Method and apparatus for detecting and compensating for a kink in an optic fiber
First Claim
1. A method for detecting and compensating for a kink in an optical fiber having a distal sensor for monitoring at least one parameter in an environment, wherein the optical fiber conveys light signals of a first wavelength and light signals of a second wavelength to and from the distal sensor, and wherein a photodetector records signal and reference values for the light signals of the first wavelength and for the light signals of the second wavelength at consecutive data points, the method comprising the steps of:
- (a) at a current data point,(i) storing a current signal value and a current reference value for the light signal of the first wavelength;
(ii) storing a current signal value and a current reference value for the light signal of the second wavelength; and
(iii) calculating a current ratio as a function of the current signal value for the light signal of the first wavelength, the current signal value for the light signal of the second wavelength, the current reference value for the light signal of the first wavelength and the current reference value for the light signal of the second wavelength;
(b) at a next consecutive data point,(i) storing a next signal value and a next reference value for the light signal of the first wavelength;
(ii) storing a next signal value and a next reference value for the light signal of the second wavelength; and
(iii) calculating a next ratio as a function of the next signal value for the light signal of the first wavelength, the next signal value for the light signal of the second wavelength, the next reference value for the light signal of the first wavelength and the next reference value for the light signal of the second wavelength;
(c) repeating steps (a) and (b) until a kink is detected in the optical fiber by determining if a difference between the current signal value for the light signal of the second wavelength and the next signal value for the light signal of the second wavelength is greater than a predetermined limit;
(d) after the kink is detected in step (c) calculating a true measurement of the parameter that compensates for the kink at each data point affected by the kink.
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Accused Products
Abstract
A method and apparatus are provided for detecting and compensating for a kink in an optical fiber. A distal sensor (11) monitors a level of a parameter in an environment in which the distal sensor is immersed. The distal sensor is disposed at a tip of the optical fiber (17) and the optical fiber conveys green light signals and near infrared (NIR) light signals to and from the distal sensor. A photodetector (59'"'"') records the signal and reference values for the green light signals and the NIR light signals conveyed by the optical fiber at consecutive data points. A microcontroller (42) is electronically coupled to the photodetector and receives the signal and reference values for the green light signals and the NIR light signals. A kink in the optical fiber is detected when a change between NIR signal values recorded at a pair of consecutive data points recorded by the photodetector is greater than a predetermined threshold. After the kink is detected, a true level of the parameter in the environment is calculated that compensates for the kink. More specifically, a true green signal value is determined based on a linear relationship between green and NIR signal values recorded at the pair of consecutive data points. The true green signal value is then used to calculate the true level of the parameter. In an alternative embodiment of the present invention, a warning is issued when the kink is detected and monitoring of the level of the parameter is discontinued.
82 Citations
42 Claims
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1. A method for detecting and compensating for a kink in an optical fiber having a distal sensor for monitoring at least one parameter in an environment, wherein the optical fiber conveys light signals of a first wavelength and light signals of a second wavelength to and from the distal sensor, and wherein a photodetector records signal and reference values for the light signals of the first wavelength and for the light signals of the second wavelength at consecutive data points, the method comprising the steps of:
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(a) at a current data point, (i) storing a current signal value and a current reference value for the light signal of the first wavelength; (ii) storing a current signal value and a current reference value for the light signal of the second wavelength; and (iii) calculating a current ratio as a function of the current signal value for the light signal of the first wavelength, the current signal value for the light signal of the second wavelength, the current reference value for the light signal of the first wavelength and the current reference value for the light signal of the second wavelength; (b) at a next consecutive data point, (i) storing a next signal value and a next reference value for the light signal of the first wavelength; (ii) storing a next signal value and a next reference value for the light signal of the second wavelength; and (iii) calculating a next ratio as a function of the next signal value for the light signal of the first wavelength, the next signal value for the light signal of the second wavelength, the next reference value for the light signal of the first wavelength and the next reference value for the light signal of the second wavelength; (c) repeating steps (a) and (b) until a kink is detected in the optical fiber by determining if a difference between the current signal value for the light signal of the second wavelength and the next signal value for the light signal of the second wavelength is greater than a predetermined limit; (d) after the kink is detected in step (c) calculating a true measurement of the parameter that compensates for the kink at each data point affected by the kink. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An apparatus for detecting and compensating for a kink in an optical fiber, wherein the optical fiber conveys light signals of a first wavelength and light signals of a second wavelength, the apparatus comprising:
