查看更多>>摘要：Space division multiplex elastic optical networks (SDM-EONs) based on multi-core fiber (MCF) have been regarded as one of the promising solutions to address the future network capacity crunch. Inter-core crosstalk (XT) and intra-core physical layer impairments (PLI) exist in the MCF and degrade the quality of transmission (QoT) for lightpaths. Meanwhile, the establishment of new lightpaths affects the QoT of existing lightpaths due to dynamic spectrum occupancy in the network. This paper focuses on resource allocation under the constraint of physical impairment. Firstly, a dynamic impairment (DI) evaluation model is established to assess the level of impairment influence in terms of dynamic spectrum occupancy. Then, a DI-aware routing, modulation, core, and spectrum allocation (RMCSA) algorithm is proposed, which considers the influence of new lightpath establishment on existing lightpaths. Here, the core and spectrum resources with the least impact of impairment on existing lightpaths are selected preferentially to improve the QoT of lightpaths. Simulation results indicate that the proposed DI-aware RMCSA algorithm reduces the accumulated physical impairment on existing lightpaths, providing a lower probability of blocking and greater spectrum utilization.
查看更多>>摘要：3D resolution is an important display performance of integral imaging system. In this paper, an integral imaging system with improved resolution was proposed by using precise light control and error compensation. In the proposed system, a precise light control unit was used instead of the conventional diffused backlight unit, so as to reduce the voxel size. Additionally, an error compensation method was proposed to avoid the mismatch between the pitches of the lens array and the elemental image array, so as to eliminate the crosstalk of reconstructed 3D images. In the optical experiment, a prototype was developed using the proposed structure and error compensation method. It reconstructed vivid 3D images with higher resolution and less crosstalk compared to the conventional system.
查看更多>>摘要：Non-line-of-sight (NLOS) optical camera communications (OCC) is a potential wireless communication technology, which offers robustness to blocking and blooming effect, higher data throughput over longer transmission distances compared with line-of-sight OCC. In this work, we propose a wavelength division multiplexing (WDM)-multiple inputs multiple outputs (MIMO) NLOS OCC system with multi-level pulse width modulation (MPWM) and difference-based pulse width recognition (DBPWR) schemes. Signals on different color channels are separated through the RGB filter of the CMOS camera, while MPWM signals on the same color channel are separated using the DBPWR algorithm. Compared with the conventional threshold-based demodulation scheme, the proposed DBPWR scheme has lower complexity, higher reliability, and improved sampling frequency offset tolerance. A total data rate of 10.8 kb/s is experimentally demonstrated over more than 2 m NLOS link using the proposed WDM-MIMO OCC system, which is sufficient in many Internet of things applications.
查看更多>>摘要：In this paper, the loosely bound state pulses are obtained in a passively mode-locked Er-doped fiber laser (EDFL). The microfiber-based two-dimensional In2Se3 nanosheets with a low modulation depth of-0.48% is chosen as the saturable absorber (SA), which is beneficial to generate bound state soliton. When the pump power increases from 83 to 450 mW, the number of the bound state soliton varies from 16 to 337, which can be attributed to the balance between the attraction from the dispersive wave (DW) and the repulsion from the gain-absorption depletion and recovery (GADR). Moreover, a subsequent theoretical simulation is also carried out to further demonstrate the experimental phenomena. In addition, the internal dynamics of pulse generation is deeply studied, which is of great significance for further understanding the bound state pulses.
查看更多>>摘要：Here, a novel family of stochastic electromagnetic sources called spatiotemporally partially coherent partially polarized multi-Gaussian Schell-model vortex pulsed beams is proposed. With the extended Huygens-Fresnel principle, we derive the analytical formulas for the propagation of our beam in atmospheric turbulence. The spectral density and spectral degree of polarization of such beam both in free space and atmospheric turbulence are investigated. For comparison, we also study the behavior of the partially polarized multi-Gaussian Schell-model non-vortex pulsed beams during transmission. Our theoretical models enrich the classical theory of propagating stochastic electromagnetic beams and may provide a feasible method for further explorations to the novel kind of optical field modulation.
查看更多>>摘要：The effect of source coherence on the average signal-to-noise ratio ((SNR)) performance of free space optical communication (FSOC) systems operating in weak atmospheric turbulence is investigated with the help of the extended Huygens-Fresnel principle. For an FSOC system that uses a partially coherent laser source, first, the received power at the finite-sized receiver aperture is derived. Then, the power scintillation index is evaluated that reflects the aperture averaging. Using these derived optical entities, the variations of (SNR) are examined versus parameters such as the degree of source coherence, wavelength, link distance, source size, structure constant of atmosphere and the receiver aperture radius. Obtained results show that a decrease in the degree of source coherence has a positive effect on (SNR).
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