宽频带光纤耦合器的近似模型和实验验证

A SIMPLE MODEL AND EXPERIMENT FOR THE WIDE FREQUENCY BAND OPTICAL FIBER COUPLERS

本文用理论分析证明了将单模光纤耦合器的腰部熔锥区域简化成等效平行波导的近似模型必须作弱导近似和弱耦合近似，并在实践上用弱熔锥工艺制成了宽频带单模光纤耦合器，对该器件有关参量和尺寸的测量及计算，表明具有哑铃形腰部横截面结构的宽频带熔锥型耦合器的组合波导满足弱导近似和近似条件，用等效平行波导的近似模型计算耦合器转换功率随波长变化的曲线，不仅宽频带特性的理论曲线与实验符合得好，而且耦合器的耦合特性对二光纤芯径比及熔锥长度变化十分灵敏，这也是与实验相符。

We proved theoritically the weakly guiding and weakly coupling approxima-tion must be utilized when our approximate te parallel waveguids model takes the place ofthe original model of the fused tapered wide band couplers According to the experimenton the weakly fused tapered couplers development by ourself we obtain that the fusedtapered wide band couplers with a shape of dumbbell satisfied the weakly guiding and weakcou plers conditions.And further according to the curve of the translation power versusthe wavelength,we obtained that not only the theoritical curve reflecting the wide-band. characteristic was match well to the experimen t curve but all so it was identical to thepmctical result that the coupling characteristic was much sensitive about the couplinglength.