少模光纤模式差分群时延的设计与优化

Design and Optimization of Mode Differential GroupDelayfor Few-Mode Fiber

基于少模光纤(FMF)的模分复用(MDM)传输系统,模式差分群时延(MDGD)是影响系统设计的关键因素之一。考虑实际光纤制备工艺,数值分析了阶跃折射率(SI)光纤、渐变折射率(GI)光纤、带有外下陷包层的阶跃型光纤和带有外下陷包层的渐变型光纤中不同的MDGD特性。在支持四个导模条件下,优化设计得到两种不同折射率剖面分布的四模光纤,分别具有较大的MDGD(LP11,LP12,LP02与LP01的MDGD分别是4.65,10.02,11.73ps/m)和较小的MDGD(LP11,LP12,LP02与LP01的MDGD分别是-0.049,-0.258,-0.168ps/m)。制备了阶跃折射率分布的少模光纤,其实测基模的损耗为0.23dB/km(1550nm)和0.37dB/km(1310nm)测量及分析结果证明其能够支持MDM应用。

In mode division multiplexing （MDM） transmission system using few-mode fiber （FMF）, mode differential group delay （MDGD） is one of the key factors that influence the system performance. Considering the practical fiber fabrication technique, the MDGD characteristics between different modes of step-index （SI） fiber, graded-index （GI） fiber, trench-assisted SI fiber, and trench-assisted GI fiber are numerically investigated. Under the condition of supporting four modes, two optimized refractive index profiles of FMFs with high and low MDGDs are presented. The high MDGDs of LPu, LP12, LP02 versus LP01 are 4.65, 10.02, 11.73 ps/m, respectively; while low MDGDs of LPM, LP12, LPo2 versus LP0 are - 0. 049, -0. 258, - 0. 168 ps/m, respectively. We fabricate and characterize the FMF with a SI profile, whose loss of fundamental mode is 0.23 dB/km at 1550 nm and 0.37 dB/km at 1310 nm. The measurement and analysis results indicate that it can be used for futuro MDM transmission system.