双面曝光长周期光纤光栅偏振相关损耗

研究了采用高频CO2激光脉冲通过单面和双面曝光制作出的长周期光纤光栅(LPFG)的偏振相关损耗特性。单面曝光制作的长周期光纤光栅由于光纤横截面折射率改变不均匀,对入射光偏振态有较强的依赖性,主要表现为偏振相关损耗较大;为了降低偏振相关损耗,在制作长周期光纤光栅的过程中采用双面曝光的方法,以使其横截面折射率调制受高频CO2激光曝光改变均匀。实验数据显示,高频CO2激光脉冲制作的普通单面曝光长周期光纤光栅最大偏振相关损耗高达1.24 dB,而采用双面曝光的相同谐振峰值长周期光纤光栅的偏振相关损耗则可降至0.42 dB。因此,双面曝光制作的长周期光纤光栅能较好地克服入射光偏振态的不良影响,从而满足对偏振敏感的光纤通信和传感系统的应用要求。

Polarization-Dependent Loss of Long-Period Fiber Grating Fabricated by Dual-Side Exposure Method

The polarization-dependent loss(PDL) of long-period fiber gratings(LPFGs) etched by high-frequency CO2 laser pulses through single-side and dual-side exposure technologies was investigated.Long-period fiber gratings induced by the single-side exposure method depend greatly on the polarization state of incident light and have large polarization-dependent loss due to the asymmetry of refractive index profile in its cross section.A new dual-side exposure method is applied in long-period fiber gratings writing process to reduce polarization-dependent loss by uniforming the refractive index profile in the fiber cross section.Experimental results show that polarization-dependent loss of the long-period fiber gratings drops down to 0.42 dB by using dual-side exposure technology compared with 1.24 dB by the single-side exposure method.The dual-side exposure technique overcomes the influence of polarization state of incident light and can produce low-polarization-dependent loss long-period fiber gratings which can be widely used in optical fiber communication and sensing systems.