But the stitching errors of electron-beam written phase masks always occur between neighboring sections,which can impact the reflectivity fluctuation of chirped Fiber Bragg Gratings (FBGs).

The analytical expression for the reflection-maximum wavelengths of the uniform fiber-grating F-P cavity is derived and explained by introducing equivalent F-P cavity length from its work principle,the reflection peak gap and the resonance peak numbers of the main band width are also obtained.

Hence the difference between two reflective wavelengths can be used to measure the changes of the outer refractive index accurately?and to reduce the effect of strain during the measurement.

The wave character of complex media and field detection information was analyzed using a nonreflecting wave equation and a staggered grid finite difference approach to simulate wave propagation in complex media with a zero offset profile, which avoids multiple reflections among layers.