01-08-2012, 02:37 PM
Fiber Optic Sensor Technology
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Introduction
Current applications
Mechanical measurements: force,
pressure, strain/stress,
displacement, temperature,
acceleration, vibration, acoustics
Electrical and magnetic
measurements
Chemical and biological sensing
Fiber Optic Sensor Classifications
Sensing region: Intrinsic vs. Extrinsic
Intrinsic fiber optic sensor has a sensing region within the fiber
and light never goes out of the fiber.
In extrinsic sensors, light has to leave the fiber and reach the
sensing region outside and then comes back to the fiber.
Optical modulation mechanism
Intensity modulated
Phase modulated
Wavelength modulated
Polarization modulated
Intensity Modulated Fiber Optic Sensors
Properties of intensity based sensors
Versatile
Simple design and easy signal interpretation
Usually suffer from intensity fluctuations and low
sensitivity
Phase Modulated Fiber Optic Sensors
Phase Demodulation Techniques
Passive demodulation: without phase modulation
Active demodulation: with feedback control or/and phase
modulation
Homodyne: optical frequency in the two arms of the fiber optic
interferometer are the same
Heterodyne: optical frequency in the two arms of the fiber optic
interferometer are different
Passive homodyne, active homodyne, and heterodyne