Patent US4243320A successfully refreshed from Google Patents.
US4243320A
Expired / Lapsed
US
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Methods for testing optical fibres
Assignee: Corning Research and Development Corp
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Filing: 1979-03-20
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Granted: 1981-01-06
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Expires: 1999-03-20
Abstract
Abstract The invention uses the phenomenon of self-coupling by which light emitted from, and reflected back into, a laser produces self-coupling with consequent change in lasing activity. The invention proposes using the laser as a detector by inducing the self-coupling and monitoring the change in lasing activity. The invention enables fibre length, and the position of a reflective discontinuity in a fibre to be determined without the sophisticated and costly equipment required by current optical time domain reflectometry techniques.
Inventors
- 👤 Kevin S. Gordon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 05:25
CPC Classifications
G; G01; G01M; G01M11/00; G01M11/30; G01M11/31; G01M11/3109; G01B; G01B11/00; G01B11/02; H; H04; H04B; H04B10/00; H04B10/07; H04B10/071; H01; H01S; H01S5/00; H01S5/0014; H01S5/0028; H01S5/06; H01S5/065
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
189 words
A method for determining the position of a reflective discontinuity in an optical fibre comprising the steps: applying the output of an electrical pulse generator to a semiconductor laser to generate a train of recurrent light pulses; directing the train of recurrent light pulses into one end of the fibre; monitoring the level of lasing activity in the laser; varying the pulse repetition frequency of the electrical pulse generator until a frequency obtains at which light pulses self couple into the laser after reflection from the reflectivity discontinuity, the laser then undergoing a marked change in the level of changing activity owing to interference of the reflected light with light being generated within the laser; successfully halving the pulse repetition frequency obtained; after each frequency reduction, monitoring the level of lasing activity to determine the lowest frequency, F, at which said change in lasing activity exists; and thereby determining the distance of the reflective discontinuity from the formula 2L=vT where T is the period at frequency F; v is the speed of light in the fibre; and L is the distance between the fibre end and the reflective discontinuity.
Claim 2
Independent Claim
189 words
A method for determining the position of a reflective discontinuity in an optical fibre comprising the steps: applying the output of an electrical pulse generator to a semiconductor laser to generate a train of recurrent light pulses; directing the train of recurrent light pulses into one end of the fibre; monitoring the level of lasing activity in the laser; varying the pulse repetition frequency of the electrical pulse generator until a frequency obtains at which light pulses self couple into the laser after reflection from the reflectivity discontinuity, the laser then undergoing a marked change in the level of changing activity owing to interference of the reflected light with light being generated within the laser; successfully halving the pulse repetition frequency obtained; after each frequency reduction, monitoring the level of lasing activity to determine the lowest frequency, F, at which said change in lasing activity exists; and thereby determining the distance of the reflective discontinuity from the formula 2L=vT where T is the period at frequency F; v is the speed of light in the fibre; and L is the distance between the fibre end and the reflective discontinuity.
Claim 3
Dependent Claim
35 words
A method as claimed in claim 1 in which the level of lasing activity is monitored by monitoring the peak lasing pulse output, such peak output being a function of the level of lasing activity.
Claim 4
Dependent Claim
35 words
A method as claimed in claim 1, in which the level of lasing activity is monitored by monitoring power drawn by the laser, the power drawn being a function of the level of lasing activity.
References Cited (Backward Citations)
US4012149A
Cited
US4070118A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-01-06 | 1984-07-07 | 1985-01-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-01-06 | 1988-07-07 | 1989-01-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-01-06 | 1992-07-07 | 1993-01-06 | $7700.00 | Window Closed / Lapsed |