Huang Quandong, Wang Xibin, Dong Jiangli, Zheng Zhaoqiang, Xu Ou, Fu Songnian, Peng Di, Li Jianping, Qin Yuwen
Opt Express. 2022 Apr 11;30(8):12751-12759. doi: 10.1364/OE.454537.
We report an ultra-broadband LP mode converter with high purity based on integrated two shunt-wound long-period fiber gratings (LPFGs) and an adiabatic Y-junction, together with a high-order-mode bandpass filter. Two shunt-wound LPFGs are inscribed by CO laser in a two-mode fiber to achieve a 10 dB bandwidth of 50 nm and 51 nm at resonance wavelengths of 1530 nm and 1570 nm, respectively. Meanwhile, the Y-junction fabricated by lithography can be operated over S + C+L band to combine the converted LP mode. The presented ultra-broadband mode converter is able to achieve a mode conversion efficiency of 95%, together with a wavelength-dependent loss of less than 3 dB over the S + C+L band. This device has low modal crosstalk of 17 dB between the LP and LP modes, because most of the residual LP mode is further filtered by a high-order-mode bandpass filter at the output port of the Y-junction. The insertion loss of mode converter is estimated to be lower than 2.7 dB, due to the use of low loss polymer material during the fabrication. The proposed ultra-broadband LP mode converter with high purity is promising for the application of ultra-broadband mode-division-multiplexing transmission systems.
我们报道了一种基于集成两个并联长周期光纤光栅（LPFG）和一个绝热Y型结以及一个高阶模带通滤波器的高纯度超宽带LP模式转换器。通过CO激光在双模光纤中写入两个并联长周期光纤光栅，在1530nm和1570nm的共振波长处分别实现了50nm和51nm的10dB带宽。同时，通过光刻制造的Y型结可在S+C+L波段工作，以合并转换后的LP模式。所提出的超宽带模式转换器能够实现95%的模式转换效率，并且在S+C+L波段上波长相关损耗小于3dB。该器件在LP和LP模式之间具有17dB的低模式串扰，这是因为大部分残余LP模式在Y型结的输出端口被高阶模带通滤波器进一步滤除。由于在制造过程中使用了低损耗聚合物材料，模式转换器的插入损耗估计低于2.7dB。所提出的具有高纯度的超宽带LP模式转换器在超宽带模式分割复用传输系统的应用中具有广阔前景。
