Vision scheme based on the unmanned aerial vehicle (UAV) has gained widespread attention in recent years. Nevertheless, on account of the limited field-of-view of traditional images, it is difficult to apply to the fields that require comprehensive visual information. Therefore, a novel visual scheme based on the UAV platform with panoramic images is proposed in this paper, in which a platform consists of the panoramic cameras and the unmanned aerial vehicle are innovatively established and a scene recognition method based on discrete spherical image features are implemented. For the sake of reducing the distortion of panoramic image, we propose an icosahedron-based panoramic image representation for feature extraction, and then combined with the convolutional neural network and support vector machine, recognition task of the real image captured by the UAV platform are accomplished. Compared with the most widely used representation, namely the equirectangular projection, the proposed method can improve the recognition accuracy by 13.64% based on the Panoramic Scene dataset. Besides, our method can obtain a better performance even under the condition of large noise. Therefore, the proposed UAV-based panoramic scene recognition method can be applied to the fields that require comprehensive visual information effectively.
Optical networks-on-chip (ONoCs) using optical media to interconnect cores, have the advantages of high bandwidth, low power consumption and low latency. At present, mesh, torus and fat-tree are the most widely used topologies in ONoCs. Torus structure has the advantages of higher connectivity due to its annular structure. However, the traditional torus structure still has the problem of high end-to-end (ETE) delay. This paper proposes a new double-path ONoCs based on torus topology, named DPtorus. The DPtorus consists of two layers: one layer is a torus network divided into unit clusters, the other layer is an all-pass optical router. The dual-layer network is connected with each other by optical vias, so that there are two communication pathes between the source node and the target node in the network can be selected. The One is inter-cluster communication and the other is non-cluster communication. According to the comparison of the number of hop of the two communication paths, the communication path with fewer hops between the nodes is preferably selected to reduce the communication cost of the data packet. The network simulation results show that the DPtorus reduces latency and improves throughput compared to the torus network, resulting in better performance and enhanced reliability of network communications for the DPtorus.
We investigate the physical-layer security performance for a wireless-powered relaying mixed free-space optical-radio frequency (FSO-RF) system. In this system, a source transmits optical information to a relay (R), which decodes the received signal with a decode-and-forward protocol, converts it into an RF signal, and forwards it to a destination in the presence of an eavesdropper. Furthermore, we also assume that R has no extra power supply, and it only relies on harvesting energy from a power beacon to forward the information. Assuming that the FSO and all of the RF channels experience gamma-gamma and Rayleigh fading, the closed-form analytical expressions for secrecy outage probability and the probability of strictly positive secrecy capacity are derived. In addition, the effects of atmospheric turbulence, pointing errors, and detection techniques on the system performance are analyzed. Finally, we perform Monte Carlo simulations to verify the accuracy of the derived expressions.
The traditional optical networks-on-chip (ONoCs) communication systems is susceptible to crosstalk noise, especially the Wavelength Division Multiplexing (WDM) based ONoCs with nonlinear noise caused by four-wave mixing (FWM) effects. Crosstalk noise greatly reduces the performance and improves the bit error rate (BER) of the ONoCs. In this paper, a low BER communication system in ONoCs based on linear block codes is proposed. Firstly, we designed a all-optical linear block codes generator based on microring resonators(MRRs) to encode the information transmitted in the ONoCs before transmission. Secondly, a retransmission module is established that can resend the code groups that cannot be corrected. Combined with the error detection and error correction features of the linear block code, the BER of the communication in ONoCs can be effectively reduced. Finally, we verify the effectiveness of the proposed method through simulation. The simulation results show that compared with the traditional WDM-based ONoCs, applying the proposed system to ONoCs can greatly reduce the communication BER and effectively improve the communication performance of ONoCs.
Digital image facilitates further cultural exchanges while its potential safety hazards is becoming gradually aus- tere. Therefore assembling the characteristic superiorities of optical chaos and embedded hardware, experimental implementation of image encryption is of great academic value and application prospect. In this paper, we ex- perimental implement a color image encryption system based on optical chaos with ARM-embedded hardware. A vertical-cavity surface emitting laser (VCSEL) subject to positive optoelectronic feedback is utilized in the experiment, and the chaotic signal is gained under suitable parameters. The chaotic optical signal is trans- formed into optical chaotic data through an analog-to-digital converter. In our experiment, optical chaotic data dominates the image encryption process where the improved gravity model and the double sine map are served to encrypt the color image. The encrypted image can be conveyed securely through cloud services, and then our hardware board can inerrably decipher the encrypted image. Experimental results visibly illustrate that we successfully realized the encryption of color images.
Compared with optical network-on-chip (ONoC) with single wavelength, ONoC adopting wavelength division multiplexing (WDM) technology possesses a very prominent advantage—higher bandwidth. Therefore, WDM-based ONoC has been considered one of the most promising ways to relieve the rapidly increasing traffic load in communication systems. A WDM-based router, as the core equipment of WDM-based ONoC, is influenced by crosstalk noise, especially the nonlinear crosstalk noise generated by the four-wave mixing effect. Thus, to explore the performance of the N-port nonblocking optical router using WDM, we propose a universal analytic model to analyze the transmission loss, crosstalk noise, optical signal-to-noise ratio (OSNR), and bit error ratio (BER). The research results show that crosstalk noise varies along with signals at different wavelengths in the same channel. For signals with the same wavelength, the noises generated in the different transmission paths are obviously different from each other. For research of transmission loss, OSNR, and BER, similar results can be obtained. Based on the eye diagrams, we can learn that crosstalk noise will cause signal distortion to a certain extent. With this model, capability of this kind of multiport optical router using WDM can be understood conveniently.
