Beyond the 100 Gbaud directly modulated laser for short reach applications

It is very attractive to apply a directly modulated laser (DML)-based intensity-modulation and direct-detection (IM/DD) system in future data centers and 5G fronthaul networks due to the advantages of low cost, low system complexity, and high energy efficiency, which perfectly match the application scenarios of the data centers and 5G fronthaul networks, in which a large number of high-speed optical interconnections are needed. However, as the data traffic in the data centers and 5G fronthaul networks continues to grow exponentially, the future requirements for data rates beyond 100 Gbaud are challenging the existing DML-based IM/DD system, and the main bottleneck is the modulation bandwidth of the DML. In this paper, the data rate demands and technical standards of the data centers and 5G fronthaul networks are reviewed in detail. With the modulation bandwidth requirements, the technical routes and achievements of recent DMLs are reviewed and discussed. In this way, the prospects, challenges, and future development of DMLs in the applications of future data centers and 5G fronthaul networks are comprehensively explored

Optical generation/detection of broadband microwave orbital angular momentum modes

In this article, a novel electrically controlled optical broadband phase shifter (ECO-BPS) is proposed and experimentally investigated for broadband microwave orbital angular momentum (OAM) mode generation. Based on the proposed ECO-BPS and a 17-element circular antenna array, the effect of the phase error on the OAM mode quality is studied by comparing the OAM modes respectively synthesized by three phase schemes: ideal phase shifts, ECO-BPS phase shifts, and optical true time delay phase shifts. In addition, the crosstalk caused by the phase error in applications of OAM modes multiplexing is investigated in a Dammann vortex grating based OAM modes demultiplexing system. All numerical simulation results demonstrate the feasibility of the ECO-BPS in broadband microwave OAM applications

Optical generation/detection of broadband microwave orbital angular momentum modes

\u3cp\u3eIn this article, a novel electrically controlled optical broadband phase shifter (ECO-BPS) is proposed and experimentally investigated for broadband microwave orbital angular momentum (OAM) mode generation. Based on the proposed ECO-BPS and a 17-element circular antenna array, the effect of the phase error on the OAM mode quality is studied by comparing the OAM modes respectively synthesized by three phase schemes: ideal phase shifts, ECO-BPS phase shifts, and optical true time delay phase shifts. In addition, the crosstalk caused by the phase error in applications of OAM modes multiplexing is investigated in a Dammann vortex grating based OAM modes demultiplexing system. All numerical simulation results demonstrate the feasibility of the ECO-BPS in broadband microwave OAM applications.\u3c/p\u3

Experimental demonstration of 9.6 Gbit/s polar coded infrared light communication system

A new inter-frame polar coded modulation scheme is proposed and experimentally demonstrated in an infrared light communication (ILC) system. The scheme utilizes the Monte Carlo (MC) method to jointly design an inter-frame polar code with 16-ary quadrature-amplitude modulation (16QAM) and orthogonal frequency-division multiplexing (OFDM). The indoor transmission of 9.6 Gbit/s 16QAM OFDM signal is experimentally achieved over a 3.2 km single-mode fiber and 0.8 m free space. The experiment results show that the proposed scheme employing a polar code of length 1024 and cyclic redundancy check aided successive cancellation list (CA-SCL) decoding with a list size of 2 resulted in no errors over 107 bits. Moreover, the proposed scheme requires negligible extra decoding complexity with respect to its classical counterpart, MC-constructed polar coded modulation. To the best of our knowledge, this is the first experimental demonstration of a polar coded modulation based infrared light communication system

A 20‐Gbps Beam‐Steered Infrared Wireless Link Enabled by a Passively Field‐Programmable Metasurface

Beam steering is one of the main challenges in energy‐efficient and high‐speed infrared light communication. To date, active beam‐steering schemes based on a spatial light modulator (SLM) or micro‐electrical mechanical system (MEMS) mirror, as well as the passive ones based on diffractive gratings, are demonstrated for infrared light communication. Here, for the first time to the authors' knowledge, an infrared beam is steered by 35° on one side empowered by a passively field‐programmable metasurface. By combining the centralized control of wavelength and polarization, a remote passive metasurface can steer the infrared beam in a remote access point. The proposed system has the scalability to support multiple beams, flexibility to steer the beam, high optical efficiency, simple and cheap devices on remote sides, and centralized control (low maintenance cost), while it avoids disadvantages such as grating loss, a small coverage area, and a bulky size. Based on the proposed beam‐steering technology, a proof‐of‐concept experiment system with a data rate of 20 Gbps is also demonstrated