It is indicated that by optimizing the parameter of few-mode fiber,the modulation depth of FMFI can be greater than 0.98 and coupling efficiency larger than 0.5,in case of SMF-28 input and output fiber.

• 计算结果表明；在采用SMF-28作为输入输出单模光纤的情况下；通过优化设计少模光纤的参数；可以使得调制深度大于98%25；耦合效率接近于0.；5