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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。
The polarization dependent loss (PDL) characteristics of single mode fiber Bragg gratings are investigated. The effective polarization-dependent loss (PDLeff) of the reflected light is proposed by using coupled-mode theory and Jones matrix, and its variation characteristics with grating parameters and birefringence are simulated. The polarization-dependent loss of the reflected light from the grating is evident at the band edge of the reflection spectrum, especially when the band edge is relatively steep. The results show that the effective polarization dependent loss of the grating obviously depends on the grating structure parameters and birefringence. The effective polarization-dependent loss of a grating increases sharply with increasing grating length and modulation depth. For a given grating length and modulation depth of the grating, grating birefringence less than 2 × 10-5, the effective polarization-dependent loss of the grating increases rapidly with increasing birefringence; grating birefringence greater than 2.5 × 10-4 , The width of the two main peaks of the effective polarization-dependent loss of the grating becomes larger and there is a sub-peak on it. As the birefringence continues to increase, the distance between the two main peaks increases and the sub-peak decreases. The experimental results are in good agreement with the theoretical simulation.