19-11-2012, 12:01 PM
Fiber Optic Sensors
[attachment=40120]
How they work
Fiber optic sensors measure properties of their environment.
They can measure anything which changes the way light travels through the fiber, or alters the light’s properties.
What can they measure?
Temperature
Pressure
Strain
Displacement
Acceleration
Flow rate
Vibration
Chemical concentrations
Electrical and Magnetic Fields
Rotation rate
Methods of Measurement
Amplitude- and Intensity-Based Sensors
Frequency- and Wavelength-Varying Sensors
Polarization and Phase-Modulating Fiber-Optic Sensing
Frequency- and Wavelength-Varying Sensors
Map changes in frequency or wavelength to parameter of interest.
Low alteration of signal outside of sensing area.
Wavelength measurement is very sensitive; not strongly affected by light loss in connections, or source intensity fluctuations.
Advantages of Fiber Sensors
Many sensing applications could use mechanical or electronic sensors, but fiber sensors have advantages for some applications.
Explosive environments- no electricity to start fires
(ie. pressure sensors in rocket fuel tanks).
Corrosive environments- silica fiber is chemically resistant, unlike copper.
Hot environments- many of these sensors work above 750 F. (400 C) The sensor can be cast into aluminum metal.
Remote sensing- signal detection/processing can be done miles from active part of fiber sensor.
Small size! 125um fiber same thickness as 36 AWG wire.
Summary
There are several characteristics of optical fibers that allow them to be used for sensors. These include micro bending, interferometric effects, refractive index change, polarization change, fiber length change, fiber diffraction grating effects, and the Sagnac effect (light traveling in opposite directions around a loop used to sense rotation).
[attachment=40120]
How they work
Fiber optic sensors measure properties of their environment.
They can measure anything which changes the way light travels through the fiber, or alters the light’s properties.
What can they measure?
Temperature
Pressure
Strain
Displacement
Acceleration
Flow rate
Vibration
Chemical concentrations
Electrical and Magnetic Fields
Rotation rate
Methods of Measurement
Amplitude- and Intensity-Based Sensors
Frequency- and Wavelength-Varying Sensors
Polarization and Phase-Modulating Fiber-Optic Sensing
Frequency- and Wavelength-Varying Sensors
Map changes in frequency or wavelength to parameter of interest.
Low alteration of signal outside of sensing area.
Wavelength measurement is very sensitive; not strongly affected by light loss in connections, or source intensity fluctuations.
Advantages of Fiber Sensors
Many sensing applications could use mechanical or electronic sensors, but fiber sensors have advantages for some applications.
Explosive environments- no electricity to start fires
(ie. pressure sensors in rocket fuel tanks).
Corrosive environments- silica fiber is chemically resistant, unlike copper.
Hot environments- many of these sensors work above 750 F. (400 C) The sensor can be cast into aluminum metal.
Remote sensing- signal detection/processing can be done miles from active part of fiber sensor.
Small size! 125um fiber same thickness as 36 AWG wire.
Summary
There are several characteristics of optical fibers that allow them to be used for sensors. These include micro bending, interferometric effects, refractive index change, polarization change, fiber length change, fiber diffraction grating effects, and the Sagnac effect (light traveling in opposite directions around a loop used to sense rotation).