高频CO2激光脉冲写入的超长周期光纤光栅

研究了周期为3 mm的超长周期光纤光栅(ULPFG)各谐振峰的温度和应变特性，报道了用高频CO2激光脉冲写入的周期可达数毫米的包层折变非对称分布的ULPFG.该光栅各谐振峰由不同阶次闪耀模与纤芯基模同向耦合而成，理论和实验表明不同阶次谐振峰对外界参数如温度、应变等变化具有不同的灵敏度，因此这种ULPFG可望用于多参数同时测量中.

Ultra-Long Period Fiber Gratings Written by High-Frequency CO2 Laser Pulses

Novel ultra-long period fiber gratings (ULPFGs) with periods of up to several millimeters, which were written by the high-frequency CO_2 laser pulses,were reported.The refractive index change occured mainly within the cladding area of the fiber and had an unsymmetrical distribution on the cross-section of the ULPFG.The resonant loss peaks of the ULPFG were generated from the coupling of the forward propagating core mode to the cladding modes of fundamental and harmonic orders.Such a ULPFG can be used to measure multi-parameters simultaneously as these resonant loss peaks have different sensitivities to temperature,strain,bending and torsion,et al.The temperature and strain characteristics of the ULPFGs with 3 mm period were investigated by experiment.Meanwhile,several new approaches of the potential applications of the ULPFG were proposed.