Michael Jason Todd

US Patent:

6674928, Jan 6, 2004

Filed:

Jul 31, 2001

Appl. No.:

09/917643

Inventors:

Gregg A. Johnson - Fairfax VA
Michael D. Todd - Alexandria VA
Bryan L. Althouse - Davidsonville MD
Chia-Chen Chang - Rockville MD

Assignee:

The United States of America as represented by the Secretary of the Navy - Washington DC

International Classification:

G02B 600

US Classification:

385 12, 385 13, 385 14, 385 37

Abstract:

A new optical sensing device containing fiber Bragg gratings, a scanning bandpass filter, an interferometer and multiple photodetectors is disclosed. The present invention also describes a new system and method for fibre Bragg grating (FBG) sensor interrogation and multiplexing. The new system combines a scanning Fabry-Perot (SFP) bandpass filter used to wavelength-multiplex multiple gratings in a single fiber, and an unbalanced Mach-Zehnder fibre interferometer made with a 3Ã3 coupler to detect strain-induced wavelength shifts. A passive technique for interferometer drift compensation using non-sensing FBGs is included in the system. A complete prototype system interrogates four gratings in a single fiber at a Nyquist sampling rate up to 10 kHz, with a noise floor measured near 4 n Hz above 0. 1 Hz. The inclusion of the interferometer drift compensation technique is shown to make quasi-static measurements feasible.

US Patent:

6957576, Oct 25, 2005

Filed:

Jul 11, 2003

Appl. No.:

10/618328

Inventors:

Neal G. Skinner - Lewisville TX, US
John R. Dennis - Bozeman MT, US
Michel Leblanc - Plano TX, US
Gregg Johnson - Fairfax VA, US
Michael D. Todd - Alexandria VA, US

Assignee:

Halliburton Energy Services, Inc. - Houston TX

International Classification:

E21B047/06

US Classification:

7315251, 73716

Abstract:

A well pressure and temperature measurement system and method are provided. In a described embodiment, a sensor system includes multiple strain sensors attached to a structure which changes dimensionally in response to well pressure and temperature changes. The strain sensors may be fiber optic sensors. The structure may be tubular and the strain sensors may detect axial and hoop strains in the structure.