Patent ID: 11860028
Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 4:
5. A signal processing device comprising:
receiver for receiving in-phase components and quadrature components of scattered light generated by a light pulse that has entered a measurement target optical fiber, and acquiring reference vectors and measurement vectors, the reference vectors constituted by, among the in-phase components and the quadrature components of the scattered light, in-phase components and quadrature components at both ends of a given target segment of the measurement target optical fiber in a reference state, and the measurement vectors constituted by in-phase components and quadrature components at both ends of the target segment of the measurement target optical fiber at a given time; and
detector for determining that physical vibration has been applied to the target segment of the measurement target optical fiber when a triangular shape formed by a vector on a near end side and a vector on a far end side of the target segment of the measurement target optical fiber is envisioned for each of the reference vectors and the measurement vectors and shape change in a triangular shape formed by the measurement vectors with respect to a triangular shape formed by the reference vectors is a predetermined value or more;
wherein, on the near end side and the far end side of the target segment of the measurement target optical fiber, the detector calculates a difference between a vector obtained by rotating the measurement vector using a rotation matrix and the reference vector, and uses the minimum value of the difference obtained when rotation using the rotation matrix is changed as the shape change.