Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1985-02-08
1987-10-06
Willis, Davis L.
Optics: measuring and testing
By particle light scattering
With photocell detection
250227, 356349, 356351, G01B 902
Patent
active
046979263
ABSTRACT:
A distributed sensor system including an optical source having a short coherence length for optionally continuously monitoring each sensor in the system. In one preferred embodiment, an array of fiber-optic sensors are organized in a ladder configuration, with the sensors positioned in spaced relation and defining the rungs of the ladder. Light transmitted through the sensors is multiplexed onto a return arm of the ladder, with sensor spacing being such that interference between light from different sensors is prevented. The multiplexed signals are received by an optical fiber receiver which couples the multiplexed light with an interfering optical reference signal to produce a phase difference signal representing conditions influencing selected sensors. Embodiments are disclosed for use of either pulsed or continuous wave light sources. In another preferred embodiment, the sensors comprise a plurality of Mach-Zehnder interferometers connected in series configuration by a common optical fiber, which provides multiplexed output signals from the sensors to a plurality of Mach-Zehnder interferometers comprising receivers. The optical path length differences between the arms of each of the sensors are selected to prevent interference between the multiplexed sensor output signals from various sensors. The optical path lengths through the sensors and receivers are structured so that each receiver produces a phase difference signal relating to conditions affecting light transmission through a specific sensor. A phase and amplitude modulation technique is disclosed for providing heterodyned output signals from the distributed sensor system.
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Brooks Janet L.
Cutler Cassius C.
Fesler Kenneth A.
Shaw Herbert J.
Youngquist Robert C.
Koren Matthew W.
The Board of Trustees of the Leland Stanford Junior University
Willis Davis L.
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