长周期光纤光栅波导色散因子和有效折射率热光系数的测量

对串联的长周期光纤光栅(CLPFG)的透射谱特性进行了理论分析和实验研究。分析表明，长周期光纤光栅中纤芯模和包层模之间的马赫-曾德尔干涉效应导致在长周期光纤光栅谐振峰内的梳状滤波结构特性；其峰值位置和峰间距同串联区光纤的长度以及光纤的波导色散因子有关。测量了长周期光纤光栅的透射谱，并研究了其温度特性。根据测量数据，得到对应于1554nm波长处，所用单模光纤HE14模的波导色散因子γ为0．874；纤芯／包层有效折射率差的热光系数为4．8×10^-5℃^-1。并对这一测试方法和结果，以及长周期光纤光栅的应用进

Based on the Mach-Zehnder interference effect between the core mode and the cladding modes, the interference fringes are formed by a pair of cascaded long-period fiber gratings (CLPFG). It is found that the spectral spacing and the wavelength of these fringes are related to the absolute value of waveguide dispersion factor of LPFG. So by measuring the characteristics of the transmission spectra of CLPFG, the absolute value of waveguide dispersion factor γ can be deduced. At the same time, the thermo-optic coefficient of effective refractive index μ can also be deduced by measured the thermo-effect of these fringes. By this method, at the wavelength of 1554 nm, the values of γ of HE14 cladding mode and μ are calculated to be 0.874 and 4.08×10-5℃-1, respectively.