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- 摘要
- 关键词
- 实验方案
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Performance of Dispersion-Reduced Wavelength Assignment in Wavelength-Routed Optical Networks
摘要： This paper analyses the performance of the dispersion-reduced wavelength assignment (DRWA) scheme in wavelength-routed optical networks. The signal quality degradation due to the dispersion effect in longer lightpaths is higher than that of shorter lightpaths in a dispersion uncompensated network. DRWA assigns the longer distance lightpath requests to the wavelengths having a lower dispersion effect, and the wavelengths having a higher dispersion effect are allocated to the shorter distance lightpath requests. Thus, the signal quality of longer lightpaths is maintained. As a result, blocking of longer lightpath requests due to the dissatisfaction of signal quality is reduced. Simulation results show that the DRWA scheme suppresses the blocking probability and improves the traffic admissibility compared to the conventional schemes.
关键词： wavelength-routed optical networks,and blocking probability,dispersion,signal quality
更新于2025-09-11 14:15:04
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Impact of depth-dependent optical attenuation on wavelength selection for spectroscopic photoacoustic imaging
摘要： An optical wavelength selection method based on the stability of the absorption cross-section matrix to improve spectroscopic photoacoustic (sPA) imaging was recently introduced. However, spatially-varying chromophore concentrations cause the wavelength- and depth-dependent variations of the optical fluence, which degrades the accuracy of quantitative sPA imaging. This study introduces a depth-optimized method that determines an optimal wavelength set minimizing an inverse of the multiplication of absorption cross-section matrix and fluence matrix to minimize the errors in concentration estimation. This method assumes that the optical fluence distribution is known or can be attained otherwise. We used a Monte Carlo simulation of light propagation in tissue with various depths and concentrations of deoxy-/oxy-hemoglobin. We quantitatively compared the developed and current approaches, indicating that the choice of wavelength is critical and our approach is effective especially when quantifying deeper imaging targets.
关键词： Spectroscopic photoacoustic imaging,Spectral unmixing,Optimal wavelength selection,Oxygen saturation estimation
更新于2025-09-11 14:15:04
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Cu2ZnGe(S1-xSe x)4 – The challenge to synthesize single phase material
摘要： The variation of the band gap energy in Cu2ZnGeSe4 and Cu2ZnGeS4 from 1.4 eV to 1.7 eV, which is controlled by different S/(S+Se) ratios renders the Cu2ZnGe(S1-xSex)4 solid solution an interesting material for the application in multi-junction solar cells. Nevertheless, this system has a certain complexity due to the existence of different polymorphs. Cu2ZnGeSe4 crystallizes in the tetragonal kesterite type structure, whereas Cu2ZnGeS4 may crystallize in the tetragonal stannite or the orthorhombic wurtz-stannite type structure, respectively. To gain deeper insights into this complex system a systematic study of the solid solution series Cu2ZnGe(S1-xSex)4 was performed using polycrystalline material prepared by solid state reaction. The chemical analysis performed by wavelength dispersive X-ray spectroscopy showed remarkable inhomogeneities with different quaternary phases co-existing within one sample. Additionally, a wide variety of binary and ternary secondary phases as well as elemental Ge was observed. The variety of secondary phases is higher in S-rich samples than in Se-rich samples of the solid solution. Thus, synthesis of Cu2ZnGe(S1-xSex)4 mixed crystals with off-stoichiometric composition is readily accompanied by the formation of various secondary phases making it a difficult task to obtain single phase material.
关键词： Wavelength dispersive X-ray spectroscopy,Solid state reaction,Polycrystalline powders,Chalcogenides,Secondary phases,Copper zinc germanium selenide,Copper zinc germanium sulfide
更新于2025-09-11 14:15:04
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[IEEE 2018 International Conference on Smart City and Emerging Technology (ICSCET) - Mumbai, India (2018.1.5-2018.1.5)] 2018 International Conference on Smart City and Emerging Technology (ICSCET) - I. Simulation of bi-directional WDM-TDM PON with 5 Gb/s downstream and 2.5 Gb/s Upstream re-modulated Data based on RSOA
摘要： Paper present a simulation of bi-directional WDM-TDM PON with upstream re-modulation based on RSOA for 64 ONUs at 60 Km reach with 5 Gb/s downstream and 2.5 Gb/s upstream bit rate. A 1:16 splitter is used as a PON element which creates communication between central office and different users. The effectiveness of this design depends on the ability of the RSOA to re-modulate the received downstream signal with the new upstream signal. This architecture is investigated for different RSOA power, downstream receiver power and extinction ratio in terms of BER. The result shows that as the RSOA input power decreases and the device operating regime becomes increasingly linear, the BER performance of the upstream signal deteriorates and that of downstream signal improves. Also it is observed that greater the extinction ratio the harder is for the RSOA to overwrite the downstream signal
关键词： (RSOA),division multiplexing (TDM),(PON),Reflective,Wavelength division multiplexing(WDM),optical network,time-,unit(ONU),semiconductor optical amplifier,Passive optical network
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Nonlinear Hyperspectral Unmixing Via Modelling Band Dependent Nonlinearity
摘要： Wavelength dependent nonlinearity is an essential issue in hyperspectral unmixing, which was overlooked in the past. In this paper, a band-wise nonlinear unmixing method is presented. An extended multilinear mixing model is adopted for interpreting different degrees of nonlinear contributions per band. Moreover, regularizers including abundances’ sparsity and nonlinear parameters’ smoothness are exploited to formulate the optimization problem and obtain better unmixing results. Finally, unmixing is implemented in the scheme of alternating direction method of multipliers. Experimental results on both simulated and real hyperspectral data validate that the proposed method can improve the unmixing accuracy and reveal the change of nonlinearity at each band as well.
