Instrumentation Service
Deformation Monitoring with Fiber Optic Sensors (SOFO V)
Keywords: SOFO, fiber optic sensor, health monitoring, displacement,
strain, Michelson interferometer
 Setup
of SOFO V |
SOFO (a French acronym for Surveillance d'Ouvrages par Fibres
Optiques) is a deformation measurement system based on low-coherence interferometry
using an fiber optic sensor.
The sensor consists of a pair of single-mode fibers installed in the structure
to be monitored. One of the fibers, called the measurement fiber, is housed in
a pipe, attached at the two ends of the measurement zone and pre-tensioned in
between. The other fiber, called the reference fiber, is placed loose in the
same pipe. All deformation of the structure changes the difference in length
between the two fibers.
To make an absolute measurement of this path imbalance, a low-coherence double
Michelson interferometer is used. The first channel consists of the measurement
and reference fibers, while the second is contained in the portable reading unit. |
Features
- Excellent long-term stability
- Long-gage fiber optic deformation sensor
- High resolution: 0.002 mm
- Easy and quick to install and measure
|
- Embeddable in concrete
- Automatic and remote operation
- Insensitive to temperature, EM fields, corrosion
|
System specifications
Reading unit (SOFO V)
- Resolution: 0.002 mm (independent of gage length)
- Precision: Better than 0.2% of the measured deformation
- Size: 470 x 390 x 175 mm（Weight: 13 kg）
- Operating temperature: -20°C~60°C
- Max. number of channels: Unlimited
- Data logger capacity: Max. 80,000 measurements
- Automatic measurement: Interval can be set with a PC
- Remote measurement: By PHS，cellular phone, fixed line
|
SOFO sensor
- Gage length: 0.2~50 m（Diameter: 8 mm
- Dynamic range: Elongation: 1.0%
Contraction:
0.5%
- Operating temperature: -50°C~110°C
- Watertight: 6 bar
- Calibration: Not necessary
- Temperature sensitivity: 0.5 μm/°C
- Insensitive to temperature, EM fields, corrosion
|
Applications
 |
 |
 |
Deformation measurement
of a concrete bridge deck |
Deformation measurement of a containment vessel |
Embedded in concrete |
Experience: SOFO systems have been used in over 120 projects
all over the world (as of 2004).
