查看更多>>摘要：? 2021 Elsevier B.V.In this paper, the geometry and aberration characteristics of von Karman conformal domes have been investigated. Based on the theory of differential geometry, the uniform formulas of curvature, which are suitable for von Karman surface, were deduced in the meridian plane and sagittal plane, respectively. According to the formula, the geometry characteristics were analyzed. By using ray tracing, the geometric aberrations and wave aberrations of the von Karman dome were obtained. Further, the aberration characteristics of the von Karman dome with different design parameters were analyzed in depth. The results showed that for the viewing angle changing from 0° to 15°, numerous aberrations, namely, defocus, astigmatism, coma, spherical, trefoil, and tetrafoil were introduced by the von Karman, whose law is similar to its geometric characteristics. The factors with a high impact on aberrations were the aspect ratio, material, and diameter of the entrance pupil.
查看更多>>摘要：? 2021Recently, benefited from the excellent capability of metasurface, the high-sensitivity THz sensing can be achieved. However, the polarization dependency and single-resonance mode still hinder the further improvement in sensitivity. In this paper, we designed a polarization-independent and multi-resonances metasurface for high-performance THz sensing. The transmission spectrum of metasurface exhibits three polarization-independent and strong resonance peaks in 0.1–2.5 THz, and all of them show high sensitivity related to ambient refractive index. The transmitted structure and polarization-independent resonance can relief the difficulty of measurement. We believe these studies will lay the theoretical and technical foundation for the design of high-sensitivity terahertz sensing.
查看更多>>摘要：? 2021 Elsevier B.V.A 100 Gbps transmitter optical sub-assembly (TOSA) based on a thin-film filter (TFF) multiplexer (MUX) demonstrated high alignment tolerance in a small volume. The model was based on the transfer-matrix method to investigate the effect of collimation and focus lens structures on coupling efficiency. The tolerances of the focus lens, MUX, and collimation lens were analyzed by simulation and experiment, obtaining the main values in 1 dB coupling loss of ±25, ±450, and ±3.3 um, respectively. Test results indicate that the transmission in a single mode fiber over 10 km is achieved with the 100 Gbps TOSA extinction ratio over 40 dB.
查看更多>>摘要：? 2021 Elsevier B.V.This paper presents a hybrid Wavelength division multiplexing-free space optics-passive optical network for bidirectional transmission with 4×10 Gbps downlink and 2×10 Gbps uplink to provide information to the wired and wireless users simultaneously over total 60 km SMF and 650 m FSO or 62 km SMF link with enhanced fault protection capability. Noise tolerance against Rayleigh backscattering (RB) also enhanced by employing two different ports of interleavers and by allowing different wavelengths of light as carrier signals for uplink and downlink transmission through a single feeder fiber. Integrated single mode fiber (SMF)/free space optics (FSO) link increase the reliability against failure of any one channel between SMF and FSO link, besides that it maintains the continuity of data transfer even where fiber link installation is restricted due to environmental boundary such as between two mountains, wide river etc. Low bit error rate (10?9), <1 dB power penalties (0.7 dB, 0.85 dB, 0.9 dB) are obtained between B2B and over total transmission link. A comparison between our proposed network and the network when the signal transmitted over total transmission link (60 km SMF+ 650 m FSO, or 62 km SMF) at a time also verified with their power budgets. Divergence losses at different FSO lengths (17 m to 680 m) are also calculated to determine the maximum possible FSO length for this proposed set up. Therefore, the proposed architecture proofs its feasibility, reliability and the capacity to continue transfer of high data rate over long distance even in the unfair environmental situation, which makes it an attractive platform to the next generation communication system (5G) to fulfill the thirst of end users.
查看更多>>摘要：? 2021 Elsevier B.V.Spatial heterodyne spectroscopy (SHS) has advantages of hyperspectral, high luminous flux, and high stability. However, its main performance indexes, such as spectral resolution, bandwidth, dynamic range and signal-to-noise ratio (SNR) are all limited by the performance parameters of the area array detector. In this paper, a digital micromirror device (DMD) is applied to the interference spectroscopy, and DMD and SHS combined modulation interference spectroscopy (DMD–SHS) is proposed. On the basis of retaining advantages of SHS such as high stability and hyperspectral resolution, DMD–SHS uses the linear array detector, eliminating high-performance area-array detector dependence and dramatically reducing the cost of the instrument. It can also improve the instrument's SNR and dynamic range, and enhance weak signals’ detection capability. DMD–SHS theory is analyzed theoretically and further verified by simulation in this paper. The combined modulation method proposed in the paper can also be applied to other interference spectroscopy, and the related research has important scientific significance and application prospect.
