用于全光再生的磁控光振荡结构研究

【作者】 卢鑫；

【导师】 武保剑；

【作者基本信息】 电子科技大学 ， 光学工程， 2011， 硕士

【摘要】 在长距离大容量的光通信中,人们为了克服电子瓶颈,采用全光信息处理技术,其中包括全光3R再生(再定时、再整形和再放大)。目前各种光振荡结构已广泛用于全光时钟提取。磁光光纤光栅(MFBG)将传统光栅结构和磁光效应复合在一起,可通过磁光效应来改变导波光的传输特性,在智能时钟提取方面具有潜在应用。本文研究了磁控光振荡结构的传输特性,主要研究工作如下:1.根据磁光微扰理论,推导了磁光相位光栅的耦合模方程和相应的转移矩阵。分析了折射率初始相位和磁光效应对磁光相位光栅传输特性的影响,给出了高反射率光栅的反射系数公式,以便于分析磁光光栅组成的光振荡结构。2.研究了由MFBG构成的法布里-珀罗(FP)振荡结构(MFBG-FP),采用多光束干涉法和转移矩阵法分析了MFBG-FP的透射特性。在高反射率的条件下,给出了透射峰间隔、磁光效应和折射率初始相位差引起的透射峰移动的表达式。研究表明,MFBG-FP的透射峰间隔随光栅折射率调制深度的增大而增大,随光栅有效折射率和光栅长度的增大而减小;MFBG的折射率初始相位差和磁光效应可使MFBG-FP结构的透射谱发生平移。实际中,可采用磁光效应补偿初始相位差引起的谱线移动;并且当FP结构内磁光晶体的磁光耦合系数大于MFBG的时,MFBG-FP结构的磁可调性增强。3.软件仿真结果表明,MFBG-FP结构透射峰的不均匀特性使得该结构不利于时钟提取。但可将其设计为单通道的窄带滤波器。4.在上述理论指导下,为了实现可调的时钟提取,研究了磁控光纤参量振荡器(MC-FOPO)。采用多光束干涉法,得到了圆、线偏振光入射时,MC-FOPO的输出光场。研究表明,泵浦光功率须在恰当的范围内才能得到质量较好的时钟信号;使用磁控可调延时方案可以满足环长与传输速率之间微米量级的的匹配精度要求,磁控精度可达10pm/Gs。更多还原

【Abstract】 To avoid electronic bottleneck in the long optical communication system, all-optical information processing has been applied, such as 3R regeneration (retiming, reshaping and reamplifying). So far many kinds of optical oscillators have been applied to extract clock. Magneto-optic fiber Bragg grating (MFBG) is a kind of periodic waveguide with magneto-optic (MO) effect. The transmission characteristics of guided wave can be changed by MO effect so that it has large potential in intelligent clock extraction. The transmission characteristics of magnetically controllable (MC) optical oscillators are analyzed in this thesis. The research works are as follows:1. Based on MO perturbation theory, the coupled mode equation and its corresponding transfer matrix of phase modified MFBG are provided. The influence of the initial phase of effective refractive index distribution of gratings and MO effect on the performance of phase modified MFBG is investigated. The phase of reflective coefficient of high reflection gratings is proposed to facilitate the analysis of MFBG constructed optical oscillator.2. The transmission characteristics of the MFBG-based Fabry-Perot (MFBG-FP) oscillator cavity is analyzed by multi-beam interference theory and transfer matrix approach. The expression of transmission peaks interval, shifted length of transmission peaks induced by MO effect and initial phase of effective refractive index are provided in the case of high reflection of MFBG. Analysis shows that the interval of transmission peaks changes proportionally with refractive index perturbation and conversely with effective refractive index and length of gratings; the transmission peaks can be shifted due to MO effect and initial phase of effective refractive index. In practice, the MO effect can compensate the influence of initial phase of effective refractive index on transmission peaks; the magnetic tunability of MFBG-FP structure can be further enhanced if the magneto-optic coefficient of MO crystal in the FP cavity is larger than MFBG’s.3. The result of software simulation shows that MFBG-FP is not suitable for clock extraction because of the non-uniform interval of transmission peaks. But it can be designed as a single channel narrow band filter.4. According to the analysis above, the MC fiber optic parameter oscillator (FOPO) is investigated to realize the clock extraction. The output optical field of MC-FOPO is provided by multi-beam interference theory. Analysis shows that the jitter of extracted clock is low on the condition that the pump optical power is in a proper range; the proposal of magnetically controllable time delay can fulfill the matching accuracy (micron scale) of loop length and data speed, whose tunable accuracy is up to 10pm/Gs.更多还原