扭转螺旋型力学微弯长周期光纤光栅的光谱特性

Spectral characteristics of helicoidal mechanically-induced long-period fiber grating

利用两个交替放置的周期性V型刻槽板对均匀扭转后的普通单模光纤径向施力制作螺旋型力学微弯长周期光纤光栅(H-MLPFG)。通过实验研究了周期压力和扭转率对该光栅传输谱特性的影响,以及其偏振相关特性。结果表明,施加在光纤的径向压力可以改变H-MLPFG的耦合强度,但不影响其谐振波长变化,LP_(13)耦合模耦合强度在波长1 549.75nm处为30.1dB。当光纤扭转率由0增大到5.38rad/cm,LP_(11)、LP_(12)和LP_(13)模对应的扭转灵敏度分别为1.59、1.82和2.24nm/(rad·cm^(-1))。光纤扭转率为0.90rad/cm时,LP_(13)包层模具有最大偏振相关损耗,在波长1 550.45nm处偏振相关损耗约为6.86dB,对应的谐振波长分离值为1.4nm。该方法制作的LPFG模式耦合强度和谐振波长具有可调谐和可重构性的优点、且结构简单,在光纤通信和传感领域具有潜在的应用价值。

A helicoidal mechanically-induced long-period fiber grating（H-MLPFG）was formed by pressing a twisted fiber from two sides with two V-shaped identical periodically grooved plates. The influence of periodical pressure and twist rate on transmission spectrum of the H-MLPFG were investigated experimentally, together with the polarization characteristics. The results show that the depth of the coupling strength varies with the amount of pressure applied to the fiber, otherwise the resonant wavelength of the H-MLPFG is independent of it. The peak coupling strength of LP13 mode coupling is 30.1 dB at 1 549.75 nm. Twist sensitivities of the H-MLPFG is 1.59,1.82 and 2.24 nm/（radcm-1） for LP11,LP12 and LP13 mode couplings respectively when the twist rates increase from 0 to 5.38 rad/cm. The maximum PDL is approximately 6.86 dB at 1 550.45 nm for LP13 cladding mode and the corresponding resonant wavelength separation value is 1.4 nm. The H-MLPFG exhibits merits of tunable and reconstructable for coupling strength and resonant wavelength, simple and easy operation, thus has potential applications in fields of fiber-optic communications and fiber-optic sensing.