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As the mobile communication evolves from sub-6 GHz to millimeter wave (MMW) frequency bands, the demand for high-speed wireless transmission rates exceeding hundreds of gigabits per second is becoming more and more prominent. It is one of the important cornerstones supporting numerous emerging bandwidth-consuming applications represented by the metaverse, digital twin and so on. So far, there is a huge room for improvement in wireless transmission rate, which is far inferior to the transmission capacity of fiber optic links. In this paper, we have proposed and experimentally demonstrated a large-capacity photonics-assisted MMW wireless communication system over 20-km fiber and 1.3-m wireless transmission at the W band. A dual-polarized single-input single-output (SISO) wireless link, instead of the commonly used 2 × 2 multiple-input multiple-output (MIMO) links, is used for the transparent transmission of optical polarization division multiplexing signal, which significantly simplifies the system complexity and enhances its robustness. In addition, the transmission performance is further improved by employing an advanced MIMO Volterra nonlinear equalizer. With the bit error ratio threshold of 2 × 10−2, a record single-lane single-carrier wireless air interface rate (WAIR/ch/λ) up to 504 Gb/s has been achieved for the first time. This solution we proposed provides opportunity for progress in the wireless air interface capacity close to the fiber-optic transmission capacity in the fiber-wireless integration transmission systems.

An ultrasmall polarization splitter and rotator (PSR) on a silicon-on-insulator (SOI) platform is proposed based on an asymmetric directional coupler (ADC) consisting of a bridged subwavelength grating (BSWG) and a strip silicon waveguide with another SWG embedded in the middle slot. The inputting TE mode is tightly confined in BSWG and directly passes through a bar port with little coupling to the adjacent waveguide because of the phase mismatch, while the phase-matching condition allows the injected TM mode to be evanescently decoupled from BSWG and simultaneously converted into the TE mode supported by a SWG slot waveguide before propagating out through the cross port. Both polarization-dependent behaviors within the proposed PSR can be readily realized and efficiently manipulated by independently controlling the attributes of the ADC waveguides, which are distinctly engineered by different SWG segments. We have verified what we believe, to the best of our knowledge, is the first combination of BSWG and a SWG slot waveguide that provides an additional degree of freedom in the design and a stronger modal hybridization due to the doubled effects from jointly used SWGs. Further, the increasing number of inserted SWGs in the present device drastically reduces the device footprint, leading to a coupling length of only 5.5 µm. From the results, the conversion loss of −0.28dB (polarization conversion ratio of 93.7%) has been obtained for a TM-to-TE conversion at 1.55 µm. The TM mode of the resulting PSR shows its cross talk is less than −14.3dB and the conversion loss is better than −0.63dB in a 95 nm bandwidth that has covered the entire C and L bands. The cross talk and insertion loss of the TE mode are lower than −29dB and −0.42dB, respectively, as the operating wavelength varies.