基于高折射率液体填充的花瓣形微结构光纤可调滤模特性

提出一种新型的可调滤模光纤结构,利用纤芯模式与微结构包层形成的超模群之间的耦合实现选择性滤模,采用花瓣形包层结构使包层中传输的模式更容易产生高的泄漏损耗;提出以液体填充包层介质柱,使包层形成的超模群有效折射率区间可以通过环境温度来调节,从而达到可调选择性滤模目的.利用液体柱的LP11模所形成的超模群,有效增大了其工作带宽和温度调谐范围.数值模拟结果表明,采用长度仅为71.4 mm的滤模光纤,可以使特定的抑制模式损耗达到20 dB以上,而其他模式损耗均在1 dB以下.提出的光纤可以在少模光纤传输系统中作为滤模器使用,以降低模式转换器、复用器/解复用器以及光开关和光路由等的模式串扰.

Tunable mode-selective characteristics of a mode-filter petal-fiber with liquid rods

In this paper, a novel tunable mode-filter optical fiber consisting of a high-index core and petal-shaped cladding surrounded by a high-index outer ring is proposed. The cladding of the fiber is formed with periodically arranged liquid rods that support cladding modes with effective indexes. These cladding modes form a two-super-mode group. The mode-selection is realized by the coupling between the core mode and the super-mode group. With the petal-shaped cladding, cladding mode can be transmitted at high loss. With the liquid rods, the index-band of super-mode group can be adjusted by external temperature field, thereby achieving the purpose of tunable mode-selective. The super-mode group formed by the LP₁₁ mode of the liquid rods effectively increases its operating bandwidth and temperature tuning range. The numerical simulation results show that the mode-filter fiber with a length of only 71.4 mm can achieve a particular mode loss more than 20 dB, while other modes' losses are below 1 dB. This special fiber can be used as a mode-filter in the few-mode fiber transmission system to reduce mode crosstalk of converters, multiplexer/demultiplexer, optical switch and optical routing.