Nec Corporation

Eitaro Misumi

Yutaka Yano

Masaki Nakano

Makoto Ogawa

Kenichi Nomura

Makoto Saitoh

Jun Muramatsu

A water pressure fluctuation measuring system detects a water pressure fluctuation. A cable, which includes an optical fiber, is provided on or in the ground of the seabed in such a way that the optical fiber is expanded and contracted according to the water pressure fluctuation. An optical output unit outputs monitoring light to the optical fiber. A partial reflection unit is provided on a path of the optical fiber in the cable and partially reflects the monitoring light. An optical reception unit receives reflection light reflected by the partial reflection unit. A calculation unit measures a length of the optical fiber to the partial reflection unit, based on a round-trip propagation time of the received reflection light, and monitors a change of the length over time.

Water pressure fluctuation measuring system and water pressure fluctuation measuring method

In order to facilitate fixed-point monitoring over a wide area and for a long time, this water area monitoring device comprises: a detection unit for information, such as water area intrusion, which detects, from sound data that is acquired by means of optical fibers installed in the water or the water bottom and is data pertaining to a sound or a vibration at the respective positions of the optical fibers, at least any one among sounds of water area intrusion or the like that indicate intrusion into a target water area or water area intrusion or the like, which is a prescribed behavior in the target water area, at a time at which sound data is acquired, and changes in sounds or vibrations not caused by the water area intrusion or the like; and an output unit which outputs information indicating the sound such as water area intrusion.

Water area monitoring device, water area monitoring system, water area monitoring method, and recording medium

An optical fiber cable () according to each of the present disclosures includes a long tube () and at least one optical fiber () held and passed through an inside of the tube (). The tube () expands and contracts in a longitudinal direction when water pressure on an outside of the tube () changes. When the tube () expands and contracts in the longitudinal direction, the expansion and contraction of the tube () in the longitudinal direction is transmitted to the optical fiber () to expand and contract the optical fiber () in the longitudinal direction.

Optical fiber cable and water pressure sensing system, and sensitivity correction method

A measurement system, a measurement device, and a measurement method being able to measure a flow speed for each position of an optical fiber are provided. According to one example embodiment, a measurement system includes: an object provided in a fluid, and generating a self-excited vibration by the fluid; an optical fiber provided in the fluid, and detecting the vibration; a light source outputting light P to the optical fiber; an acquisition unit acquiring backscattered light generated from the light P in the optical fiber and including a pattern indicating the vibration in a vibration position on the optical fiber to which the vibration of the fluid is transmitted; and a measurement unit measuring, from a pattern included in the backscattered light and indicating the vibration, a flow speed of the fluid in the vibration position.

Measurement system, measurement device, and measurement method to detect a direction in which fluid flows

A slight movement of the ground is detected. A cable, which includes an optical fiber, is provided to have friction with the ground in such a way that the optical fiber is expanded and contracted in accordance with the movement of the ground. An optical output unit outputs a monitoring light to the optical fiber. A partial reflection unit is provided on a path of the optical fiber in the cable and partially reflects the monitoring light. An optical reception unit receives a reflection light reflected by the partial reflection unit. A calculation unit measures the length of the optical fiber to the partial reflection unit based on a round-trip propagation time of the reflection light that has been received and monitors its changes over time.

Surveying system and surveying method

An optical fiber cable for sound wave sensing that uses a straight optical fiber and is capable of suppressing directivity is provided. The optical fiber cable for sound wave sensing includes a cover part () that is capable of covering a straight cable core () and is provided with a sound wave refraction part () which refracts sound waves made incident roughly perpendicularly to a longitudinal direction of the cable core () and makes the sound waves be incident diagonally to the longitudinal direction of the cable core (). The cover part () includes a gap filling part () which covers the sound wave refraction part ().

Growing community of inventors

Tokyo, Japan

Eitaro Misumi