基于双耦合器的平坦型全光纤波长交错滤波器

All-fiber flat-top interleaver based on double single mode couplers

提出了由一个3×3单模光纤耦合器和一个2×2单模光纤耦合器级联组成的波长交错滤波器,给出了其基本结构形式。将3×3耦合器中的两边两个输出端口连接在一起,中间端口为反射回路,形成一个3阶级联反射式Mach-Ze-hnder干涉仪,利用傅里叶级数展开的方法对其输出特性进行了分析。分析结果表明:组成滤波器的两个耦合器分光比和干涉臂的臂长差取一些定值时,可得到输出波形通带平坦的波长交错滤波器,其输出稳定性和隔离度均得到了提高。与通常的3阶级联Mach-Zehnder干涉仪相比,耦合器数目减少,在实际制作时可以对耦合器的分光比和干涉臂臂长差进行准确监测和控制。

The transmission function of a interleaver consisting of a 2 × 2 and 3 × 3 single mode fiber coupler in series was analyzed. Based on the Fourier series digital approximation method, the relationship among the splitting ratios of the couplers, the length difference of interference arms and intensity transmission spectrum was discussed. The results indicate that this configuration can achieve an approximate rectangular wavelength response when the length difference of interference arms and coupling coefficients of the couplers are given by a certain value in order, its stability and isolation is improved greatly. An advantage of this,interleaver is that the coupling ratio of coupler and the proportion of the length differences can be controlled accurately because light interference effect can be sheered away in fabricating. A novel structure of interleaver is fabricated with fused biconical taper technics in experiment. The experiment results are in good agreement with the theoretical analysis.