An Ant Colony Algorithm Based on Cross-Layer Design for Routing and Wavelength Assignment in Optical Satellite Networks

This paper introduces an ant colony routing and wavelength assignment algorithm based on cross-layer design(CL-ACRWA),which can overcome the adverse effects of Doppler wavelength shift on data transmission in optical satellite networks. Firstly, a cross-layer optimization model is built, which considers the Doppler wavelength shift, the transmission delay as well as wavelength-continuity constraint. Then an ant colony algorithm is utilized to solve the cross-layer optimization model, resulting in finding an optimal light path satisfying the above constraints for every connection request. The performance of CL-ACRWA is measured by the communication success probability, the convergence property and the transmission delay. Simulation results show that CL-ACRWA performs well in communication success probability and has good global search ability as well as fast convergence speed. Meanwhile, the transmission delay can meet the basic requirement of real-time transmission of business.

Dynamic routing and wavelength assignment algorithm of optical satellite networks based on cross-layer design

In order to overcome the adverse effects of Doppler wavelength shift on data transmission in the optical satellite networks,a dynamic routing and wavelength assignment algorithm based on crosslayer design( CL-DRWA) is introduced which can improve robustness of the network. Above all,a cross-layer optimization model is designed,which considers transmission delay and wavelength-continuity constraint,as well as Doppler wavelength shift. Then CL-DRWA is applied to solve this model,resulting in finding an optimal light path satisfying the above constraints for every connection request. In CL-DRWA,Bellman-Ford method is used to find an optimal route and a distributed relative capacity loss method is implemented to get an optimal wavelength assignment result on the optimal route. Moreover,compared with the dynamic routing and wavelength assignment algorithm based on minimum delay strategy( MD-DRWA),CL-DRWA can make an improvement of 5. 3% on the communication success probability. Meanwhile,CL-DRWA can meet the requirement of transmission delay for real-time services.

Quantum Well Intermixing of InGaAsP QWs by Impurity Free Vacancy Diffusion Using SiO_2 Encapsulation

Experiment on quantum well intermixing (QWI) of InGaAsP QWs by impurity free vacancy diffusion (IFVD) using SiO 2 encapsulation is reported.A maximum band gap wavelength blue shift as large as 200nm is realized.Furthermore,an FP laser blue shifted 21nm by QWI is fabricated with characteristics comparable with the as grown one.

Performance optimization of scintillator neutron detectors for EMD in CSNS

Chinese Spallation Neutron Source(CSNS) has successfully produced its first neutron beam in 28th August 2017. It has been running steadily from March, 2018. According to the construction plan, the engineering materials diffractometer(EMD) will be installed between 2019–2023. This instrument requires the neutron detectors with the cover area near3 m2in two 90° neutron diffraction angle positions, the neutron detecting efficiency is better than 40%@1A, and the spatial resolution is better than 4 mm×200 mm in horizontal and vertical directions respectively. We have developed a onedimensional position-sensitive neutron detector based on the oblique6Li F/Zn S(Ag) scintillators, wavelength shifting fibers,and Si PMs(silicon photomultipliers) readout. The inhomogeneity of the neutron detection efficiency between each pixel and each detector module, which caused by the inconsistency of the wave-length shifting fibers in collecting scintillation photons, needs to be mitigated before the installation. A performance optimization experiment of the detector modules was carried out on the BL20(beam line 20) of CSNS. Using water sample, the neutron beam with Φ5 mm exit hole was dispersed related evenly into the forward space. According to the neutron counts of each pixel of the detector module, the readout electronics threshold of each pixel is adjusted. Compared with the unadjusted detector module, the inhomogeneity of the detection efficiency for the adjusted one has been improved from 69% to 90%. The test result of the diffraction peak of the standard sample Si showed that the adjusted detector module works well.

Effect of radiation-induced color centers absorption in optical fibers on fiber optic gyroscope for space application

The effects of color centers＇ absorption on fibers and interferometric fiber optical gyroscopes（IFOGs） are studied in the paper. The irradiation induced attenuation（RIA） spectra of three types of polarization-maintaining fibers（PMFs）, i.e.,P-doped, Ge-doped, and pure silica, irradiated at 100 Gy and 1000 Gy are measured in a wavelength range from 1100 nm to1600 nm and decomposed according to the Gaussian model. The relationship of the color centers absorption intensity with radiation dose is investigated based on a power model. Furthermore, the effects of all color centers＇ absorption on RIA and mean wavelength shifts（MWS） at 1300 nm and 1550 nm are discussed respectively. Finally, the random walk coefficient（RWC） degradation induced from RIA and the scale factor error induced by MWS of the IFOG are simulated and tested at a wavelength of 1300 nm. This research will contribute to the applications of the fibers in radiation environments.

Variations in Electroluminescence Spectra of Organic Light Emitting Diodes Containing Bathocuproine Layer

Electroluminescence （EL） of organic light emitting diodes （OLEDs） with a configtration of ITO/TPD/BC/Alq3/Mg-Ag, where TPD, BC and Alq3 represent N, N＇-diphenyl-N, N＇-bis （3-methylphenyl）-1,1＇-biphenyl-4,4＇-diamine, bathocuproine and tris（8-quinolinolato）aluminum（III）, respectively, was investigated in comparison with the photoluminescence （PL） of the individual organic layers. The EL spectra of the OLEDs were found to be much different from the PL spectra of the component multiple layer structure. Each organic layer made its contribution to the light emitted from the OLEDs. Their individual contributions were related to the field distribution across the device, which was in turn dependent on the thickness of each organic layer and the applied bias voltages. Consequently, the EL spectra of the OLEDs were observed to vary as the relative thickness of any organic layer was changed and as the bias voltage was alternated. The variation of the EL spectra of the device resulted in the easiness of achieving variable colors emitted by the device, from blue to green, and then to near white light.

