公开(公告)号：US20210255005A1

公开(公告)日：2021-08-19

申请号：US17275327

申请日：2019-09-12

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Tatsuya Okamoto ,  Daisuke Iida ,  Hiroyuki Oshida ,  Tetsuya Manabe

IPC: G01D5/353 ,  G01H9/00 ,  E02D29/14

Abstract: A manhole position identification method of the present invention includes: measuring, from an end of an optical fiber, a temporal variation in scattering light from the optical fiber when an impact blow is applied to a cover of a manhole located on a path of the optical fiber, so as to obtain temporal variations in a scattering light intensity distribution in a longitudinal direction of the optical fiber; determining an occurrence of vibration due to the impact blow based on the temporal variations at positions in the scattering light intensity distribution, so as to identify an impact blow position on the optical fiber; and associating the impact blow position on the optical fiber with a map position of the manhole whose cover has received the impact blow, so as to identify a position of the manhole expressed in terms of optical fiber length from the end.

公开(公告)号：US20210018343A1

公开(公告)日：2021-01-21

申请号：US17042638

申请日：2019-03-26

Applicant: Nippon Telegraph and Telephone Corporation

Inventor： Hiroshi Takahashi ,  Kunihiro Toge ,  Tomokazu Oda ,  Tetsuya Manabe

IPC: G01D5/353

Abstract: An environmental property measurement apparatus includes a unit configured to receive probe light in a desired mode from one end of a measurement optical fiber, a unit configured to receive, from the other end of the measurement optical fiber, a light pulse in the desired mode as a pump light pulse with respect to the probe light, the light pulse having a frequency difference corresponding to a Brillouin frequency shift of the measurement optical fiber relative to the probe light on a high frequency side, and a unit configured to receive second probe light having the frequency difference corresponding to the Brillouin frequency shift of the measurement optical fiber relative to the probe light on a low frequency side from the other end of the measurement optical fiber, the second probe light being probe light with respect to the probe light in another mode different from the desired mode.