保偏光纤环与Y波导芯片直接耦合技术研究

Research on Direct Coupling of PM Fiber Coil and Y-branch LiNbO_3 Waveguide Chip

光纤陀螺光路结构中,Y波导器件与保偏光纤环通过尾纤熔接的方式连接形成闭合回路来敏感系统相对惯性空间的转动信息,而熔接点引入的偏振交叉耦合以及背向反射是制约光纤陀螺测量精度进一步提高的主要因素。为此,提出了一种实现保偏光纤环与Y波导芯片直接耦合的方法,并制作了两者直接耦合的敏感环光路。经实验测试,光路中Y波导器件的插入损耗典型值为2.7dB,分光比优于48/52~52/48,偏振串音优于-30dB,性能指标与常规的Y波导器件相当。该光路模块理论上有利于减小光纤陀螺系统噪声和提高测量精度。

In fiber optic gyroscope, Y-branch LiNbO3 waveguide device and PM（polarization maintaining）fiber coil are connected in the meaning of tail splice,thus the system performance is mainly limited by the polarization cross coupling and the back reflection induced by the splice point.Proposed is a method for realizing the direct coupling of Y-branch LiNbO3 waveguide chip and PM fiber coil by introducing two assistance alignment waveguides on the chip.Tests on the fabricated samples show that the samples can obtain the same performance as that of conventional Y-branch LiNbO3 waveguide devices with the insertion loss of 2.7dB,the split ratio of higher than 48/52-52/48,and the polarization crosstalk of better than-30 dB.The module can not only lower the noise but also improve the performance of the fiber optic gyroscope.