The optical network-on-chip (ONoC) using WDM is the most promising candidate in MPSoCs for their strengths of high communication bandwidth, high energy efficiency, high transmission speed, lower latency and power dissipation. However, when WDM is utilized, new crosstalk noises are introduced, especially the four-wave mixing (FWM) crosstalk noise. In this paper, we propose a general crosstalk noise analysis model for the N-port nonblocking optical router in ONoC using WDM. As a case study, the transmission loss, crosstalk noise, and optical signal-to-noise ratio (OSNR) of the five-, six-port routers with eight wavelengths are presented. The results show the average OSNR is different for the different wavelength signals transmitted in the both routers. For the same channel, the OSNR is different among the signals with different wavelengths. For the same wavelength signal, the OSNR of different channels is also distinct.
A novel and compact metal-insulator-metal (MIM) waveguide coupled with dual hexagonal ring resonators is proposed and theoretically investigated using the temporal coupled-mode theory and finite-difference time-domain (FDTD) method. The numerical simulation results indicate that when the resonance wavelengths of the two hexagonal ring resonators differ from each other, the plasmon-induced transparency (PIT) phenomenon can be obtained. Furthermore, this plasmonic device is also demonstrated can be used as a logic device which implements the function of fundamental logical operations XOR and XNOR. This device is of significance to optical computing and optical networks-on-chip, and it may help to open up a new field for the application of surface plasmon polaritons (SPPs).
KEYWORDS: Signal attenuation, Signal to noise ratio, Waveguides, Optical components, Interference (communication), Switching, Optical engineering, Signal processing, Lanthanum, Network on a chip
Crosstalk noise and transmission loss are two key elements in determining the performance of optical routers. We propose a universal method for crosstalk noise and transmission loss analysis for the N-port nonblocking optical router used in photonic networks-on-chip. Utilizing this method, we study the crosstalk noise and transmission loss for the five-, six-, seven-, and eight-port optical routers. We ascertain that the crosstalk noise and transmission loss are different for different input–output pairs. For the five-port optical router, the maximum crosstalk noise ranges from 0 to −7.07 dBm, and the transmission loss ranges from −9.05 to −0.51 dB. Furthermore, based on the crosstalk noise and transmission loss, we analyze optical signal-to-noise ratio (OSNR) and bit error ratio (BER) for the five-, six-, seven-, and eight-port nonblocking optical routers. As the number of ports increases, the minimum average OSNR decreases and the average BER increases. In addition, in order to present the performance of the routers more visually, a fiber-optic communications system is designed to simulate the transmission processes of the signals of the different paths of the routers in Optisystem. The results show that the power amplitude of the input signal is obviously higher than the corresponding output signal. With this method, we can easily evaluate the transmission loss, crosstalk noise, OSNR, and BER of high-radix nonblocking optical routers and conveniently study the performance of the N-port optical router.
A plasmonic sensor based on a metal–insulator–metal waveguide with a side-coupled nanodisk resonator is proposed and numerically investigated using a finite-difference time-domain method. The numerical simulation results indicate that more than one sharp resonance dip appears in the transmission spectrum in the telecommunication regime, and each resonance wavelength has a linear relationship with the refractive index of the dielectric in the resonator. In addition, the sensing characteristics of the structure and the influence of its structural parameters are analyzed in detail by investigating the transmission spectra. As a refractive-index sensor, its sensitivity can reach as high as 1150 nm per refractive index unit near the resonance wavelength of 1550 nm, and its sensing resolution can reach 10−6 for a wavelength resolution of 0.01 nm. Furthermore, by employing the relationship between the temperature and the refractive index, the temperature-sensing characteristics of the structure are also discussed. Near the resonance wavelength of 1550 nm, the temperature sensitivity can reach 0.45 nm/°C. The sensor has a compact and simple structure and may find many potential and important applications in optical networks-on-chip and on-chip nanosensors.
A bidirectional chaos communication system, composed of 1550nm semiconductor lasers (SLs) and fiber links, is
experimentally and numerically investigated. Based on the robust chaos synchronization between two authorized SLs,
0.5Gbits/s pseudo-random data bidirectional message transmission between the two SLs has been preliminarily realized
experimentally. Moreover, related theoretical simulations are also given, which basically conforms to our experimental
observations.
We present a low crosstalk, low losses crossings for silicon-on-insulator waveguides by choosing the optimum crossing angle. The waveguides are broadened using a 3 μm parabolic taper in each arm. It is obtained that by using the crossing angles of 60 deg instead of the conventional 90 deg crossing angle, crosstalk losses are improved by more than 3.7 dB without degrading transmission losses. The transmission behavior of the crossing waveguides are illustrated by numerical simulations through the finite difference time domain method. The proposed crossing structure has a high compactness, a broad bandwidth with almost flat transmission losses, and constant crosstalk losses.
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