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理论分析了基于光纤光栅的全光纤多腔Fabry-Perot(FP)结构透射谱特性,推出包含任意多个腔时的传输矩阵函数通用公式以及对称两腔结构的能量传输率具体计算公式,给出在光栅阻带内中心波长处产生单谐振传输峰需满足的条件,并通过数值计算进行了验证。在此基础上比较分析了单腔与两腔FP结构下,中心波长1550 nm处产生谐振透射峰的光谱特性,结果表明引入两腔结构后谐振峰的平坦性及其过渡带滚降特性都得到了改善。详细计算并模拟了腔长及光纤光栅特性变化对两腔FP结构透射谐振峰谱型造成的影响,总结出滤波器设计原则,并得出结论:增大光纤光栅反射率能够优化谐振峰滚降特性,通过适当选取腔长及光栅反射率大小,此结构能够用于窄带单通道选择或多通道波长的解复用。
The transmission spectrum characteristics of all-fiber multi-cavity Fabry-Perot (FP) structure based on fiber gratings are theoretically analyzed. The general formulas of transfer matrix function including any number of cavities and the specific energy transfer formula of symmetrical two-cavity structure are given. The condition that the single resonance transmission peak must be generated at the central wavelength of the grating stop band is validated by numerical calculation. On this basis, the spectral characteristics of resonance transmission peak at 1550 nm at single center and two-chamber FP are analyzed. The results show that both the flatness of the resonance peak and the roll-off of the transition band are obtained Improved. The influences of cavity length and the characteristics of FBG on the transmission resonance peak shape of two-cavity FP structure are calculated and simulated in detail. The principle of the filter design is summarized and the conclusion is drawn that increasing the FBG reflectivity can optimize the resonance peak roll-off The structure can be used for single-channel narrowband selection or multi-channel wavelength demultiplexing by proper selection of cavity length and grating reflectance.