均匀光纤布拉格光栅的反射偏振相关损耗特性

Characterization of Polarization Dependent Loss in Reflection in Uniform Fiber Bragg Gratings

研究了单模光纤布拉格光栅的偏振相关损耗(PDL)特性。运用耦合模理论和琼斯(Jones)矩阵提出了反射光的有效偏振相关损耗(PDLeff),并模拟了其随光栅参数和双折射量的变化性质。光栅反射光的偏振相关损耗在反射谱的带边处明显地表现出来,特别是带边比较陡峭时。结果表明,光栅的有效偏振相关损耗明显地依赖于光栅的结构参数和双折射量。光栅的有效偏振相关损耗随光栅长度和调制深度的增加急剧增大。对于给定光栅长度和调制深度的光栅,光栅双折射量小于2×10-5时,光栅的有效偏振相关损耗随双折射的增大迅速增大;光栅双折射量大于2.5×10-4时,光栅的有效偏振相关损耗的两个主峰的宽度变大并在其上有子峰,随双折射的继续增大,两主峰间距增大而子峰变小。实验结果与理论模拟基本吻合。

Wavelength dependency of polarization dependent loss（PDL） in reflection in uniform fiber Bragg gratings（FBG） written in single-mode fibers（SMF） is studied deteriledly.Effective PDL（PDLeff） and simulations are carried out using the coupled-mode theory and the Jones matrix.The evolution with wavelength of PDLeff as a function of the grating parameters and the birefringence value is analyzed.The PDLeff appears clearly on the band edges of the reflection spectrum,especially with the steep sides.Numerical results demonstrate that the PDLeff evolutions with wavelength can be strongly enhanced by a modification of the grating parameters.With increase of grating length and modulation depth,the PDLeff rapidly increases.For a given grating length and modulation depth of the grating,when grating birefringence is less than 2×10^-5,the PDLeff increases rapidly with the increase of birefringence.As birefringence is greater than 2.5×10^-4,the two main peaks with sub-peaks on it of the PDLeff become greater.With birefringence continuing increasing,the distance between the two main peaks increases,and the sub-peaks on the main peaks become smaller.They are presented a complete characterization of PDLeff in FBG and a good agreement between theory and experiment is got.