Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1997-03-11
1999-02-02
Le, Que T.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
25022719, 356345, H01J 516
Patent
active
058668985
ABSTRACT:
The present invention significantly improves the signal to noise ratio (SNR) in a passive optical array by adding erbium-doped optical amplifiers between the sensor couplings to offset the coupler splitting losses. Optical amplifiers are inserted between the sensor couplings along the signal path, and the gain of the amplifiers is designed to offset losses due to the previous coupling. The overall SNR can be maintained without significant degradation even for large numbers of sensors. In a first aspect of the present invention, the amplifiers are located along the distribution and return buses directly after the couplers, except possibly for the last sensor. In a second aspect of the present invention, the amplifiers are located directly before the couplers. The optical amplifiers preferably are made of short lengths of erbium-doped fiber spliced into the distribution and return buses. Improvements can be made to the SNR when the distribution bus coupling ratios are set at optimal values. The value of the optimal coupling ratio depends upon the amplifier configuration, the excess loss and other configuration parameters. In alternative embodiments, sensors are grouped into parallel configurations along the distribution and return buses to increase the number of sensors without a corresponding increase in the number of amplifiers and with an improvement in system performance to a certain point.
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Digonnet Michel J.F.
Hodgson Craig W.
Shaw H. John
Wagener Jefferson L.
Le Que T.
The Board of Trustees of the Leland Stanford Junior University
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