Optical sensor array having multiple rungs between distribution and return buses and having amplifiers in the buses to equalize return signals

US6084233A · kind A · utility

Assignee

• Board of Trustees of the Leland Stanford Junior University · US

Inventors

• Craig W. Hodgson · Thousand Oaks, US
• Jefferson L. Wagener · New Hope, US
• Michel J. F. Digonnet · Palo Alto, US
• H. John Shaw · Stanford, US

Key dates

• Filing date: Jul 10, 1997
• Grant date: Jul 4, 2000
• Expiry date: Jul 10, 2017

Classification

• Technology area (CPC G): Physics
• CPC primary: G01H9/004
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

The present invention significantly improves the signal to noise ratio (SNR) in a passive optical array comprising sensors located in rungs between a distribution bus and a return bus. Erbium-doped optical fiber amplifiers are included in the buses proximate to each rung coupling to offset the coupler splitting losses. The gains of the amplifiers are selected to offset losses due to the couplings. The overall SNR can be maintained without significant degradation even for large numbers of sensors. In one aspect of the present invention, the amplifiers are located along the distribution and return buses directly after the couplers, except for the last coupler. In a second aspect, the amplifiers are located directly before each coupler. 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 preferred embodiments, sensors are grouped into parallel configurations in the rungs…