不等带宽奇偶交错滤波器设计

Design of Different Bandwidth Interleaver

为了在10 Gb／s+40 Gb／s混合系统中提高奇偶交错滤波器的带宽利用率,采用光格型有限冲激响应 (FIR)模型在z变换域对耦合器级联形式的光滤波器进行了理论分析．用MATLAB软件的信号处理工具箱Sptool 在z域将偶信道设计成通带阻带宽度比为7:3低通滤波器,用于传输40 Gb／s信号,由对称性可知奇信道为通带阻带宽度比为3:7的高通滤波器,用于传输10 Gb／s信号．所设计的不等带宽奇偶交错滤波器由33个不同分光比的耦合器构成,两个输出端口的3 dB带宽分别为70．80 GHz和29．20 GHz,隔离度大于35 dB,通带纹波小于0．001 dB,且具有类似矩形的幅频响应特性．该滤波器较传统的等带宽50 GHz奇偶交错滤波器有更高的带宽利用率,在 10 Gb／s向10 Gb／s+40 Gb／s升级过程中作为复用-解复用器具有很大优势．

To improve the utilization efficiency of interleaver bandwidth in 10 Gb/s plus 40 Gb/s hybrid system, the cascaded coupler optical filter is theoretically analyzed by optical lattice finite impulse response （FIR） model in z domain in this paper. The even channel lowpass filter is designed and the ratio of passband to stopband bandwidth is 7：3 in order to transmit 40 Gb/s signal in z domain by MATLAB software. As a result of symmetry, the odd channel highpass filter of which the ratio of passband to stopland bandwidth is 3：7 can transmit 10 Gb/s signal. The different bandwidth interleaver, which is designed by the method of this paper, is composed of 33 couplers with various coupling ratio. One bandwidth of the output ports at 3 dB is 70.80 GHz, and the other is 29.20 GHz. Its isolation is more than 35 dB. Its ripple is less than 0. 001 dB. Furthermore, this kind of interleaver possesses homologous rectangular amplitude frequency response characteristics. The utilization efficiency of interleaver bandwidth is higher than that of the traditional interleaver bandwidth in 50 GHz. The kind of interleaver has more advantages as muhiplexer/demuhiplexer during upgrade from 10 Gb/s to 10 Gb/s plus 40 Gb/s.