The applications of diffractive optical elements in optical fiber communication

本论文研究了衍射光学元件在光通信中的应用。具体如下：1．基于偶数型Dammann光栅的半周期位相反转特性，提出一种新型的动态光耦合技术。通过调节两块位相互补的Dammann位相板之间的相对移动，只需要半周期的较小位移便可实现动态的分束和合束功能，且装置具有体积小、损耗小、能耗低的优点，其核心部分位相板可通过大规模集成电路工艺批量生产。我们设计制造出1*8 Dommonn光栅，搭建了1*8动态光藕合器。装置由输入输出光纤、互补的Dammann位相板、透镜和位移器等组成，实验上对输出光点的均匀度进行了测量，对该方案的可行性进行了验证。我们还进一步讨论了在密集波分复用中使用带来的误差以及今后的改进方向，该动态光拙合器对未来的中大规模秘合阵列的发展有积极的推动作用。2．基于Talbot位相编码位相板设计出光束扫描器和动态光开关。根据Talbot阵列照明器的特性，利用两块互补的Talbot位相板，通过较小位移便可精确控制衍射光出射光点的位置，从而以较低的损耗实现大扫描角度和多点数的光束扫描器以及大输出端口数目的光开关。装置具有衍射效率高、性能稳定等优点。理论分析了扫描点数（输出端口数目）、衍射效率（插入损耗）和光栅特征参数之间的关系，给出光开关的实施例，对位相板的实际制造和扫描器、光开关的搭建有重要指导意义。随着二元光学技术的进展，我们方案的优势会更加明显。In this dissertation, the applications of diffractive optical elements in optical fiber communication are studied as follows: 1. A new kind of dynamic optical coupling technique is realized based on the even-numbered Dammann gratings, which have the characteristic of phase inversion every half a period. With a half-period relative shift between the two complementary phase plates, the structure can achieve the function of either a beam combiner or a splitter. This proposal has the advantages of small volume, low loss and low energy consumption. And the phase plates, which are the core component of the device, can be mass-produced by the microelectronic technology. We have designed and fabricated 1*8 Dammann gratings and set up the dynamic optical coupler system, which includes input and output fibers, lens and a shifter etc. The uniformity of the output light spots is detected experimentally. It has been proved that the proposal is practical and superior to other methods, especially in the case of coupling arrays with a large number of output channels. Furthermore, the performance of this device is analyzed when it is used in DWDM. And some improvements are put forward as well. This dynamic coupling technique based on diffractive elements will promote the development of the large scale coupling devices. 2. Based on the property of the Talbot illuminator array, new types of beam scanner and optical switch have been proposed by employing a pair of complementary Talbot encoded phase plates. The output light beam can be accurately controlled via small shift between the two plates. Thus the beam scanners with a large diffractive angle and a large number of scanning points, as well as dynamic switches with a large number of output channels, can be realized with low loss. Our construction has high diffractive efficiency and stable capability. The relationship among the number of scanning points (output channels), diffractive efficiency (insertion loss) and the characteristic parameter of the phase grating is analyzed. We also analyze the phase plates and describe a 1*8 dynamic switch of this kind at length in this dissertation. Our work demonstrates a new direction of the applications of the diffractive optical elements in optical fiber communications. And with the development of the binary-optical technology, our proposal will have more advantages