Extrinsic fiber optic displacement sensors and displacement sensing systems

Patent · Fri Dec 31 23:00:00 EST 1993

OSTI ID:869229

Murphy, Kent A ^[1]; Gunther, Michael F ^[2]; Vengsarkar, Ashish M ^[3]; Claus, Richard O ^[4]

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1. Roanoke, VA
2. Blacksburg, VA
3. Scotch Plains, NJ
4. Christiansburg, VA

An extrinsic Fizeau fiber optic sensor comprises a single-mode fiber, used as an input/output fiber, and a multimode fiber, used purely as a reflector, to form an air gap within a silica tube that acts as a Fizeau cavity. The Fresnel reflection from the glass/air interface at the front of the air gap (reference reflection) and the reflection from the air/glass interface at the far end of the air gap (sensing reflection) interfere in the input/output fiber. The two fibers are allowed to move in the silica tube, and changes in the air gap length cause changes in the phase difference between the reference reflection and the sensing reflection. This phase difference is observed as changes in intensity of the light monitored at the output arm of a fused biconical tapered coupler. The extrinsic Fizeau fiber optic sensor behaves identically whether it is surface mounted or embedded, which is unique to the extrinsic sensor in contrast to intrinsic Fabry-Perot sensors. The sensor may be modified to provide a quadrature phase shift extrinsic Fizeau fiber optic sensor for the detection of both the amplitude and the relative polarity of dynamically varying strain. The quadrature light signals may be generated by either mechanical or optical means. A plurality of the extrinsic sensors may connected in cascade and multiplexed to allow monitoring by a single analyzer.

• Research Organization: Virginia Polytech Inst/St Univ
• DOE Contract Number: AC21-89MC25159
• Assignee: Center For Innovative Technology (Herndon, VA)
• Patent Number(s): US 5301001
• OSTI ID: 869229
• Country of Publication: United States
• Language: English

Related Subjects

/356/250/
air
air gap
air interface
allow
allowed
amplitude
analyzer
arm
behaves
biconical
cascade
cavity
changes
comprises
conical taper
connected
contrast
coupler
detection
difference
displacement
displacement sensor
dynamically
embedded
extrinsic
fabry-perot
fiber
fiber optic
fibers
fizeau
form
fresnel
front
fused
gap
generated
glass
identically
input
intensity
interface
interfere
intrinsic
length
light
light signal
light signals
means
mechanical
mode fiber
modified
monitored
monitoring
mounted
move
multimode
multimode fiber
multiplexed
observed
optic
optic displacement
optic sensor
optical
optical means
output
phase
phase difference
phase shift
plurality
polarity
provide
purely
quadrature
quadrature phase
reference
reflection
reflector
relative
sensing
sensor
sensor comprises
sensors
shift
sic fiber
signals
silica
single
single-mode
single-mode fiber
strain
surface
surface mount
surface mounted
systems
tapered
tube
unique
varying