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US 4,399,565 AGranted
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
AssigneeLignes Telegraphiques et Telephoniques
InventorsBertrand Jarret, Rose Cordier
Life of this patent
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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.
Claims7
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.
4 more elements
Dependencies are inferred from the claim text.