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Simultaneous measurements of temperature and pressure with a dual-cavity Fabry-Perot sensor
摘要： A fiber-optic dual-cavity Fabry-Perot interferometric sensor for the simultaneous measurement of temperature and pressure is proposed and experimentally demonstrated. The sensor cascades a fiber-optic intrinsic Fabry–Perot interferometer (IFPI) and an extrinsic Fabry–Perot interferometer (EFPI). The IFPI is used as the temperature sensor and the EFPI is used as the pressure sensor. The pressure sensor is based on a diaphragm-free structure, and can work stably at high temperature. Two optical path differences are interrogated simultaneously by using the fast Fourier transform-based white-light interferometry and the peak-to-peak method. Experimental results show that the proposed sensor exhibits a temperature sensitivity of 29.63 nm/°C within the temperature range of 40-1100 °C, and a pressure sensitivity of 1465.8 nm/MPa within the pressure range of 0-10 MPa at the room temperature.
关键词： pressure measurement,femtosecond laser micromachining,fiber optics sensors,Fabry-Perot interferometers,temperature measurement
更新于2025-09-04 15:30:14
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Heat Resisting Metallic Meta-Skin for Simultaneous Microwave Broadband Scattering and Infrared Invisibility Based on Catenary Optical Field
摘要： Metallic skins are widely used in practical engineering owing to their inherent advantages in mechanical and physical characteristics. In this paper, a metasurface skin composed of subwavelength metallic gratings with space-variant orientations has been proposed to realize exotic electromagnetic properties in microwave and infrared regimes. Equivalent circuit theory and transfer matrix method have been adopted to quantitatively describe the optical fields and dispersion with high accuracy in a catenary form. Based on these analyses, broadband and wide-angle radar cross-section (RCS) reduction for microwave has been simulated and experimentally demonstrated. Additional characteristics such as high temperature resistance and low infrared thermal emission are also verified. It is believed that these results may provide a new platform to achieve multifunctional electromagnetic devices and are promising for many applications.
关键词： scattering,catenary optics,metasurface,thermal emission,all-metal metasurfaces
更新于2025-09-04 15:30:14
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Hafnium Sulfide Nanosheets for Ultrafast Photonic Device
摘要： Group IVB transition metal dichalcogenides (TMDs) have attracted significant interests in photoelectronics due to their predictable superior physical properties compared to group VIB (Mo and W) TMDs. However, the nonlinear optical properties and ultrafast photonic devices based on group IVB TMDs remained unexplored so far. Herein, the nonlinear optical absorption of HfS2 nanosheets (NSs) prepared by liquid exfoliation is demonstrated. The usage of HfS2 as a new ultrafast photonic device for high-energy and ultrashort pulse generation in a fiber laser is reported for the first time. A photonic crystal fiber (PCF) assisted deposition method is presented for the fabrication of an HfS2-microfiber integrated saturable absorber (SA) device with precisely controllable light–matter interaction, which can benefit the output of the device. The HfS2-microfiber SA device shows modulation depth of 15.7% and exhibits outstanding ultrashort pulse generation performance with pulse duration of 221.7 fs in the communication band. The experimental results suggest that HfS2 presents highly nonlinear optical absorption and can be developed into an excellent candidate of SA devices for the development of HfS2-based ultrafast photonics.
关键词： nonlinear optics,hafnium sulfide,ultrafast photonics
更新于2025-09-04 15:30:14
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Numerical simulation of light propagation in metal-coated SNOM tips
摘要： Presented are the results of numerical simulations accomplished to investigate the propagation of electromagnetic excitations in certain types of metal-coated tapered tips terminating SiO2 multimode optical fibres with a subwavelength output aperture. The numerical simulations were initiated in order to enable better interpretation of previously reported experimental results concerning some features of the mesoscopic effect of spectral modulation observed for a broadband light transmitted by such tips. This effect occurs due to the interference between a small number of waveguide modes exiting a metal-coated tip, and the experimental results indicate a possible mode-selective photon-plasmon coupling in the studied tips. To match the experimental conditions, the tips were modelled for the light wavelength of 800 nm as three-layer systems (with the intermediate adhesion Cr layer and the outer layer of Al or Au). However, due to computational restrictions the end of a tip, only 18 μm long (most significant), was modelled. Numerical simulations yielded the dependences of propagation and attenuation constants on the fibre core radius for the most intensive (both photonic and plasmonic) output modes. The pairs of modes most probably contributing to the observed spectral modulation were identified. Although the simulations did not reveal any explicit mode coupling, the imperfections of real tips can cause mode transformations implying possible involvement of more than two modes. The thin (20 nm) Cr layer plays the main role for plasmonic modes generated on its SiO2 interface, which explains the small outer metal layer influence on the observed modal dispersion.
