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选用紫外固化型环氧树脂,采用光刻技术在FR-4基板上制备了平行排布的多模聚合物光波导。波导具有阶跃折射率分布,相邻波导间隔为250μm,可与并带后的50μm芯径多模光纤实现多通道低损耗耦合。通过搭建测试平台,对波导的插入损耗、串扰及错位容限进行了测量与分析。实验结果表明,所制备光波导的损耗小于0.05dB/cm,串扰小于-60dB。波导在错位容限方面性能良好,当输入端错位±5μm时,系统增加的插入损耗小于0.2dB。同时根据实际波导建立仿真模型,采用光束传播法分析了不同入射条件下的模式能量分布、差分模式延时及耦合效率。计算结果表明,使用与波导具有相近纤芯尺寸的入射光纤不仅可以减小耦合损耗和串扰,还能减少激发起的高阶模式数,提高波导的距离带宽积,优化光波导的综合传输性能。所制备的聚合物光波导作为组成光印刷电路板的核心光器件具有良好的应用前景。
UV curable epoxy resin was chosen to fabricate multimode polymeric optical waveguides parallel to the FR-4 substrate by photolithography. The waveguide has a step index profile with an adjacent waveguide spacing of 250 μm and enables multi-channel, low-loss coupling with the 50 μm-core multimode optical fiber after banding. By setting up a test platform, the waveguide insertion loss, crosstalk and misalignment tolerance were measured and analyzed. Experimental results show that the optical waveguide has a loss of less than 0.05 dB / cm and a crosstalk of less than -60 dB. The waveguide performs well with misalignment tolerances, with an insertion loss of less than 0.2 dB added to the system when the input misalignment is ± 5 μm. At the same time, a simulation model was established based on the actual waveguide, and the beam energy distribution, differential mode delay and coupling efficiency under different incident conditions were analyzed by using the beam propagation method. The calculated results show that the use of an incident fiber with a similar core size to the waveguide can reduce the coupling loss and crosstalk, reduce the number of high-order modes excited, increase the distance-bandwidth product of the waveguide, and optimize the overall transmission performance of the optical waveguide. The prepared polymer optical waveguide has good application prospect as the core optical device of the optical printed circuit board.