US4515474A
Expired / Lapsed
US
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Method and apparatus for determining peak temperature along an optical fiber
Assignee: United States Department of Energy
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Filing: 1982-07-29
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Granted: 1985-05-07
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Expires: 2002-07-29
Abstract
Abstract The invention relates to a new method and new apparatus for determining the hottest temperature or the coldest temperature prevailing along the length of an optical-fiber light guide. The invention is conducted with an optical fiber capable of supporting multidiode propagation of light and comprising a core, a cladding, and a jacket. The core is selected to have (1) a higher refractive index than the core and the cladding and (2) a relatively high negative temperature coefficient of refractive index. A light beam capable of establishing substantially single-mode propagation in the core is launched into an end thereof at an angle to the axis. The angle is increased to effect the onset of light refraction from the core into the cladding. The value of the launch angle corresponding to the onset is determined and then used to establish the refractive index of the core corresponding to the onset angle. The maximum temperature prevailing along the fiber then is determined from the (1) refractive index so determined and (2) the temperature coefficient of refractive index for the core. The invention is based on the finding that the launch angle corresponding to the onset of refraction into the cladding is uniquely determined by the maximum value of the ratio of the core refractive index to the cladding refractive index, which maximum occurs at the hottest point along the fiber.
Inventors
- 👤 Richard J. Fox
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 16:03
CPC Classifications
G; G01; G01K; G01K11/00; G01K11/32
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
154 words
Temperature-sensing apparatus, comprising: an optical fiber capable of supporting multimodal propagation of light and including (a) a core whose refractive index decreases with increasing temperature, (b) a cladding therefor having a lower refractive index than said core, and (c) a jacket for said cladding having a lower refractive index than said cladding, a light source mounted to launch into said core a light beam defining with the core axis a launch angle of progressively changing magnitude, said light beam being selected to establish substantially single-mode light propagation in said core, light-responsive means associated with said cladding for generating a first output indicative of onset of light refraction therein from said core, means responsive to the first output for generating a second output indicative of the value of the launch angle coincident with said onset, and means responsive to the second output for generating an output indicative of the fiber temperature corresponding to said value.
Claim 2
Dependent Claim
154 words
Temperature-sensing apparatus, comprising: an optical fiber capable of supporting multimodal propagation of light and including (a) a core whose refractive index decreases with increasing temperature, (b) a cladding therefor having a lower refractive index than said core, and (c) a jacket for said cladding having a lower refractive index than said cladding, a light source mounted to launch into said core a light beam defining with the core axis a launch angle of progressively changing magnitude, said light beam being selected to establish substantially single-mode light propagation in said core, light-responsive means associated with said cladding for generating a first output indicative of onset of light refraction therein from said core, means responsive to the first output for generating a second output indicative of the value of the launch angle coincident with said onset, and means responsive to the second output for generating an output indicative of the fiber temperature corresponding to said value.
Claim 3
Dependent Claim
12 words
The apparatus of claim 1 wherein said core is an organic liquid.
Claim 4
Dependent Claim
10 words
The apparatus of claim 1 wherein said cladding is silica.
Claim 5
Dependent Claim
30 words
The apparatus of claim 1 wherein said light source comprises a gas laser whose output is directed into said core via a reflective surface which is movable about an axis.
Claim 6
Dependent Claim
17 words
The apparatus of claim 4 further including means for moving said reflective surface stepwise about said axis.
Claim 7
Independent Claim
161 words
A method for generating an output indicative of the maximum temperature prevailing in an optical-fiber, said method comprising: providing an optical fiber capable of supporting multimodal propagation of light and including (a) a core whose refractive index decreases with increasing temperature, (b) a cladding therefor having a lower refractive index than said core, and (c) a jacket for said cladding having a lower refractive index than said cladding, launching into said core a light beam defining a launch angle with the axis of said core, said beam being selected to establish substantially single-mode light propagation in said core, increasing said launch angle to effect onset of light refraction from said core into said cladding, determining the value of said launch angle coincident with said onset, determining from said value, the corresponding minimum refractive index for said core, and determining from said minimum refractive index and the temperature coefficient of refractive index of said core, the corresponding peak temperature for said fiber.
Claim 8
Independent Claim
161 words
A method for generating an output indicative of the maximum temperature prevailing in an optical-fiber, said method comprising: providing an optical fiber capable of supporting multimodal propagation of light and including (a) a core whose refractive index decreases with increasing temperature, (b) a cladding therefor having a lower refractive index than said core, and (c) a jacket for said cladding having a lower refractive index than said cladding, launching into said core a light beam defining a launch angle with the axis of said core, said beam being selected to establish substantially single-mode light propagation in said core, increasing said launch angle to effect onset of light refraction from said core into said cladding, determining the value of said launch angle coincident with said onset, determining from said value, the corresponding minimum refractive index for said core, and determining from said minimum refractive index and the temperature coefficient of refractive index of said core, the corresponding peak temperature for said fiber.
Claim 9
Dependent Claim
12 words
The method of claim 6 wherein said core is an organic liquid.
Claim 10
Dependent Claim
10 words
The method of claim 7 wherein said liquid is silicone.
Claim 11
Dependent Claim
15 words
The method of claim 6 wherein said light beam is generated by a gas laser.
Claim 12
Independent Claim
173 words
A method for generating an output indicative of the minimum temperature prevailing in an optical fiber, said method comprising: providing an optical fiber capable of supporting multimodal propagation of light and including (a) a core whose refractive index is essentially independent of temperature, (b) a cladding therefor having a refractive index which is lower than that of said core and which increases with decreasing temperature, and (c) a jacket for said cladding having a lower refractive index than said cladding, launching into said core a light beam defining a launch angle with the axis of said core, said beam being selected to establish substantially single-mode light propagation in said core, increasing said launch angle to effect onset of light refraction from said core into said cladding, determining the value of said launch angle coincident with said onset, determining from said value, the corresponding minimum refractive index for said core, and determining from said minimum refractive index and the temperature coefficient of refractive index of said cladding the corresponding minimum temperature for said fiber.
Claim 13
Independent Claim
173 words
A method for generating an output indicative of the minimum temperature prevailing in an optical fiber, said method comprising: providing an optical fiber capable of supporting multimodal propagation of light and including (a) a core whose refractive index is essentially independent of temperature, (b) a cladding therefor having a refractive index which is lower than that of said core and which increases with decreasing temperature, and (c) a jacket for said cladding having a lower refractive index than said cladding, launching into said core a light beam defining a launch angle with the axis of said core, said beam being selected to establish substantially single-mode light propagation in said core, increasing said launch angle to effect onset of light refraction from said core into said cladding, determining the value of said launch angle coincident with said onset, determining from said value, the corresponding minimum refractive index for said core, and determining from said minimum refractive index and the temperature coefficient of refractive index of said cladding the corresponding minimum temperature for said fiber.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-05-06 | 1988-11-05 | 1989-05-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-05-06 | 1992-11-05 | 1993-05-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-05-06 | 1996-11-05 | 1997-05-07 | $7700.00 | Window Closed / Lapsed |