根据光纤光栅周期的长短不同，可将周期性的光纤光栅分为短周期（Λ<1μm）和长周期（Λ>1μm）两类。- According to the optical fiber grating period length is different, the fiber Bragg grating period is divided into short period (<1 μ m) and long period (>1 μ m) tw

This function approximates the long period the peak of the scattering curve on the frame range ‘start’ to ‘finish’. Note: not valid for noisy data. -This function approximates the long period the peak of the scattering curve on the frame range