The internal deformation in clay core wall rockfill dam is a primary parameter to evaluate the structure health of this dam type.However,the inner deformation monitoring has always been a challenge since it can not be detected by traditional equipment accurately.This paper presents a kind of fiber Bragg grating(FBG) strain sensor based on the principle of friction and end-bearing piles,which is characterized by its small size,ease of connection serially,high strain sensitivity,etc.The novel dist..