基于半带数字滤波器的马赫-曾德干涉仪型波长交错滤波器的设计

Design of Mach-Zehnder Interferometer Type Optical Interleaver Based on Half-band Digital Filter

为了改善常规马赫-曾德干涉仪型波长交错滤波器的性能,并降低光学滤波器设计过程的复杂性,将多个环形谐振腔耦合到常规马赫-曾德干涉仪的两个干涉臂上,从而可利用环形谐振腔的全通特性对光信号进行相位调制.利用数字滤波器与光学滤波器之间的相似性,将半带数字滤波器与光学波长交错滤波器相结合,设计出频谱具有对称性、通带平坦度高、精细度接近1、隔离度大于30dB的波长交错滤波器.分析表明:当微环耦合器的耦合比在10%范围内波动,或者微环的损耗系数大于0.7时,滤波器的隔离度始终高于25dB;在器件的中心波长附近,色散值接近于0.证明了所设计滤波器能够较好地适用于现有的波分复用系统.最后将多个双环谐振腔和单环谐振腔同时引入马赫-曾德干涉仪型滤波器,利用半带数字滤波器设计方法进行参数设计,计算结果表明:由双环和单环组成的复合结构的滤波器比仅仅采用多个单环的滤波器的隔离度提高约10dB.

In order to improve the function of the conventional Mach-Zehnder interferometer type optical interleaver,and to reduce the design process complexity of the optical filter,a scheme of multi-ring resonators coupled to the two interferometric arms of conventional interleaver was adopted,the ring resonator could play on signal to implement the phase modulation on light signal through utilizing the characteristics of all-pass filters.By using the similarity between the digital filter and optical filter,and combining the half-band digital filter design method and optical wavelength filter design, an interferometer was designed which has symmetrical frequency spectrum,highly flat pass band,fineness of nearly 1and the isolation of greater than 30 dB.The results indicate that,the isolation of the filter exceeds 25 dB when the coupling ratios of the micro-ring couplers fluctuate in the range of 10% or when all the loss coefficients of the micro-rings are more than 0.7;and near the center wavelength,the dispersion value is nearly to zero,which demonstrate that the filter designed by the proposed method can be applied in the dense wavelength division multiplexing system.Finally,aproject was proposed,in which multiple double-rings and single-rings are coupled in the arms of the Mach-Zehnder interferometer simultaneously.By using the design method for hald-band digital filter,the values of the design parameters can be obtained.The results indicate that for the compound structure interleaver composed by double-rings and single-rings,the isolation is increased by 10 dB than the interleaver composed only by single-rings.