Patent ID: 8681322
Filing Date: 2014-03-25
Classification: E21B,G01L,G01S

Abstract:
1. A method for estimating a distance to a position along an optical fiber, the method comprising: generating an optical signal via a measurement unit, the optical signal having a wavelength that is within a wavelength range, the optical signal modulated via a modulation signal having a modulation frequency; transmitting the modulated optical signal from a light source into the optical fiber, the optical fiber in contact with a moveable strain inducing element located at the position along the optical fiber, the optical fiber including a plurality of sensing locations configured to reflect light within the wavelength range when under strain from the strain inducing element and transmit light within the wavelength range when not under strain from the strain inducing element; receiving a reflected signal including light reflected from at least one of the sensing locations; demodulating the reflected signal with a reference signal to generate reflected signal data, and transforming the reflected signal data from a frequency domain into a spatial domain to provide a measurement set corresponding to a length of the optical fiber; and determining the distance to the position along the optical fiber based on the reflected signal data, wherein determining the distance includes identifying a peak in the transformed reflected signal data.