关键词： numerical simulation,multimode optical fibre,optics,spectral modulation,SNOM tip,plasmonics,photonics
更新于2025-09-04 15:30:14
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Performance Analysis of Hybrid RF/FSO System using BPSK-SIM and DPSK-SIM over Gamma-Gamma Turbulence Channel with Pointing errors for Smart City Applications
摘要： The in wireless communication -Free space optics (FSO) offers lots of merits over radio frequency (RF) links due to its license free bandwidth, ease of installation, high security features, and viable cost for short distance communication. It's high speed data rate and immunity against Electromagnetic Interference (EMI) makes FSO the emerging technology of today. But, FSO is not always reliable especially during Atmospheric conditions like fog, rain, mist and snow. Hence, in account a new technique of Hybrid FSO/RF, this includes advantages of both FSO and RF technologies. Through this paper intend to perform an extensive analysis of the error and misalignment effects encountered in Line Of Sight (LOS) communication. Pointing error and turbulence effects are the main drawback parameters for our analysis. For this purpose I have taken into consideration different modulation techniques-Binary Phase Shift keying-Subcarrier Intensity Modulation (BPSK-SIM), Differential Phase Shift Keying- Subcarrier Intensity Modulation (DPSK-SIM) communication system with reference to OOK Modulation. The novel expressions for outage probability and BER for both FSO and RF system are derived which uses Rician Channel and 16QAM Modulation scheme alongside Hybrid FSO/RF system for weak, moderate, strong turbulence regimes using Meijer-G Function.
关键词： Free space optics,Hybrid RF/FSO,Gamma-Gamma Channel,Atmospheric turbulence
更新于2025-09-04 15:30:14
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[IEEE 2018 Iranian Conference on Electrical Engineering (ICEE) - Mashhad (2018.5.8-2018.5.10)] Electrical Engineering (ICEE), Iranian Conference on - An Efficient Method for Calculation of Physical Optics Integral for Large Reflector Antennas
摘要： In this paper, an efficient and very fast method for analyzing electromagnetic wave scattering from a smooth shaped PEC has been presented. The idea of this paper is based on using a powerful Gauss-Legendre quadrature technique and simultaneously mapping the 3D Physical Optics integral to 2D integral. This idea leads to a more accurate and less time-consuming algorithm due to avoiding surface meshing and 3D numerical integration.
关键词： physical optics,large reflector antenna,Gauss-Legendre quadrature
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Low-pass Frequency Selective Surface for a Dual-band Gyro-multiplier Characterized by THz-TDS
摘要： This work investigates the performance of a low-pass frequency selective surface (FSS) fabricated from perforated hole array on a copper plate for the use in a dual-band high power gyro-multiplier. The output beam from the high power gyro-multiplier contains signals at two separating bands carrying peak power up to 2 kW. The frequency separating components therefore are required to stand high power and produce low insertion loss. Metallic perforated array is an ideal option to meet these requirements. Considering the fabrication accuracy, low-pass FSS is selected. The fabrication of the low-pass FSS is based on precision milling technology. The performance of the FSS is evaluated using a terahertz time domain spectroscopy.
关键词： gyro-multiplier,terahertz time domain spectroscopy,quasi-optics,frequency selective surface
更新于2025-09-04 15:30:14
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Advanced Digital Signal Processing for Reach Extension and Performance Enhancement of 112Gbps and beyond Direct Detected DML-Based Transmission
摘要： 112Gbps per wavelength, amplification free (PAM-4) Four-level Pulse Amplitude Modulation transmissions are experimentally demonstrated with advanced digital signal processing (DSP) algorithms. Two DSP architectures are investigated for Directly Modulated Lasers (DMLs): (1) the regular DSP with Feed Forward Equalization (FFE) and Decision Feedback Equalization (DFE), and (2) the enhanced DSP with Maximum Likelihood Sequence Estimation (MLSE) equalizer. The experimental results show that with advanced DSP technologies the conventional DML can achieve 40km transmissions with Bit Error Rate (BER) under 2.4×10-4 that meets RS (544, 514) Forward Error Correction (FEC) requirement; with regular-DSP the advanced DML can achieve 40km transmissions with BER under 3.8×10-3, with stronger FEC. 112Gbps and beyond per lambda DML based transmission is a promising low power, low-cost solution for 800GbE or 1.6TbE Ethernet.
关键词： directly modulated laser (DML),semiconductor laser,fiber optics communications,Data center interconnections,digital signal processing
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Computer Tool for Simulating Frequency Modulated -Continuous Wave Radar Systems in Urban Traffic Scenes
摘要： In this work, a computer tool for the simulation of the responses of Frequency Modulated-Continuous Wave radar systems in Urban Traffic Scenes is presented. The radar echoes including frequency shifts due to distance and object speeds are computed using a new hybrid technique that combines Method of Moments, Physical Optics and Geometrical Theory of Diffraction. Arbitrarily time-shaped radar sequences can be set for obtaining output parameters like Doppler Spectrum, beat signals in frequency and time domains, distances and speeds of echoes, etc. The technique is efficient and accurate for solving the electrically large and multiscale problem that appears in the simulation of these systems in urban complex scenarios. Representative results are presented.
关键词： method of moments,FM-CW radar,hybrid methods,physical optics,geometrical theory of diffraction,anticolision,propagation,antenna,radar
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Accuracy Test of Iterative Physical Optics for Analyzing Scattering by Nonperfectly Conducting Bodies Using Impedance Boundary Conditions
摘要： An iterative physical optics has been used to analyze the electromagnetic scattering by electrically large and complex objects with nonperfectly conducting surfaces. The iterative physical optics is near-?eld corrected based on the magnetic ?eld integral equation. By comparing the scatterings computed by the iterative physical optics and multilevel fast mutipole method, the accuracy of the iterative physical optics is investigated.
关键词： magnetic ?eld integral equation (MFIE),near-?eld correction,iterative physical optics (IPO)
更新于2025-09-04 15:30:14