Wensheng Zhai

An orbital angular momentum radio communication system optimized by intensity controlled masks effectively: Theoretical design and experimental verification

A system of generating and receiving orbital angular momentum (OAM) radio beams, which are collectively formed by two circular array antennas (CAAs) and effectively optimized by two intensity controlled masks, is proposed and experimentally investigated. The scheme is effective in blocking of the unwanted OAM modes and enhancing the power of received radio signals, which results in the capacity gain of system and extended transmission distance of the OAM radio beams. The operation principle of the intensity controlled masks, which can be regarded as both collimator and filter, is feasible and simple to realize. Numerical simulations of intensity and phase distributions at each key cross-sectional plane of the radio beams demonstrate the collimated results. The experimental results match well with the theoretical analysis and the receive distance of the OAM radio beam at radio frequency (RF) 20 GHz is extended up to 200 times of the wavelength of the RF signals, the measured distance is 5 times of the original measured distance. The presented proof-of-concept experiment demonstrates the feasibility of the system.

Measurement of the rotational Doppler frequency shift of a spinning object using a radio frequency orbital angular momentum beam

An indirect approach based on phase measurement is proposed to measure the rotational Doppler frequency shift, which takes full advantage of the phase structure of orbital angular momentum (OAM) beams in radio domain, using a vector network analyzer (VNA) as a phase discriminator. A proof-of-concept experiment is established by an optical-controlled system with the OAM state of 1. By analyzing the experiments results, the rotational Doppler frequency shift is measured as 24.83 Hz (max error rate 0.67%) at 50π rad/s rotational velocity, deducing the rotational velocity as 50.18π (average error rate 0.36%).

Compensation of chromatic-dispersion for full-duplex radio-over-fiber links with vector signal transmission using frequency tripling

This paper demonstrates the theory of chromatic dispersion (CD)-induced constellation rotation (CR) in a radio-over-fiber (ROF) link, and a symmetry theory for compensation. A 60 GHz full-duplex ROF system with vector signal transmission using frequency-tripling modulation (FTM) is also proposed. The simulations for both 5 Gbps and 200 Mbps 16 QAM signal transmission show that the CD-induced CR can be entirely overcome due to the proposed method, and the proposed ROF schedule still maintains good performance even after 500 km of 200 Mbps vector signal transmission. Meanwhile, the central station is significantly simplified and cost-effective since only one 15 GHz local oscillator is needed for both the generation of an optical millimeter-wave signal and the carrier of the downlink intermediate-frequency (IF) signal.

Bidirectional radio over fiber system with wavelength reuse based on optical carrier polarization-suppressed DSB modulation

To overcome the limitation of wavelength-dependent optical filter, we have experimentally demonstrated a bidirectional RoF system based on carrier polarization-suppressed DSB modulation. After transmitted over 10.5-km SMF, 0.3-dB power penalty is achieved for bidirectional links.

Optical-controlled pencil-beam steering phased-array based on FD-OP

A pencil-beam steering phased-array based on optical-controlling scheme is proposed. FD-OP is used to gain flexibility and high tunablility. Experiments are conducted at 17 GHz to validate the 2D beams-steering ability of the system.

Mode measurement of a dual-mode radio frequency orbital angular momentum beam by circular phase gradient method

A measurement method of dual-mode radio frequency orbital angular momentum (RF-OAM) beams is proposed, dedicated to meeting the practical needs of the orbital angular momentum mode-division multiplexing (OAM-MDM) in free-space communication. Theoretical analysis and numerical simulations are conducted to demonstrate that a dual-mode OAM beam can be unambiguously measured by gathering the phase gradient function of a circle around the OAM beam axis and calculating its average value and PV (peak/valley) factor. A proof-of-concept experiment is presented, which employs a single receiving antenna on a rotatable plane to measure mode +1 and –2 of a dual-mode OAM beam.

Design for shared backup path protection based on content connectivity against disaster in elastic optical datacenter networks

Disaster, natural or man-made, is the main threaten of survivability and reliability of networks. The development of content connectivity provides a new way of protection against disaster to ensure the reliability of network service/content. This paper focuses on shared backup path protection based on content connectivity against disaster in the context of elastic optical datacenter networks. In this work, we propose an integrated Integer Linear Program (ILP) for an optical datacenter network design to minimize both the required spare capacity and the working resources. We also propose a heuristic algorithm for large datacenter networks.

Full-Duplex ROF Link with Seamless Convergence and High-Speed Broadband Wireless Access

Full-duplex ROF link with seamless convergence and high-speed broadband wireless access is proposed. The simulation of V-band (62.4GHz) and conventional 802.11n (2.4GHz) with 16QAM signal transmission shows that our novel schedule maintains quite good performance.