基于双包层光纤和长周期光纤光栅的带通滤波器

A bandpass filter based on double-clad fiber and long-period fiber grating

为了获得制作简易、成本低廉的光学带通滤波,研究了一种由双包层光纤和机械致长周期光纤光栅(MLPFG)构成的全光纤带通滤波器.理论分析了双包层光纤环半径与能量耦合(从纤芯到内包层)的关系,运用耦合模理论计算得到了不同压力下MLPFG的传输光谱图.实验通过缠绕得到光纤环并利用弹簧对光纤施加压力得到MLPFG,在光纤环直径12 mm和缠绕匝数15匝以及光纤长40 mm且受力60 N时,在中心波长1 546 nm附近实现了带通滤波,其通带带宽为4.15 nm,旁瓣抑制比为16.1 d B.这一无源光纤器件可广泛应用于多波长激光器和光纤传感等.

In order to obtain a simple,low cost optical bandpass filtering,an all-fiber bandpass filter composed of double-clad fiber and mechanical-induced long-period fiber grating（ MLPFG） is studied.Firstly,the relationship between radius of double-clad fiber coil and coupling power（ from core to inner cladding） is studied. Then the transmission spectrum of MLPFG at different pressure can be figured using coupled-mode theory. In the experiment,the optical fiber ring is obtained by winding and the pressure is applied to the optical fiber by the spring to obtain MLPFG. Finally,the bandpass filtering is achieved at wrapping fiber ring 12 mm diameter,winding turns 15 turns,fiber length 40 mm and force 60 N near the center wavelength of 1 546 nm. The passband bandwidth is 4. 15 nm and the side-lobe suppression ratio is16. 1 d B. This passive optical device can be widely used in multi-wavelength lasers and optical fiber sensing.