Vibration detection device and vibration detection method
A vibration detection apparatus is presented which can avoid occurrence of a point where detection sensitivity deteriorates in vibration detection of a scattered light intensity monitor according to optical frequency multiplexing. A multi-dimensional space having as many dimensions as the number of frequencies to be used, causes scattered light intensity change at each optical frequency to correspond to each axis, plots a scattered light signal as a vector on the space, performs linear approximation passing through an origin on the space having a plurality of plotted vector points as original data, and performs vibration detection using a direction vector of an approximate straight line obtained as a result of the approximation.
1 . A vibration detection apparatus using a time-domain reflection measurement method, comprising:
an optical tester that makes optical frequency multiplex pulses including a plurality of fundamental optical frequencies incident on an optical fiber and acquires a Rayleigh backscattered light intensity; and
a control arithmetic unit that executes causing the optical tester to perform preliminary measurement in which the fundamental optical frequencies are changed by a moving optical frequency for each of the optical frequency multiplex pulses and are incident on the optical fiber to acquire a Rayleigh backscattered light intensity,
detecting direction vectors having temporal changes in the Rayleigh backscattered light intensity with respect to the fundamental optical frequencies as elements for each point of the optical fiber on the basis of the Rayleigh backscattered light intensity acquired through the preliminary measurement, and statistically processing the direction vectors for each moving optical frequency to create an approximate direction vector, and
causing the optical tester to perform main measurement in which the optical frequency multiplex pulses of the plurality of fundamental optical frequencies are incident on the optical fiber, direction vectors having temporal changes in the Rayleigh backscattered light intensity with respect to the fundamental optical frequencies as elements are detected for each point of the optical fiber, and vibration is detected from inner products of the direction vectors and the approximate direction vector.
2 . A vibration detection method using a time-domain reflection measurement method, comprising:
performing preliminary measurement in which a plurality of fundamental optical frequencies included in optical frequency multiplex pulses are changed by a moving optical frequency for each of the optical frequency multiplex pulses and are incident on an optical fiber to acquire a Rayleigh backscattered light intensity;
detecting direction vectors having temporal changes in the Rayleigh backscattered light intensity with respect to the fundamental optical frequencies as elements for each point of the optical fiber on the basis of the Rayleigh backscattered light intensity acquired through the preliminary measurement, and statistically processing the direction vectors for each moving optical frequency to create an approximate direction vector; and
performing main measurement in which the optical frequency multiplex pulses of the plurality of fundamental optical frequencies are incident on the optical fiber, direction vectors having temporal changes in the Rayleigh backscattered light intensity with respect to the fundamental optical frequencies as elements are detected for each point of the optical fiber, and vibration is detected from inner products of the direction vectors and the approximate direction vector.