把组成光纤光栅法布里-珀罗腔的两个光纤光栅的初相位纳入了讨论范围,用耦合波方程推导了任意初相位下光纤光栅法布里-珀罗腔的透射和反射率的表达式。其中的相位因子包含了由光传播常数调制的腔长、光纤光栅的相位突变、光纤光栅初相位和由光纤光栅空间频率调制的光栅长度等四部分。分析了光纤光栅初相、由光栅空间频率调制的光栅长度两个因子对反射谱的影响,并提出了一种把光纤光栅法布里-珀罗腔等效为理想法布里-珀罗腔的方法。 The initial phases of the two FBG composing the fiber grating Fabry-Perot cavity are included in the scope of the discussion, and the transmission and reflectivity of the FBG Fabry-Perot cavity under any initial phase are derived from the coupled wave equation formula. The phase factor contains four parts: cavity length modulated by light propagation constant, phase change of fiber grating, initial phase of fiber grating and grating length modulated by the spatial frequency of fiber grating. The influence of the two factors on the reflection spectra of the FBG initial phase, the grating length modulated by the spatial frequency of the grating is analyzed. A new method is proposed, in which the fiber grating Fabry-Perot cavity is equivalent to the ideal Fabry-Perot cavity Methods.