关键词： extended multilinear mixing model,nonlinear spectral unmixing,constrained optimization,Hyperspectral imagery,wavelength-wise nonlinearity
更新于2025-09-10 09:29:36
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Determination and Visualization of Different Levels of Deoxynivalenol in Bulk Wheat Kernels by Hyperspectral Imaging
摘要： A hyperspectral imaging system is proposed as a method to rapidly and nondestructively predict mycotoxin deoxynivalenol (DON) levels in FHB-infected wheat kernels. Standard normal variate transformation and multiplicative scatter correction (MSC) were used in spectral preprocessing. The successive projections algorithm (SPA) and random frog algorithm were used to select the optical wavelengths. Finally, the support vector machine (SVM) technique and partial least squares discriminant analysis were applied to establish different models for determining DON levels. Based on a comparison of the results, the MSC–SPA–SVM model, with the highest classi?cation accuracy (100.00% for the training test and 97.92% for the testing set), gave the best performance, and a visualization map of the DON content level based on this model was created.
关键词： optical wavelength selection,hyperspectral imaging,classi?cation model,deoxynivalenol content,bulk wheat kernels,visualization map
更新于2025-09-10 09:29:36
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Optical switching phenomenon in ladder type atomic system under varying wavelength mismatching effect with one due to a Rydberg transition
摘要： We present a theoretical study on probe field propagation through a three-level ? type system formed in an atomic vapor medium in presence of a strong control field. The model is based on density matrix method and is solved analytically, without neglecting any term in any power of probe and control Rabi frequencies, to find out the probe response under Doppler free condition as well as at room temperature. The probe response for a four-level ? type system is also determined analytically. Electromagnetically induced transparency is formed in the simulated probe response for both the level schemes. We also present the switching of probe field propagation from subluminal to superluminal as a function of probe detuning for different control transitions, one of which is to a Rydberg state. The switching window becomes asymmetric under detuned control field with the asymmetry depending on the wavelength mismatching factor between the control field and the probe field. Under strong probe regime probe propagation switches from superluminal to subluminal on resonance when the wavelength mismatch between the probe and the control field is increased, an effect which can be explained with the help of the analytical model that is free from any perturbative treatment.
关键词： wavelength mismatching effect,electromagnetically induced transparency,Rydberg state,optical switching,Ladder (?) type system
更新于2025-09-10 09:29:36
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A Method to Improve the Imaging Quality in Dual-Wavelength Digital Holographic Microscopy
摘要： A digital hologram-optimizing method was proposed to improve the imaging quality of dual-wavelength digital holographic microscopy (DDHM) by reducing the phase noise level. In our previous work, phase noise reduction was achieved by dual-wavelength digital image-plane holographic microscopy (DDIPHM). In the optimization method in this paper, the phase noise was further reduced by enhancing the real-image term and suppressing effects of the zero-order term in the frequency spectrum of a digital hologram. Practically, the carrier frequency of the real-image term has the correspondence with interference fringes the first order intrinsic mode function (IMF1) in bidimensional empirical mode decomposition (BEMD) has similar characteristics to the grayscale values of ideal interference fringes. Therefore, with the combination of DDIPHM and BEMD, by utilizing the characteristics of IMF1, the digital hologram was optimized with purified interference fringes, enhancing the real-image term simultaneously. Finally, the validity of the proposed method was verified by experimental results on a microstep.
关键词： digital holographic microscopy,BEMD,dual-wavelength,DDIPHM,phase noise
更新于2025-09-10 09:29:36
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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI, USA (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Hybrid multi-wavelength photoacoustic imaging
摘要： Multi-wavelength photoacoustic (PA) imaging has been studied extensively to explore the spectroscopic absorption contrast of biological tissues. To generate strong PA signals, a high-power wavelength-tunable pulsed laser source has to be employed, which is bulky and quite expensive. In this paper, we propose a hybrid multi-wavelength PA imaging (hPAI) method based on combination of single-wavelength pulsed and multi-wavelength continuous-wave (CW) laser sources. By carefully controlling laser illumination sequence (pulse-CW-pulse), and extracting the PA signals’ difference before and after heating of CW lasers, the optical absorption property of multi-wavelength CW lasers could be obtained. Compared with conventional PA imaging, the proposed hPAI shows much lower system cost due to the usage of single-wavelength pulsed laser and cheap CW lasers. Theoretical analysis and analytical model are presented in this paper, followed by proof-of-concept experimental results.
关键词： photoacoustic imaging,continuous-wave laser,multi-wavelength,pulsed laser,hybrid imaging
更新于2025-09-10 09:29:36
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Fabrication of Doubly-Corrugated Zero-Contrast-Grating for Broadband Pixelated Filtering in the Mid-IR Range
摘要： Zero-contrast grating filters (ZCG) car be used to implement efficient bandpass transmission filter with narrow bandwidths of a few nanometers. In a precedent article [1], we have illustrated the validity of the ZCG approach for the mid-IR range using germanium and calcium fluoride, as well as the possibility to increase both the bandwidth and the angular acceptance of such filters by a decade or more using a double corrugation scheme for the grating. However, when it comes to fabricating such devices, conventional semiconductor methods cannot be straightforwardly applied because of the specific requirements of the infrared materials used. Adapting specific methods of the semiconductor industry, we manage to fabricate such devices. A first optical characterization is performed.
关键词： guided-mode resonances,sub-wavelength grating,infrared,bandpass filters,fabrication
更新于2025-09-10 09:29:36