Antennas for wide area distributed RFID systems

© 2020 IEEE. This paper describes the use of Wide Area Distributed RFID Systems to enable wide area coverage of UHF RFID with high likelihood of tags anywhere within the area being successfully detected. The implications on antenna design are discussed and novel loop antenna meeting the requirements is presented

Linearisation Method of DML-Based Transmitters for Optical Communications Part I: Theory and Simulation Studies

The performance of directly-modulated lasers (DMLs) is severely impaired by nonlinear behaviour when operating at high symbol rates. We propose a new linearization method for DML-based transmitters which can significantly reduce nonlinearity. This method, named the Stretched A (StrA) method, relies on the generation of an approximation to the ideal modulating current that generates a linear optical output waveform. In Part I of this work, the theoretical framework of the proposed method is presented and detailed simulation studies illustrate its implementation and demonstrate the benefits it offers. Although the method is applicable to any type of DML, the simulation studies presented herein focus on optical links based on vertical-cavity surface-emitting lasers (VCSELs) as these comprise the vast majority of short-reach optical links. Part II of this work presents the proof-of-principle experimental demonstration of this new linearization method and discusses its possible implementations using either analog or digital electronics

Submicron active-passive integration for InP-based membranes on silicon

The high vertical index contrast and the small thickness of thin InP-based membrane structures bonded with BCB on Silicon allow the realization of very small devices. To make photonic integrated circuits with both passive and active components in these membranes, active-passive integration on a small scale is essential. In this paper we will present our results on sub-micrometer active areas for membrane applications

Coexistence of high-bit-rate quantum key distribution and data on optical fiber

Quantum key distribution (QKD) uniquely allows distribution of cryptographic keys with security verified by quantum mechanical limits. Both protocol execution and subsequent applications require the assistance of classical data communication channels. While using separate fibers is one option, it is economically more viable if data and quantum signals are simultaneously transmitted through a single fiber. However, noise-photon contamination arising from the intense data signal has severely restricted both the QKD distances and secure key rates. Here, we exploit a novel temporal-filtering effect for noise-photon rejection. This allows high-bit-rate QKD over fibers up to 90 km in length and populated with error-free bidirectional Gb/s data communications. With high-bit rate and range sufficient for important information infrastructures, such as smart cities and 10 Gbit Ethernet, QKD is a significant step closer towards wide-scale deployment in fiber networks.Comment: 7 pages, 5 figure

A 3D Ray-tracing Model for UHF RFID

In this work, a 3-dimensional (3D) ray-tracing model is proposed. The model is specifically tailored for RFID applications by taking into account some of its unique characteristics. The proposed model can give accurate power predictions and is suitable for indoor RFID systems operating with low fade margins. The model has been verified by comparison with Method of Moments (MoM) and practical measurements. It is shown to achieve a high accuracy with significantly less computational complexity than MoM. An example application of the model is presented comparing the performance of two antennas with similar beam patterns but different axial ratio. The predicted tag detection rates (63% and 50%) are in good agreement with the experimental data (65% and 55%), showing the accuracy of the model and its improvement over previous models which are not able to handle axial ratio as accurately.This work was supported by EPSRC EP /S-19405/1 Channel Optimised Distributed Passive Sensor Networks

Random lasing action from PMMA waveguide doped with CdSe/ZnS CQDs plasmonically enhanced by Ag nanoislands

In this letter, the random laser is fabricated by an active waveguide structure constructed by covering the layer of poly methyl methacrylate (PMMA) doped CdSe/ZnS colloidal quantum dots (CQDs) onto the Ag nanoisland structures. There is a low threshold due to the excellent overlap of the plasmonic resonance of the Ag nanoislands with the photoluminescence spectrum of the CQDs and the strong confinement mechanism provided by the active waveguide layer. The performances of random laser can be tuned through the flexible fabrication of Ag nanoisland structures. The spectral evolution shows a stability of random lasing under uninterrupted laser irradiation owing to the super chemical and photo stability of CdSe/ZnS CQDs and the stable external environment for CdSe/ZnS CQDs provided by the PMMA matrix.National Natural Science Foundation of China Grant n. 11174160, Grant n. 11474052 and Grant n. 11274062. Jiangsu Overseas Visiting Scholar Program for University Prominent Young & Middle-Aged Teachers and Presidents under N. 2018001

High-efficient Converged Digital Radio over Fibre (DRoF) Transmission and Processing for Indoor Both Cellular and IoT Services

© 2019 IEEE. Digital Radio over fibre (DRoF) transmission has long been considered as a promising solution for providing multiple wireless services over a single optical-wireless infrastructure for indoor and last-mile wireless coverage. However, with the increasing number of services and fast growing requirement of Internet of things (IoT), the existing technologies are not able to meet the demand of network convergence due to high capital expenditure (CAPEX) and operating expenditure (OPEX) in managing the vast amount of digitised data. In this paper, we demonstrate a compact multiservice hybrid fibre radio scheme for both downlink and uplink where a novel digital signal processing method and a novel fronthaul protocol are implemented with high bandwidth efficiency. The system uses pluggable modular RF frontend and digital cards so as to support the increasing services dynamically. Both RFID based IoT services and several cellular services from mobile network operators (MNOs) are converged onto a single <6Gbps optical link with high spectral efficiency, modulation accuracy and RF performance. The system is experimentally demonstrated and shows low EVM for all cellular services provided from China Unicom and high detection rate and localisation accuracy for the RFID service carried over 20km optical fibre link