单光纤光栅实现窄带全光纤反射器的分析

提出了一种由单个光纤光栅和一个光纤方向耦合器组成的新型全光纤反射器,推导出了当光栅为均匀 Bragg 光栅、器件任意端口输入时,任何一端口的输出解析式。分析表明器件具有法布里-珀罗腔干涉仪的特点,耦合器的耦合比系数类似于法布里-珀罗腔的反射率, 耦合比系数越大,输出光谱半高全宽度(FWHM)越窄, 消光比越好。当耦合比系数大于 0.8 时,FWHM 可以窄到0.02nm,消光比大于 0.9。如果光栅是“强”耦合,器件具有均匀分布的多通道梳状输出特性;光栅为“弱”耦合时,则能实现 FWHM 小于 0.02nm 的单频输出。器件只需单个光栅,克服了制作两个完全相同光栅的困难。

Analysis on all-fiber narrow bandwidth reflector using single fiber Bragg grating

A novel all-fiber reflector composed of single Bragg grating and a fiber directional coupler is proposed. For the case of uniform fiber Bragg grating with input from an grating arm, an analytical formulation of the output at any arm has been derived. The analysis shows that the reflection spectrum is the multiple beams interference, and the coupling ratio is similar to the reflection coefficient of Fabry-Perot cavity. The larger the ratio is, the finer the extinction ratio(Er) is and the narrower the full-width at half maximum (FWHM) will be. When the ratio is greater than 0.8, the FWHM can be narrowed down to 0.02nm and the extinction ratio will be more than 0.9. If grating is "strongly" coupled, the device features multi-channel comb output with uniform distribution. When grating is "weakly" coupled, then single frequency output with a FWHM less than 0.02nm can be obtained. The device only needs one single grating so the difficulties in making two entirely identical gratings disappear.