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OPTICAL FIBER SENSING
 FBG Method

A proposal for advanced optical fiber sensing!

Large measuring points,
a wide measuring range and quick phenomena!

  Compared with the conventional FBG method,
Measuring points: A maximum of 100 points
can be installed per line.
Measuring range: Can be expanded up to ± 5000 µst.
Quick phenomenon : Copes with a sampling speed of 500 Hz.

TDM Method
(Time Division Multiplexing)
WDM Method
(Wavelength Division Multiplexing)


The FBG sensing system is not affected by electromagnetic noise. In addition to the essentially anti-explosive feature of optical fibers, with no fear of lightning damage, features include (1) small elements (2) suitable sensitivity and (3) the possibility of arranging multiple sensors on one piece of fiber. However, with conventional systems (fig. on the right), since identification by sensor is dependent upon FBG wavelengths, the measuring range of the sensors and the number of sensors on one line are in a trade-off relation and about eight observation points per line is about the limit for securing a practical measuring range.
This is because the suitable wavelength range that can be used is limited.
Under the new measuring system (fig. on the left), a system is adopted by which identifying the sensor is made by the time in which the FBG light returns, and thus, FBG of 100 observation points can be arranged on one piece of fiber.
Also, the detection of wavelength can be speeded up by use of semiconductors, and a sampling speed of 500 Hz has been realized.



   The following applications are possible

Baserock collapse monitoring --- Lightning resistance, use of multiple sensors on one line, eg. displacement meters, piezometer, rain gauge, etc.
Landslide monitoring --- Lightning resistance, use of multiple sensors on one line, eg. water level sensor, displacement meter, rain gauge, etc.
Oil and gas storage base --- Explosion proof, use of multiple sensors on one line, eg. water level sensor, inclinometer, displacement meter, etc.
In relation to the Shinkansen --- Electromagnetic noise resistance, withstands high voltage, use of dynamic measuring, displacement meter, accelerometer etc.

 


Various sensors using the FBG method
(scheduled to be placed on the market soon)

FBG water level sensor

FBG sensor for water level measurement.
Calculation of water level is made possible by accurately measuring water pressure by relative pressure to atmospheric pressure.

Feature:
  Although of 1FGB structure, its temperature characteristics are good, with a waterproof and pressure resistant structure.

Applications:
  Measuring underground water levels
  Measuring the water levels of dams and water tanks
FBG displacement meter
This is a sensor for measuring large displacement.

Feature:
  Although of 1FBG structure, its temperature characteristics are good, with superior long-term stability, waterproofing and rigidity. Stable data measurement is possible even outdoors.

Applications:
  Measuring precursory phenomenon of landslides, etc.
  Measuring displacement of ground
  Measuring displacement of bridges, etc.
FBG temperature meter


Measures temperature with high accuracy.

Feature:
  The casing is made to be highly resistant to environmental conditions (water resistance, pressure resistance), and stable measuring over extended periods is possible.

Applications:
  Measuring the temperature of concrete, outdoors and underground
The shape and specifications are subject to change without notice or obligation.

Other sensors are being developed.

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