Anomaly detection system and abnormality detection method

To provide a chemical plant, the abnormality detection system and abnormality detection method abnormality occurring in facilities such as refineries plants and thermal power plants can be detected at an early stage. A abnormality detection system includes an optical fiber 26, the back-scattered light detecting section 20, and a data processing unit 30. The backscattered light detector 20 is connected to one end and the other end of the optical fiber 26, to obtain a first intensity distribution of the backscattered light is incident light to the optical fiber 26 from the one end, the other end obtaining a second intensity distribution of the backscattered light is incident light to the optical fiber 26 from. The data processing unit 30 effects a value relative to the first intensity distribution obtained by applying a first FIR filter obtained in backward scattered light detection section 30, a second FIR filter for the second intensity distribution the product of the value obtained by, calculated for each position in the longitudinal direction of the optical fiber 26 determines the presence or absence of abnormality from the result. .FIELD 8