deep neural network (D ² NN) method for OAM mode multiplexing and demultiplexing. By designing the D ² NN model and simulating light propagation through multiple diffractive screens, the phase and amplitude values can be automatically adjusted to manipulate the wavefront of light beams. Training the D ² NN model with mode coupler and separator functions, we convert VBs into target light fields with the diffraction efficiency exceeds 97%, and the mode purities are over 97%. Constructing an OAM multiplexing link, we successfully multiplex and demultiplex two OAM channels that carry 16-QAM signals in simulation, and the demodulated bit-error-rates are below 1×10 ^-4 . It is anticipated that the D ² NN can perform flexible modulation of multiple OAM modes, which may open a new avenue for high-capacity OAM communication and all-optical information processing, etc.

We experimentally demonstrate the downstream transmission of a 100 Gb/s/λ time division multiplexed passive optical network (TDM-PON) based on four-level pulsed amplitude modulation (PAM-4) in the O-band using 10 Gbps transmitters with semiconductor optical amplifier (SOA) and digital signal processing (DSP) at the receiver. Considering the soft-decision FEC (SD-FEC) threshold (1×10 $^{-2}$ ), power budget of 30.3 dB and 29.3 dB have been achieved after 22 km and 50 km fiber transmission, respectively. There is no observable dispersion penalty after 22 km and 50 km transmission. The possibility of 100 Gb/s/λ PON is first investigated using intensity modulation and direct detection (IM/DD) schemes rather than coherent detection schemes.

A modified look-up-table (LUT) nonlinear pre-distortion method is proposed. With the modified LUT method, the number of patterns and the computational complexity can be reduced by half with a similar system performance comparing with normal LUT. We experimentally demonstrate an 8-ary pulse amplitude modulation (PAM-8) intensity modulation and direct detection (IM/DD) transmission over 15-km fiber using directly modulated laser (DML) based on modified LUT. Around 1-dB receiver sensitivity improvement at BER of 3.8$\times$10-3 is achieved by adopting modified LUT over 15-km fiber transmission at 2Gbaud based on a commercial DML. In addition, we also experimentally demonstrate Mach-Zehnder modulator (MZM)-based 40Gbaud PAM-8 IM/DD transmission under BTB case, about 1-dB receiver sensitivity can also be improved.

Metasurfaces, kinds of planar ultrathin metamaterials, are able to modify the polarization, phase, and amplitude of physical fields of optical light by designed periodic subwavelength structures, attracting great interest in recent years. Based on the different type of the material, optical metasurfaces can be separated in two categories by the materials: one is metal and the other is dielectric. Metal metasurfaces rely on the surface plasma oscillations of subwavelength metal particles. Nevertheless, the loss caused by the metal structures has been a trouble, especially for devices working in transmit modes. The dielectric metasurfaces are based on the Faraday-Tyndall scattering of high-index dielectric light scattering particles. By reasonably designing the relevant parameters of the unit structure such as the size, direction, and shape, different functions of metasurfaces can realize and bring a wide range of applications. This article focuses on the metasurface concepts such as anomalous reflections and refractions and the working principle of different types of metasurfaces. Here, we briefly review the progress in developing optical over past few years and look into the near future.