提出了一种光照直接改变光纤布拉格光栅(FBG)直流折射率调制强度引入相移的方法。仿真和实验表明,利用该方法可以在FBG上产生任意相移量。对利用该方法设计的相移FBG和传统离散相移FBG的性能进行了比较,表明两者具有相近的反射谱特性。针对光码分多址应用,制作了7位、63位码片的时域相位编解码器,测试结果表明其具有良好的编解码性能,从而证明了该种方法可用于制作多相移光栅。该方法在FBG中引入相移时不需要相位掩模板、制作工艺精度低,因此在灵活性、简单性和制作成本方面有一定的优势。 A method is proposed to directly change the modulation index of DC refraction index in fiber Bragg grating (FBG) by illumination. Simulation and experiment show that this method can generate any phase shift in FBG. The performance of the phase-shifted FBG and the traditional discrete phase-shifted FBG designed by this method are compared, which shows that the two have similar reflectivity characteristics. For optical code division multiple access applications, time-domain phase coders of 7-bit and 63-bit chips are fabricated. The test results show that they have good codec performance, which proves that this method can be used to produce multi-phase shift grating. This method does not require a phase mask when phase shift is introduced into the FBG. This method has low fabrication accuracy and therefore has certain advantages in terms of flexibility, simplicity and manufacturing cost.