查看更多>>摘要：? 2021 Elsevier B.V.We propose a method to evaluate the splicing quality for few-mode fibers. A fusion fault detection system for few-mode fiber has been constructed, using OTDR technology, combined with photon lanterns as a multiplexer and a demultiplexer. Every single spatial mode is launched into the few-mode fiber under test through the mode coupler, and the power loss of each mode at the fiber fusion splice is estimated by the Rayleigh backscattering light power of the mixed mode and the single mode. The experimental results indicate that it is necessary to evaluate accurately the splicing quality of a few-mode fiber by all modes that can be transmitted in the fiber under test, rather than by a single mode.
查看更多>>摘要：? 2021Mantis shrimps can recognize polarization states that are invisible to human eyes. Inspired by its polarization vision, we propose a simple micro-nano integrated structure including a metasurface array with diamonds overlapped partially, and metal wire grids. Here, because of the asymmetry of the designed nanostructure, the device is sensitive to polarized light. The consistency between the results of FDTD simulations and our theoretical derivation shows that the design can effectively distinguish the rotation of circular polarizations by achieving differential detection of circular polarization states. The design differs from the common single-layer metasurface, achieves higher extinction ratio while maintaining a high transmittance. Especially, the peak of extinction ratios up to 1800 in the 700–1000 nm wavelength range. Therefore, the advantages of the design are enabling applications requiring high resolution and precision such as polarization detection and imaging, biomedical diagnosis, and weak magnetic detection.
查看更多>>摘要：? 2021“Comparison of the optical properties of undoped and Ga-doped ZnO thin films deposited using RF magnetron sputtering at room temperature”, Do-Hyun Kim et al., Optics Communications 281 (2008) 2120–2125. The editors would like to note that concern has been raised about the mentioned article, in which material appears to have been duplicated, without attribution, from the earlier published articles listed below. Japanese Journal of Applied Physics, Vol. 47, No. 1, 2008, pp. 87–90 Applied Science and Convergence Technology, Vol. 16, No.5, 2007, pp. 359–365 Journal of the Korean Physical Society, Vol. 51, No. 6, 2007, pp. 1987–1992 The reproduction of material without appropriate attribution is considered to be a serious breach of scientific ethics.
查看更多>>摘要：? 2021 Elsevier B.V.A 10-Gb/s data transmission using the optical physical layer encryption and quantum key distribution (QKD) is developed. The physical layer encryption basing on the spectrum phase encoding technology, and the quantum key distribution relying on optical intensity modulation (IM) Y-00 cipher, are together performed to secure optical transmissions at 10 Gb/s. Especially, We propose a quantum key distribution method in which the encryption key generated at a update rate of up to 10 MHz is used for the parameters of the physical layer encryption with the spectral phase encoding. Compared with traditional quantum key distribution, our key rate is out of reach. A 10-Gb/s secure prototype is developed basing on this technique, which is experimentally applied in the 20-channel wavelength division multiplexing (WDM) network over 100 km fiber. The experimental results show that this method can ensure reliable transmission of cooperative users and prevent information from eavesdropping. The power penalty caused by data encryption is less than 3 dB for improving security of the data transmission. Furthermore, the bit error rate (BER) is analyzed, a BER above 0.48 for eavesdropper is verified.
查看更多>>摘要：? 2021A method of holographic reconstruction under partially spatial coherent illumination with different degree of coherence is proposed to suppress speckle noise based on theoretical analysis. The core factor of speckle reduction based on partially spatial coherent light is convolution operation in CGH reconstruction process. Numerical simulations and optical experiments are both performed to verify the proposed theory. The results reconstructed by proposed and traditional method are compared, and the speckle contrasts can be reduced to 0.05 and 0.08 at most in Fresnel and Fraunhofer zone respectively. The image quality is obviously improved. This method can provide further applications for three-dimensional holographic display, beam shaping and coherence degree modulation techniques.
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