Scattering loss in optical waveguide with trapezoidal cross section

To get the scattering loss of the trapezoidal core waveguide,a new analysis model is presented based on the perturbation equivalent method and modified effective-index method.Firstly,the trapezoidal core waveguide is successfully equivalent to the rectangular one with both restricting the same optical field energy by adopting the perturbation method,Then,the equivalent rectangular core waveguide is decomposed into two slab waveguides by employing the modified effective-index method,The trapezoidal core waveguide scattering theory model is established based on the slab waveguide scattering theory.With the sidewalls surface roughness in the range from 0 to 100 nm in the single model trapezodial core waveguide,optical simulation shows excellent agreement with the results from the scattering loss model presented.The relationship between the dimension and side-wall roughness with the scattering loss can be determined in the trapezoidal core waveguide by the scattering loss model.

Influence on Multimode Rectangular Optical Waveguide Propagation Loss by Surface Roughness

Optical scattering loss coefficient of muhimode rectangular waveguide is analyzed in this work. First, the effective refrac tive index and the mode field distribution of waveguide modes are obtained using the Marcatili method. The influence on scattering loss coefficient by waveguide surface roughness is then analyzed. Finally, the mode coupling efficiency for the SMFOpticalWaveguide （SOW） structure and MMFOptical Waveguide （MOW） structure are presented. The total scatter ing loss coefficient depends on modes scattering loss coeffi cients and the mode coupling efficiency between fiber and waveguide. The simulation results show that the total scatter ing loss coefficient for the MOW structure is affected more strongly by surface roughness than that for the SOW struc ture. The total scattering loss coefficient of waveguide decreas es from 3.97 x 10^-2 dB/cm to 2.96 x 10^-4 dB/cm for the SOW structure and from 5.24 - 10^-2 dB/cm to 4.7 x 10^-4 dB/ cm for the MOW structure when surface roughness is from 300nm to 20nm and waveguide length is 100cm.

Non-storm erosion of MeV electron outer radiation belt down to L^(*)<4.0 associated with successive enhancements of solar wind density

We report an unusual non-storm erosion event of outer zone MeV electron distribution during three successive solar wind number density enhancements(SWDEs)on November 27-30,2015.Loss of MeV electrons and energy-dependent narrowing of electron pitch angle distributions(PAD)first developed at L^(*)=5.5 and then moved down to L^(*)<4.According to the evolution of the electron phase space density(PSD)profile,losses of electrons with small pitch angles at L^(*)>4 during SWDE1 are mainly due to outward radial diffusion.However during SWDE2&3,scattering loss due to EMIC waves is dominant at 4<L^(*)<5.As for electrons with large pitch angles,outward radial diffusion is the primary loss mechanism throughout all SWDEs which is consistent with the incursion of the Last Closed Drift Shell(LCDS).The inner edge of EMIC wave activity moved from L^(*)~5 to L^(*)~4 and from L~6.4 to L~4.2 from SWDE1 to SWDE2&3,respectively,observed by Van Allen Probes and by ground stations.This is consistent with the inward penetration of anisotropic energetic protons from L^(*)=4.5 to L^(*)=3.5,suggesting that the inward extension of EMIC waves may be driven by the inward injection of anisotropic energetic protons from the dense plasma sheet.

Correlated observations linking loss of energetic protons to EMIC waves

Electromagnetic ion cyclotron(EMIC)emission is an efficient mechanism for scattering loss of energetic protons.Here,we report an event that provides both in-situ observation of energetic proton differential fluxes in the inner magnetosphere and precipitation of protons at ionospheric altitudes.During the 7-8 September 2015 geomagnetic storm the Van Allen Probes observed strong EMIC waves around L=5 and a distinct decrement in fluxes of tens of keV protons around pitch angles 0°-45°.Meanwhile,precipitating protons at ionospheric altitudes were found to significantly enhanced(by several orders of magnitude),measured by NOAA 18 and 19 when they magnetically linked to the Van Allen Probe-A.By solving the Fokker-Planck diffusion equation,we show that EMIC waves can efficiently produce loss of energetic protons within about 2 h in the pitch angle range of~0°-45°,comparable to the satellite observations.

Review of theoretical methods and research aspects for detecting leaf water content using terahertz spectroscopy and imaging

The water content in vegetative leaves is an important indicator to plant science.It reveals the physiological status of plants and provides valuable information in irrigation management.Terahertz(THz)as a state-of-the-art technology shows great potential in measuring and monitoring the water status in plant leaves.This paper reviewed the theoretical models for calculating water content in the plant leaves,the methods for eliminating the scattering loss caused by the surface roughness of leaf,the applications of THz spectroscopy and THz imaging for monitoring leaf water content and describing leaf water distribution.The survey of the researches presents the considerable advantages of this emerging and promising THz technology in agriculture.