US4853534A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical fiber sensing system
Assignee: GEC AEROSPACE Ltd
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Filing: 1988-03-11
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Granted: 1989-08-01
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Expires: 2008-03-11
Abstract
Abstract An optical fibre sensing system for monitoring and/or measuring temperatures or pressures distributed around an optical fibre sensing loop. Light source and coupler are provided for applying continuous wave light to the loop so that the light propagates simultaneously in opposite directions around the loop with the resultant light output from the loop being detected by a detector. Light pulse generating source and coupler cause light pulses to propagate in one direction only around the loop and by so doing produce transient variations in the propagation constant along the looped fibre in dependence upon the distributed temperature or pressure around the loop. The detector detects the phase changes occurring in the continuous wave light received from the sensing loop due to variations in temperature or pressure around the loop.
Inventors
- 👤 John P. Dakin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 04:56
CPC Classifications
G; G01; G01L; G01L1/00; G01L1/24; G01L1/242; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/353; G01D5/35383; G01K; G01K11/00; G01K11/32
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
149 words
An optical fibre sensing system for monitoring and/or measuring temperatures or pressures distributed over a predetermined path, in which the pre-determined path comprises an optical fibre defining a sensing loop, in which means are provided for applying continuous wave light to the sensing loop so that the light propagates simultaneously in opposite directions around said loop with the resultant light output from the loop being detected by detector means, in which pulse generating means is provided for generating short light pulses which propagate in one direction only around the sensing loop and by so doing produce transient variations in the propogation constant along the looped optical fibre in dependence upon the distributed temperature or pressure around the loop and in which the detector means detects the phase changes occurring in the continuous wave light received from the sensing loop due to variations in temperature or pressure around the loop.
Claim 2
Dependent Claim
149 words
An optical fibre sensing system for monitoring and/or measuring temperatures or pressures distributed over a predetermined path, in which the pre-determined path comprises an optical fibre defining a sensing loop, in which means are provided for applying continuous wave light to the sensing loop so that the light propagates simultaneously in opposite directions around said loop with the resultant light output from the loop being detected by detector means, in which pulse generating means is provided for generating short light pulses which propagate in one direction only around the sensing loop and by so doing produce transient variations in the propogation constant along the looped optical fibre in dependence upon the distributed temperature or pressure around the loop and in which the detector means detects the phase changes occurring in the continuous wave light received from the sensing loop due to variations in temperature or pressure around the loop.
Claim 3
Dependent Claim
41 words
An optical fibre sensing system as claimed in claim 1, in which the continuous wave light is fed into the sensing loop and the light output from the sensing loop is fed to the detector means through an optical directional coupler.
Claim 4
Dependent Claim
32 words
An optical fibre sensing system as claimed in claim 1, in which the light pulses generated by the pulse generating means are fed into the sensing loop through an optical directional coupler.
Claim 5
Dependent Claim
29 words
An optical fibre sensing system as claimed in claim 1, in which the short pulses generated by the pulse generating means are filtered out before reaching the detector means.
Claim 6
Dependent Claim
34 words
An optical fibre sensing system as claimed in claim 1, in which the wavelength of the short pulses generated by the pulse generating means is outside the wavelength response range of the detector means.
Claim 7
Dependent Claim
22 words
An optical fibre sensing system as claimed in claim 1, in which a polarisation--maintaining optical fibre is utilised for the optical fibre.
Claim 8
Dependent Claim
25 words
An optical fibre sensing system as claimed in claim 1, in which the sensing loop includes biasing means to provide maximum response to the pulses.
References Cited (Backward Citations)
US4634852A
Cited
US4767210A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-07-31 | 1993-01-30 | 1993-08-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-07-31 | 1997-01-30 | 1997-08-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-07-31 | 2001-01-30 | 2001-08-01 | $7700.00 | Window Closed / Lapsed |