长周期保偏光纤光栅的偏振特性研究

Study of Polarization Characteristic of Long-Period Fiber Grating Written in Polarization Maintaining Fiber

用高频CO2激光脉冲写入法在熊猫保偏光纤上写入长周期光纤光栅,并对其偏振特性进行了全面的试验研究·试验结果表明,在输入椭圆偏振光偏振角度0到2π的变化范围内,高频CO2激光脉冲写入法在熊猫保偏光纤上写入的长周期光纤光栅谐振峰幅值会随着入射椭圆偏振光偏振角度的改变发生以π为周期的周期性变化,并且相邻两谐振峰幅值变化趋势相反,相位差为π.在相同偏振角度下将两谐振峰幅值相减,其差值呈近似于锯齿波的周期性变化,周期也为π·在没有发生模式干扰的情况下,谐振峰波长几乎没有发生漂移·基于模式耦合理论,文中还对所观察到的试验现象进行了定性的理论解释·

Long-period fiber grating （LPFG） written by high frequency CO2 laser pulses in panda polarization maintaining fiber was proposed, and its polarization characteristic was generally studied by experiments. The experiment results show that the resonant amplitude of LPFG changes periodically with a period of π when the polarization angle of incident elliptical polarization light varies from 0 to 2π. The amplitude change directions of two adjacent resonants were opposite with a phase difference of π and the amplitude difference of them in the same incident polarization angle varied periodically as a zigzag wave also with a period of π. The resonant wavelengths of LPFG hardly varied when there was no mode disturbs. Based on mode couple theory,the experiment results were explained qualitatively in this paper.