Fiber-optic seismic sensor
First Claim
Patent Images
1. A vibration sensor including:
- a first optical fiber having;
an input end;
an output end; and
a coil portion therebetween of a first predetermined optical path length when said sensor is not subject to vibration to be sensed;
a second optical fiber having;
an input end;
an output end; and
a coil portion therebetween of a second predetermined optical path length when said sensor is not subject to vibration to be sensed;
a closed body adapted to be coupled to the vibration to be sensed to vibrate said body, said coil portions of said first and second optical fibers being positioned within said body; and
means to vary said optical path length of at least said first optical fiber coil portion with the vibration of said body including;
a mass having;
a first side; and
a second opposite side, said first and second sides being orientated generally at right angles to the vibration to be sensed; and
elastic means to fill said body and encapsulate said coil portions of said first and second optical fibers and said mass within said body, said mass being positioned between said coil portion of said first optical fiber and said coil portion of said second optical fiber, whereby movement of said mass within said body caused by vibration of said body causes said elastic means to exert differential pressures between said coil portions of said first and second optical fibers.
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Abstract
A vibration sensor is constructed by providing two preferably matched coils of fiber-optic material. When the sensor experiences vibration, a differential pressure is exerted on the two fiber coils. The differential pressure results in a variation in the relative optical path lengths between the two fibers so that light beams transmitted through the two fibers are differently delayed, the phase difference therebetween being a detectable indication of the vibration applied to the sensor.
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Citations
17 Claims
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1. A vibration sensor including:
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a first optical fiber having; an input end; an output end; and a coil portion therebetween of a first predetermined optical path length when said sensor is not subject to vibration to be sensed; a second optical fiber having; an input end; an output end; and a coil portion therebetween of a second predetermined optical path length when said sensor is not subject to vibration to be sensed; a closed body adapted to be coupled to the vibration to be sensed to vibrate said body, said coil portions of said first and second optical fibers being positioned within said body; and means to vary said optical path length of at least said first optical fiber coil portion with the vibration of said body including; a mass having; a first side; and a second opposite side, said first and second sides being orientated generally at right angles to the vibration to be sensed; and elastic means to fill said body and encapsulate said coil portions of said first and second optical fibers and said mass within said body, said mass being positioned between said coil portion of said first optical fiber and said coil portion of said second optical fiber, whereby movement of said mass within said body caused by vibration of said body causes said elastic means to exert differential pressures between said coil portions of said first and second optical fibers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A vibration sensor including:
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a first optical fiber having; an input end; an output end; and a coil portion therebetween of a first predetermined optical path length when said sensor is not subject to vibration to be sensed; a second optical fiber having; an input end; an output end; and a coil portion therebetween of a second predetermined optical path length when said sensor is not subject to vibration to be sensed; a body adapted to be coupled to the vibration to be sensed to vibrate said body, said coil portions of said first and second optical fibers being positioned within said body, said body including; first and second, generally parallel, facing inner surfaces; and means to vary said optical path length of at least said first optical fiber coil portion with the vibration of said body including; a generally cylindrical elastic mandril having; first and second end surfaces; a cylindrical surface positioned therebetween, said first and second end surfaces being positioned adjacent said first and second inner surfaces of said body to couple the vibration to be sensed into said mandril, said first and second optical fiber coil portions being wrapped about said mandril cylindrical surface, said mandril cylindrical surface including; a first cylindrical portion positioned adjacent said first end surface; and a second cylindrical portion positioned adjacent said second end surface; and means to couple said first optical fiber coil portion to expansion and contraction of said cylindrical surface, said first optical fiber coil portion including; a first coil part; and a second coil part, said first coil part of said first optical fiber coil portion being tightly wrapped to said first cylindrical portion to couple said first optical fiber coil portion to expansion and contraction of said cylindrical surface, said second optical fiber coil portion including; a first coil part; and a second coil part, said second coil part of said second optical fiber coil portion being tightly wrapped to said second cylindrical portion to couple said second optical fiber coil portion to expansion and contraction of said cylindrical surface. - View Dependent Claims (10)
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11. A vibration sensor including:
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a first optical fiber having; an input end; an output end; and a coil portion therebetween of a first predetermined optical path length when said sensor is not subject to vibration to be sensed; a second optical fiber having; an input end; an output end; and a coil portion therebetween of a second predetermined optical path length when said sensor is not subject to vibration to be sensed; a body adapted to be coupled to the vibration to be sensed to vibrate said body, said coil portions of said first and second optical fibers being positioned within said body, said body including; first and second, generally parallel, facing inner surfaces; and means to vary said optical path length of at least said first optical fiber coil portion with the vibration of said body including; a generally cylindrical elastic mandril having; first and second end surfaces; a cylindrical surface positioned therebetween including; a first cylindrical portion positioned adjacent said first end surface; and a second cylindrical portion positioned adjacent said second end surface, said first and second end surfaces being positioned adjacent said first and second inner surfaces of said body to couple the vibration to be sensed into said mandril, said first and second optical fiber coil portions being wrapped about said mandril cylindrical surface; and means to couple said first optical fiber coil portion to expansion and contraction of said cylindrical surface, said first optical fiber coil portion including; a first coil part; and a second coil part, said first coil part of said first optical fiber coil portion being wrapped about and physically coupled to said first cylindrical portion to couple said first optical fiber coil portion to expansion and contraction of said cylindrical surface, and said second optical fiber coil portion including; a first coil part; and a second coil part, said second coil part of said second optical fiber coil portion being wrapped about and physically coupled to said second cylindrical portion to couple said second optical fiber coil portion to expansion and contraction of said cylindrical surface. - View Dependent Claims (12, 13, 14)
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15. A vibration sensor including:
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a first optical fiber having; an input end; an output end; and a coil portion therebetween of a first predetermined optical path length when said sensor is not subject to vibration to be sensed; a second optical fiber having; an input end; an output end; and a coil portion therebetween of a second predetermined optical path length when said sensor is not subject to vibration to be sensed; a body adapted to be coupled to the vibration to be sensed to vibrate said body, said coil portions of said first and second optical fibers being positioned within said body, said body including; first and second, generally parallel, facing inner surfaces; and means to vary said optical path length of at least said first optical fiber coil portion with the vibration of said body including; a generally cylindrical elastic mandril having; first and second end surfaces; a cylindrical surface positioned therebetween including; a first cylindrical portion positioned adjacent said first end surface; and a second cylindrical portion positioned adjacent said second end surface, said first and second end surfaces being positioned adjacent said first and second inner surfaces of said body to couple the vibration to be sensed into said mandril, said first and second optical fiber coil portions being wrapped about said mandril cylindrical surface, and means to couple said first optical fiber coil portion to expansion and contraction of said cylindrical surface including; said first optical fiber coil portion being wrapped about and physically coupled to said first cylindrical portion to couple said first optical fiber coil portion to expansion and contraction of said cylindrical surface and being physically isolated from said second cylindrical portion; and said second optical fiber coil portion being wrapped about and physically coupled to said second cylindrical portion to couple said second optical fiber coil portion to expansion and contraction of said cylindrical surface and being physically isolated from said first cylindrical portion. - View Dependent Claims (16, 17)
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Specification