Some factors were analyzed that thermal emissivity of gray-body were brought change in this paper such as wavelength and temperature and absorbing spectrum and emissive spectrum and the surface characteristic in flame. Based on the thermal radiation theory of gray-body, the emissivity function theoretic model of the burning object was presented. Different approximation schemes were adopted according to the property of combustion production, the
equation was set up in combustion field. The influence of the measuring temperature accuracy to the emissivity precision
was developed in flame. The results shows the object in flame can be divided into three kinds of gray body, the
correlative emissivity variable need adopt different approximation technique, a method for temperature and emissivity
measurement by multi-wavelength can improve efficient the measuring precision.
Modulational instability (MI) of electromagnetic waves in nonlinear birefringent step-wise decreasing fiber with co-existence
of cubic and quintic nonlinearity is investigated by the coherently coupled nonlinear Schrödinger equation. The
properties of MI gain are studied. The results show that, the procedure occurred not only in the normal dispersion
regime but also in abnormal dispersion regime. The positive quintic nonlinearity index intensifies the modulation
instability, making the width of the gain spectra of MI become wider and the peak gain higher, otherwise, suppresses
the modulation instability, MI gain changes according to the distance propagated, and the gain spectra will change with
token distance series.
We report on the properties of light transmission in one-dimension photonic crystals with defects of nonlinear dielectric material, photonic crystals have simple and complex period dielectric structure with multi-unit layer. In particular, we are interested in the transmittance of defect mode and the intensity enhancement factor of localized light. By the transfer-matrix method, we can calculate the electromagnetic waves transmission through a photonic crystal, the intensity enhancement factor of localized light can be obtained. The method calculated the transmission properties normal incident on a finite thickness slab of material. The numerical calculation shows that the transmission with defect layer of nonlinear dielectric material can induced to bring about change by the input intensity of light, and the change of the transmission shows the bistability. For simple and complex period dielectric in PC, if the threshold of input intensity be satisfied, the properties should be emerged easier. For complex period dielectric in PC, the transmission can show the property of complex results. When the total transmission is big, the bistability is also displayed. In addition, the character is seen to determine by the saturation absorption coefficient of the defect medium, the refractive index ratio and the number of layers.
The dispersion and self phase modulation is two important factors of the limit transmission distance in optical fiber communication. A novel method for measuring the dispersion slope of a long single-mode fiber was reported. By asymmetric modulation and Mach-Zehnder interferometer, the interferometer causes counter propagating wave to travel in test fiber with different propagation constants. We introduced the fast Fourier transform technique, the autocorrelation function is brought forward, and the information of the interference fringe is analysis with high speed so that the accuracy of signal is estimated. Successively, the experiment was performed on the test fiber to determine the nonlinear refractive index and self phase modulation, exact pulse bandwidth solution is presented. We found that
quantity was depends on the intensity of incidence light and the peak power, and the frequency spectrum is broadening clearly. The result shows that the intensity input and the peak power can affect the phase shift value.