Patent ID: 9551809
Date: 2017-01-24
CPC Classifications: E21B,G01D,G01L,G01M,G01V,G02B

Claim:
1. An apparatus for performing a measurement of a downhole property, the apparatus comprising: an optical fiber having a series of sections with each section comprising a first fiber Bragg grating having a first resonant wavelength and a second fiber Bragg grating having a second resonant wavelength, a difference between the second resonant wavelength and the first resonant wavelength being greater than a dynamic wavelength range of each of the first and second fiber Bragg gratings, wherein fiber Bragg gratings are interleaved such that adjacent fiber Bragg gratings have different resonant wavelengths; an optical interrogator in optical communication with the optical fiber and configured to: emit a frequency domain light signal into the optical fiber, the frequency domain light signal comprising a swept wavelength for a first time duration and a chirp comprising a modulation of amplitude with a varying of wavelength for a second time duration that is less than the first time duration; receive a frequency domain return light signal from the optical fiber due to the emitted frequency domain light signal, the frequency domain return light signal comprising a resonant wavelength shift of each fiber Bragg grating due to the downhole property and a corresponding location of each fiber Bragg grating; and transform the frequency domain return signal into a time domain in order to determine the resonant wavelength shift of each fiber Bragg grating and the corresponding location of each interrogated fiber Bragg grating; a processor configured to convert the resonant wavelength shift of each interrogated fiber Bragg grating into the downhole property measurement; and an output interface coupled to the processor and configured to transmit a signal comprising the downhole property measurement and a corresponding location of the downhole property measurement to a signal receiving device.