Biomedical Engineering Reference
In-Depth Information
Mirrored
fiber ends
Laser
3 dB
Detector
Coupler
(a)
D
Laser
Signal
processor
D
(b)
Laser
Detector
(c)
Detector
Laser
(d)
Partially transmitting mirrors
FIGURE 4.5
(a) Michelson, (b) Mach-Zehnder, (c) SAGNAC, and (d) Fabry-Perot interferometers.
design considerations applicable to the entire class of sensors. The fiber mag-
netometer is implemented as an all-fiber Mach-Zehnder interferometer in
which one branch has been made sensitive to magnetic fields by coupling to
a magnetostrictive material. The Mach-Zehnder magnetometer is capable of
sensing very small axial strains in the sensing fiber.
An early potential application of the fiber magnetometer was a sensor in
mine applications. This utilized the improved sensitivity over flux gate mag-
netometers in proper detection of perturbations of the local magnetic field
due to a moving vehicle containing large amounts of ferromagnetic mate-
rial. Potential applications of the fiber magnetometer include [6] tank, truck,
aircraft, and ship detection; electric current monitor; geophysical magnetic
disturbance monitor; magnetic compass; metal detector; VLF receiver; light-
ning monitor; traffic controller; and multi-influence target detector.
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