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US4399565A
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US
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Device for triggering an alarm system in the event of insufficiency of the transmission level, for the receiver module of an optical-fiber transmission system
Assignee: Lignes Telegraphiques et Telephoniques LTT SA
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Filing: 1981-02-09
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Granted: 1983-08-16
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Expires: 2001-02-09
Abstract
Abstract An alarm-triggering device for the receiver of an optical-fiber transmission system including in series a filter which has a passband located externally with respect to the band of frequencies employed for optical-fiber transmission and the input of which is connected to an avalanche photodiode, an amplifier, a rectifier, a voltage comparator circuit, and alarm-triggering circuit.
Inventors
- 👤 Bertrand Jarret
- 👤 Rose Cordier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 21:50
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/60; H04B10/66; H04B10/69; H04B10/691; H04B10/6911
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
152 words
A device for triggering an alarm system in the event of insufficiency of the transmission level for the receiver of a transmission system which utilizes an optical fiber, comprising: a photodetector having an automatic gain regulation and producing noise in the event of said insufficiency of transmission level; a filter connected to said photodetector for passing said noise, said filter having a passband which is external to the frequency band employed for optical fiber transmission; means for amplifying said noise present at the output of said filter; means for rectifying said noise present at the output of said amplifying means; a circuit for comparing the amplitude of said noise to a threshold amplitude value, said comparing circuit being connected to the output of said rectifying means; and alarm-triggering means connected to the output of said comparing circuit for producing an alarm signal when said noise amplitude is greater than said threshold value.
Claim 2
Independent Claim
152 words
A device for triggering an alarm system in the event of insufficiency of the transmission level for the receiver of a transmission system which utilizes an optical fiber, comprising: a photodetector having an automatic gain regulation and producing noise in the event of said insufficiency of transmission level; a filter connected to said photodetector for passing said noise, said filter having a passband which is external to the frequency band employed for optical fiber transmission; means for amplifying said noise present at the output of said filter; means for rectifying said noise present at the output of said amplifying means; a circuit for comparing the amplitude of said noise to a threshold amplitude value, said comparing circuit being connected to the output of said rectifying means; and alarm-triggering means connected to the output of said comparing circuit for producing an alarm signal when said noise amplitude is greater than said threshold value.
Claim 3
Dependent Claim
26 words
A device according to claim 1, wherein the input of said filter is connected to the output of an amplifier which is supplied by said photodetector.
Claim 4
Dependent Claim
24 words
A device according to claim 2, further including means for automatically regulating the gain of said photo detector in accordance with said alarm signal.
Claim 5
Dependent Claim
30 words
A device according to claim 1 or claim 2, wherein the mean frequency of said filter is lower than the bottom limit of the frequency band employed for optical-fiber transmission.
Claim 6
Dependent Claim
30 words
A device according to claim 1 or claim 2, wherein the mean frequency of said filter is higher than the top limit of the frequency band employed for optical-fiber transmission.
Claim 7
Dependent Claim
24 words
A device according to claim 1, wherein said amplifying means are constituted by a first low-noise amplifier and a second ampifier connected in series.
Claim 8
Dependent Claim
13 words
A device according to claim 1, wherein said photodetector is an avalanche photodiode.
References Cited (Backward Citations)
US4249264A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-08-15 | 1987-02-14 | 1987-08-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-08-15 | 1991-02-14 | 1991-08-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-08-15 | 1995-02-14 | 1995-08-16 | $7700.00 | Window Closed / Lapsed |