Methods for determining optical properties of optical waveguide fibers using an optical time domain reflectometer
AssigneeCorning Incorporated
InventorThomas A. Hanson
Life of this patent
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Abstract
Methods for determining optical properties of an optical waveguide fiber using an optical time domain reflectometer (OTDR) are provided. The methods involve the removal of noise from an OTDR trace (signal) by fitting the noise component of the signal and then subtracting the fitted noise from the original signal to produce a noise-reduced signal. Optical properties are more readily determined from the noise-reduced signal than from the original signal. In particular, the noise-reduced signal can be used to determine axial optical properties of long fibers, e.g., fibers having a length of 50 kilometers or more.
Claims22
A method for determining an optical property of an optical waveguide fiber comprising the steps of:
- (a) applying a pulse of light to the optical waveguide fiber by means of an optical time domain reflectometer (OTDR);
- (b) detecting the light reflected back to the OTDR from the fiber and generating a set of first values at a set of signal points corresponding to the detected reflected light, said signal points extending along the length of the fiber and said set of first values having noise which varies locally along the length of the fiber (the "locally varying first noise");
- (c) determining an average slope for the set of first values;
- (d) determining a local slope value for each of the signal points from the set of first values;
- (e) forming a set of second values for the set of signal points, each of said second values comprising the local slope value at the signal point minus the average slope, said second values having noise which varies locally along the length of the fiber (the "locally varying second noise"), said locally varying second noise being an autocorrelated form of the locally varying first noise;
- (f) forming a set of third values for the set of signal points by filtering the set of second values with a set of filters, said filters being a function of the locally varying second noise and serving to subtract noise from the set of second values;
- and
- (g) determining the optical property of the optical waveguide fiber from the set of third values.
A method for determining an optical property of an optical waveguide fiber comprising the steps
- (a) applying a pulse of light to the optical waveguide fiber by means of an optical time domain reflectometer (OTDR);
- (b) detecting the light reflected back to the OTDR from the fiber and generating a set of first values at a set of signal points corresponding to the detected reflected light, said signal points extending along the length of the fiber;
- (c) removing noise from the set of first values based on the local character of the noise to produce a set of noise-reduced values for the set of signal points;
- (d) determining the optical property of the optical waveguide fiber from the set of noise-reduced values.
Dependencies are inferred from the claim text.