To provide a device capable of detecting a low-frequency vibration such as an earthquake by using a frequency change of light.
A circulation part formed on an optical fiber is mounted on an elastic body 2. Coherent light is allowed to enter the optical fiber in this state. When a low-frequency vibration is generated, the elastic body 2 is rocked, and the circulation part of the optical fiber is deformed. Displacement speed or displacement in the circulation part can be detected by detecting a frequency change as light, of light passing the circulation part. The elastic body 2 may be constituted of the first elastic member 21 and the second elastic member 22. In this case, the circulation part is mounted on each elastic member 21, 22, and thereby measurement accuracy of the low-frequency vibration can be improved.
KIKUYAMA SEIJI
AOKI TOMOYUKI
TANI TAKUYA
NAKADA FUMIO
SUZUKI KEIICHI
NOGUCHI SHIZUO
UJIGEN MASAYUKI
FUJII MAKI
TAISEI CORP
KAWASAKI GEOL ENGINEERING CO L
NITTOC CONSTRUCTION