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(a) a distal sensor that monitors a level of a parameter in an environment in which the distal sensor is immersed, wherein the distal sensor is disposed at a tip of the optical fiber and the optical fiber conveys light signals of the first wavelength and light signals of the second wavelength to and from the distal sensor; (b) a photodetector that records reference values for the light signals of the first wavelength and for the light signals of the second wavelength conveyed to the distal sensor by the optical fiber at consecutive data points, and wherein the photodetector records signal values for the light signals of the first wavelength and for light signals of the second wavelength conveyed from the distal sensor at consecutive data points; (c) a processing unit electronically coupled to the photodetector to receive the signal and reference values for the light signals of the first wavelength and the signal and reference values for the light signals of the second wavelength, said processing unit including memory means for storing program instructions, which control the processing unit so that it comprises; (i) storing means for storing the signal and reference values for the light signals of the first wavelength and the signal and reference values for the light signals of the second wavelength recorded by the photodetector at consecutive data points; (ii) detecting means for detecting the kink in the optical fiber, wherein an effect of the kink is to change the signal values for the light signals of the first wavelength and the signal values for the light signals of the second wavelength, wherein the detecting means determines if a change between the signal values for light signals of the second wavelength recorded at a pair consecutive data points is greater than a predetermined threshold; and (iii) measuring means for measuring an accurate level of the parameter in the environment after the kink is detected, wherein the measuring means compensates for the effect of the kink. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
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23. A method for issuing a warning after detecting a kink in an optical fiber having a distal sensor for monitoring a level of a parameter in an environment, wherein the optical fiber conveys light signals of a first wavelength and light signals of a second wavelength to and from the distal sensor, wherein a photodetector records reference values for the light signals of the first wavelength and for the light signals of the second wavelength conveyed to the distal sensor at consecutive data points, and wherein the photodetector records signal values for the light signals of the first wavelength and for the light signals of the second wavelength conveyed from the distal sensor at consecutive data points, the method comprising the steps of:
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(a) updating a current window of data, the data comprising a current median signal value for the light signal of the second wavelength and a current median level of the parameter; (b) updating a previous window of data, the data comprising a previous median signal value for the light signal of the second wavelength and a previous median level of the parameter; (c) comparing the current window of data to the previous window of data until the kink is detected in the optical fiber by; (i) determining if a difference between the current median signal value for the light signal of the second wavelength and the previous median signal value of the light signal of the second wavelength is greater than a predefined signal value threshold; and (ii) determining if a difference between the current median level and the previous median level is greater than a predefined parameter threshold; and (d) issuing a warning that the kink has occurred after determining that the predefined parameter threshold has been exceeded step (c). - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31)
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32. A method for detecting and compensating for a kink in an optical fiber having a distal sensor for monitoring at least one parameter in an environment, wherein the optical fiber conveys light signals of a first wavelength and light signals of a second wavelength to and from the distal sensor, and wherein a photodetector records signal and reference values for the light signals of the first wavelength and for the light signals of the second wavelength at consecutive data points, the method comprising the steps of:
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(a) at a current data point, (i) storing a current signal value and a current reference value for the light signal of the first wavelength; (ii) storing a current signal value and a current reference value for the light signal of the second wavelength; and (iii) calculating a current ratio as a function of the current signal value for the light signal of the first wavelength, the current signal value for the light signal of the second wavelength, the current reference value for the light signal of the first wavelength and the current reference value for the light signal of the second wavelength; (b) at a next consecutive data point, (i) storing a next signal value and a next reference value for the light signal of the first wavelength; (ii) storing a next signal value and a next reference value for the light signal of the second wavelength; and (iii) calculating a next ratio as a function of the next signal value for the light signal of the first wavelength, the next signal value for the light signal of the second wavelength, the next reference value for the light signal of the first wavelength and the next reference value for the light signal of the second wavelength; (c) repeating steps (a) and (b) until a kink is detected in the optical fiber by determining if a difference between the current signal value for the light signal of the second wavelength and the next signal value for the light signal of the second wavelength is greater than a predetermined limit; and (d) calculating a true level of the parameter that compensates for the kink at each data point based on a linear relationship existing between the current signal values for the light signal of the first wavelength and the light signals of the second wavelength, and the next signal values for the light signals of the first wavelength and the light signals of the second wavelength when the kink is detected in step (c). - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification