Abstract
Free spectral range (FSR) of reflection spectrum of micro-ring resonator restricts the improvement in user capacity of the optical code division multiple access (OCDMA) system using micro-ring resonator array. Vernier effects can expand FSR of cascaded optical microring resonator. Based on vernier effect, a novel two-dimensional coherent optical en/decoder using serially coupled dumbbell micro-ring resonator is proposed in this paper. The theoretical model of optical transmission for series dumbbell-shaped microring resonators is established. The relation between the suppression of pseudo-modes in optical reflection spectrum and the coupling coefficient is analyzed in detail. The effects of coupling coefficient, processing error and chip rate on the performance of series dumbbell microring resonator optical en/decoder are studied. The en/decoding simulation experiments are carried out on a series dumbbell-shaped micro-ring resonator with radius of 40 μm-30 μm-40 μm respectively. The results show that comparing with the traditional series micro-ring resonator with radius of 40 μm-40 μm-40 μm respectively, the FSR value of dumbbell microcavity is increased by 4 times and the user capacity can increase exponentially. Meanwhile, the ratio of autocorrelation peak to maximum wing (<i>P</i>/<i>W</i>) and the cross-correlation ratio (<i>P</i>/<i>C</i>) are increased by about 33% and 8%, respectively.
Highlights
图 4 分别讨论了标号 1—4 伪模的峰值透射率 与 krb 的变化规律 . 图 4(a) 描述了当耦合系数 krr 为 0.02 和 0.03 时, 伪模 1 和 3 峰值透射率与耦 合系数 krb 的变化关系. 伴随 krb 的增大, 伪模 1 和 3 的峰值透射率均降低. 同时, 相同的 krb, 耦合系 数 krr 越小, 伪模抑制程度越好. 也就是说, 对于伪 模 1 和 3 而言, 较大的耦合系数 krb 与较小的耦合 系数 krr 会使伪模 1 和 3 得到良好的抑制. 图 4(b) 描述了当耦合系数 krr 为 0.02 和 0.03 时, 伪 模 2 和 4 峰值透射率与耦合系数 krb 的变化关系. 与 图 4(a) 变化趋势相反, 对于相同的 krr, 伴随 krb 的 增加, 伪模伪模 2 和 4 的峰值透射率增加. 如 krr = 0.02 时, 当 krb 变化区间在 0.3—0.7 时, 伪模 2 和 4 的峰值透射率分别增长约 15 dB 和 17 dB. 此外, 伪模 (1, 3) 的透射率明显小于伪模 (2, 4) 的峰值
3) (Key Laboratory of Opto-electronics Information Technology, Ministry of Education, School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin 300072, China)
Summary
P 根据传输方程 (1) 和方程 (2), 输入端至下载 In端的光强传递函数 D 可以得到: kr2rkr2b(τ1τ2τ3) 2 expi(φ1+φ2+φ3) 1 − t2rrτ2exp2iφ2 + trrtrb(τ2exp2iφ2 − 1)(τ1exp2iφ1 + τ3exp2iφ3 ) + t2rbτ1τ3exp2i(φ1+φ3). Schematic diagram of serially coupled dumbbell microring resonator. 利用哑铃型微环下载端反射峰进行波长编码 时, 需要反射谱具有良好的箱型滤波特性, 且具有 单一反射峰, 即不存在分裂峰 [13]. 针对半径分别为 40 μm-30 μm-40 μm 串联哑铃型微环, 利用方程 (1) 得到当反射谱不存在分裂峰时 , 耦 合 系 数 krb 与 krr 的对应变化曲线, 如图 2 所示. 当 krb 与 krr 的取值在斜线区域内 (即阴影部分区域), 反射 谱不存在分裂峰, 满足编码的基本条件. 相反的, 当 krb 与 krr 的取值在空白区域时, 反射谱会出现 分裂峰, 此时不符合编码条件 利用哑铃型微环下载端反射峰进行波长编码 时, 需要反射谱具有良好的箱型滤波特性, 且具有 单一反射峰, 即不存在分裂峰 [13]. 针对半径分别为 40 μm-30 μm-40 μm 串联哑铃型微环, 利用方程 (1) 得到当反射谱不存在分裂峰时 , 耦 合 系 数 krb 与 krr 的对应变化曲线, 如图 2 所示. 当 krb 与 krr 的取值在斜线区域内 (即阴影部分区域), 反射 谱不存在分裂峰, 满足编码的基本条件. 相反的, 当 krb 与 krr 的取值在空白区域时, 反射谱会出现 分裂峰, 此时不符合编码条件
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