Synthesis and Performance of Titanium Organic Gel Doped with Rare Earth

White nano-titanium organic compound-gel with steady performance was synthesized by sol-gel method. This gel has good absorbency to ultraviolet rays. Specially, the absorption wavelength of the organic gel shifted from 250.9 to 254.3 nm(doped with La) and 257.8 nm(doped with Ce), respectively and the absorption peak broadened. The broadening extent has direct ratio with the doping content. It is indicated that when the thickness of the organic gel coat is 60 μm, 98.8% ultraviolet with radiation intensity of 17.2 μW·cm -2 is blocked off. The TEM test shows that the diameter of the titanium organic gel doped with lanthanum is about 5 nm and the granules are uniform. It is indicated that by X-ray this organic substance is amorphous state and it will form nano-TiO_2 with anatase structure calcined at 450 ℃.

Colorimetric Determination of Chloridion in Domestic Water Based on the Wavelength Shift of CsPbBr_(3) Perovskite Nanocrystals via Halide Exchange

Cubic phase CsPbBr_(3)perovskite nanocrystals(PNCs)was prepared by a high-temperature hot-injection method.The high photoluminescence quantum yield(PLQY)of as-prepared CsPbBr_(3)PNCs was 87%,which can be used for the determination of chloridion in domestic water samples based on their wavelength-shift characteristics via halide exchange.The proposal approach for the determination of chloridion reveals a linear correlation ranged from 10 to 200μM of the chloridion concentration and the wavelength shift of CsPbBr_(3)PNCs with a correlation coe fficient of R^(2)=0.9956.The as-mentioned method reveals neglectable responses towards those co-existing ions in the water aside from chloridion,due to the quick exchange between Cl and Br and the outstanding color change caused by wavelength shift.The strategy has been applied to the determination of chloridion in water samples with the recoveries of 98.9–104.2%and the limit of detection(LOD)of 4μM.These results show that the suggested approach is promising for the development of novel fluorescence detection for chloridion in water.

An Adjustable Pure Dispersion Slope Compensating-Module without Center Wavelength Shift Based on Strain-Chirped Fiber Bragg Gratings

We demonstrate an adjustable pure dispersion slope compensating-module based on strain-chirped fiber Bragg gratings. The center wavelength of the module is preserved while the pure dispersion slope is tuned.

Colorimetric Sensing of Hydrogen Peroxide Based on the Wavelength-Shift of CsPbBr_(3) Perovskite Nanocrystals on Water-Oil Interface

In this study,the halogen exchange reactions are investigated between KI or methylamine iodide in aqueous solution and CsPbBr_(3)NCs in toluene.The mass transfer process on the interface between water and toluene affects the halogen exchange time and e fficiency.Stirring and heating can effectively improve the halogen exchange e fficiency and increases the sensing sensitivity.The photoluminescence wavelength shift of CsPbBr_(3)NCs shows good linear relationship with the concentration of I-in the range from 0 to 20 nmol/L with the detection limit of 0.2 nmol/L I^(-).Taking H_(2)O_(2)as a typical water-soluble oxide,the method is applied to the colorimetric sensing of H_(2)O_(2)in water solution.After the optimization of sensing conditions,the obvious wavelength shift could be observed with the different concentration range of H_(2)O_(2).A good linear relationship between the wavelength shift and the H_(2)O_(2)concentration from 0 to 1.0 mmol/L with the detection limit of 0.05 mmol/L H_(2)O_(2)could be found.

Study of a position-sensitive scintillator neutron detector

The investigation of a novel thermal neutron detector is developed to fulfill the requirements of the high intensity power diffractometer （HIPD） at the Chinese Spallation Neutron Source （CSNS）. It consists of two layers of 6LiF/ZnS（Ag） scintillators, two layers of crossed WLSF arrays, several multi-anode photo multiplier tubes （MA-PMT）, and the matching readout electronics. The neutron detection efficiency of the scintilltors, the light transportation ability of the WLSF, and the spatial linearity of the readout electronics are measured and discussed in this paper. It shows that the sandwich structure and the compact readout electronics could fulfill the needs of the HIPD. A prototype with a 10 cm×10 cm sensitive area has been constructed to further study the characteristics of the neutron scintillator detector.

Tuning plasmon absorption of unmodified silver nanoplates for sensitive and selective detection of copper ions by introduction of ascorbate

Silver nanoplates as novel optical sensors for Cu^2＋ detection have been demonstrated.Silver nanoplates are synthesized via previous H_2O_2-NaBH_4 cyclic oxidation-reduction reactions.With introduction of ascorbate as mild reductants,Cu^2＋ ions are reduced into Cu~＋ and the Cu^＋ is further reduced to Cu,which is deposited on the surface of the silver nanoplates.The deposition of the Cu on the surface of the silver nanoplates allows a significant red-shift of their plasmon absorption.Therefore,trace Cu^2＋ can be detected.The shift of the plasmon absorption wavelength of silver nanoplates is proportional to the Cu^2＋concentration over a range of 40-340 μmol L^（-1） with a limit of detection of 9.0 μmol L^（-1）.Moreover,such silver nanoplate-based optical sensors provide good selectivity for Cu^2＋ detection,and most other metal ions do not disturb its detection.Moreover,the practicality of the proposed sensor was tested.This Cu^2＋assay is advantageous in its simplicity,selectivity,and cost-effectiveness.