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Multi-Sensor up to 100 & Quasi-Dynamic Monitoring up to 2 kHz
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Long-Term and Wide Range Health Monitoring with Innovative Fibre Optics
Sensing
Providing long-term reliability and cost effectiveness
in infrastructure measurements
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Outline of the system
Health monitoring for civil-structures such as roads, railroads, sewers, and electric
power stations, can provide crucial information not only when building such
structures but for the drawing up of a long-term renewal plan. Optical fibre
sensing has a number of advantages over conventional electrical strain
gauges: it is immune to electromagnetic fields; exhibits the ability
to take many measurement points along a single fibre - greatly improving
the ease at which sensors can be multiplexed; has excellent long-term accuracy; and can be embedded
within or bonded to structures without the risk of de-bonding during operation,
to name but a few. So far several different optical sensing techniques have
found their way onto the market place. Among these we are introducing fibre
optical sensing with Fibre Bragg Grating (FBG) incorporated with both innovative
FBG writing technology and the Fibre Sensor Interrogator (FSI).
Tobishima's fibre optics monitoring system is being introduced into Japan
for the first time with up to 100 multiplexed sensors in a single cable
(1600 with 16 cables), maximal 9 km long monitoring, and high reliability
& long-term durability even at low cost. These advantages of Tobishima's
fibre optics monitoring system resulted from several unique techniques
of FBGs and FSI, provided by our collaborator, Insensys Ltd, the leading company of fibre optics sensing. Combing the innovative
optical sensing techniques of Insensys Ltd with Tobishima's NDT and Civil
Technology, this epoch-making system has now become commercially available.
 Strain measuring process using FBG sensors
| 1. |
Bragg gratings are written into an optical fibre using two intersecting
ultraviolet laser beams. |
| 2. |
When light emitted from the FSI reaches an FBG through an optical fibre, the light is reflected back down the fibre to the FSI unit. |
| 3. |
When an FBG is subjected to a change in strain (or temperature) the reflected
wavelength from it changes. |
| 4. |
The strain can be measured from the shift of wavelength. |
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Relationship between strain and shift in the wavelength |
Principle of measuring strain by FBG sensor |
FSI unit
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Two-axis displacement sensor
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Key Characteristics
The following are the key characteristics of Tobishima's fibre optics infrastructure
monitoring.
- Not influenced by ambient electromagnetic noise around the measuring points
(long-term reliability)
- Stabilized long term monitoring for a semi-permanent period except for
physical damage of FBG sensors
- Up to 16 channels available providing up to 1600 sensors
- Quasi-dynamics monitoring up to 2 kHz in one sensor
- Reduces space between FBG sensors to 1.3 m
- Maximum monitoring length up to 9,000 m
- A cost effective, accurate, reliable, compact and light FSI
Applications
- Health monitoring of long structures, e.g., tunnels, bridges, seawalls,
etc
- Slope stability monitoring
- Structural health and condition monitoring of wind energy for wind power
energy plants
- Structural health and condition monitoring of buildings
More information can be available. Please contact us.
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