Distributed sensor and method using coherence multiplexing of fiber-optic interferometric sensors

US4699513A · kind A · utility

Assignee

• Stanford University · US

Inventors

• Janet L. Brooks · Mountain View, US
• Moshe Tur · Nes Ziona, IL
• Robert C. Youngquist · Cocoa, US
• Byoung Y. Kim · Menlo Park, US
• Robert H. Wentworth · Matawan, US
• Herbert J. Shaw · Stanford, US
• Kjell Blotekjaer · Trondheim, NO

Key dates

• Filing date: May 28, 1985
• Grant date: Oct 13, 1987
• Expiry date: May 28, 2005

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04J14/002
• WIPO field: Optics
• WIPO sector: Instruments

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 interferometers connected in series configuration by a common optical fiber, which provides multiplexed output signals from the sensors to another plurality of interferometers comprising receivers. Functional equivalents of the series configuration provide sensors and receivers co…