Biomedical Engineering Reference
In-Depth Information
Signal
processor
Light
source
Detector
Transmitting
fiber
Transducing
material/device
Perturbing
field
FIGURE 4.1
Intensity sensor.
Fiber waveguide can also be used simply to transmit information from any
transducer, including electromechanical or electronic, to a detection or pro-
cessing point. These sensors are the more fundamental of the fiber sensors,
and use multimode commercially available components in their construction.
Perhaps of more significant interest in terms of performance that is superior
to electronic sensors are the interferometric or phase modulation sensors.
4.3 PhaseModulationSensors
In the phase sensor, the perturbing field to be detected modulates, via a
transducer, the phase of coherent light in the sensing arm of an interferom-
eter. Figure 4.2 illustrates the fiber interferometric, or phase sensor. A fre-
quency-stable laser light source is coupled to a single-mode optical fiber and
then split into two legs of the sensor system: a sensing leg and a reference
Signal
processor
Detector
Laser
Transmitting
fiber
Modulator
Beam
splitter
Reference fiber
Sensing fiber
Perturbing field
FIGURE 4.2
Phase sensor.
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