Abstract:
A fiber includes M primary cores and N redundant cores, where M an integer is greater than two and N is an integer greater than one. Interferometric circuitry detects interferometric pattern data associated with the M primary cores and the N redundant cores when the optical fiber is placed into a sensing position. Data processing circuitry calculates a primary core fiber bend value for the M primary cores and a redundant core fiber bend value for the N redundant cores based on a predetermined geometry of the M primary cores and the N redundant cores in the fiber and detected interferometric pattern data associated with the M primary cores and the N redundant cores. The primary core fiber bend value and the redundant core fiber bend value are compared in a comparison. The detected data for the M primary cores is determined reliable or unreliable based on the comparison. A signal is generated in response to an unreliable determination.
Abstract:
An optical force sensor along with an optical processing apparatus and method are disclosed. The optical force sensor includes an optical fiber, a core included in the optical fiber, an instrument including the optical fiber, the instrument having a distal region, and a tubular structure encasing an end of the optical fiber and secured to the first conduit at the distal region of the instrument. When an optical interferometric system is coupled to the optical fiber, it processes reflected light from a portion of the core included within the tubular structure that does not include Bragg gratings to produce a measurement of a force present at the distal region of the instrument.
Abstract:
Mechanical parameters of an object subjected to a force or condition are measured. A curved portion of a multicore optical fiber is attached to the object, and the multicore optical fiber includes a center core and plural off-center cores. A distributed, optically-based sensing technique is used to obtain information at each of multiple points along the curved portion from multiple ones of the cores of the multicore optical fiber. A curvature associated with the fiber attached to the object is determined using the information obtained from multiple ones of the cores. Strain information is obtained for the center core without having to obtain strain information for the off-center cores. Mechanical parameters are determined based on the strain information obtained for the center core and the curvature information obtained from the multiple ones of the cores.
Abstract:
An optical frequency domain reflectometry (OFDR) measurement is produced from an OFDR apparatus that includes a tunable laser source coupled to a sensing interferometer and a monitor interferometer. The sensing interferometer is also coupled to a waveguide, e.g., an optical sensing fiber. Sensor interferometric data obtained by the OFDR measurement is processed in the spectral domain (e.g., frequency) with one or more parameters to compensate for the optical dispersion associated with the sensing interferometer data. A Fourier Transform of the dispersion-compensated sensing interferometric data in the spectral domain is performed to provide a dispersion-compensated OFDR measurement information in the temporal (e.g., time) domain.
Abstract:
One or more modal characteristics are determined for a waveguide that supports more than two modes. In an example implementation, optical frequency domain reflectometry (OFDR) is used to couple light into the waveguide and detect Rayleigh scatter reflections associated with a segment of the waveguide. An original set of Rayleigh scatter data associated with the detected Rayleigh scatter reflections is generated. In addition, a scaled set of Rayleigh scatter data associated with the detected Rayleigh scatter reflections is generated. The original set of Rayleigh scatter data is correlated with the scaled set of Rayleigh scatter data. One or more modal characteristics of the waveguide are determined based on the correlation.
Abstract:
Mechanical parameters of an object subjected to a force or condition are measured. A curved portion of a multicore optical fiber is attached to the object, and the multicore optical fiber includes a center core and plural off-center cores. A distributed, optically-based sensing technique is used to obtain information at each of multiple points along the curved portion from multiple ones of the cores of the multicore optical fiber. A curvature associated with the fiber attached to the object is determined using the information obtained from multiple ones of the cores. Strain information is obtained for the center core without having to obtain strain information for the off-center cores. Mechanical parameters are determined based on the strain information obtained for the center core and the curvature information obtained from the multiple ones of the cores.
Abstract:
A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.
Abstract:
An accurate measurement method and apparatus using an optical fiber are disclosed. A total change in optical length in an optical core in the optical fiber is determined that reflects an accumulation of all of the changes in optical length for multiple segment lengths of the optical core up to a point on the optical fiber. The total change in optical length in the optical core is provided for calculation of an average strain over a length of the optical core based on the detected total change in optical length.
Abstract:
An optical sensor includes an optical fiber inscribed with a repeated refraction pattern such that light scattered from a location on the optical fiber is scattered at multiple frequencies in a range of frequencies. The inscribed patterns overlap at every measurement point along at least a portion of the length of the sensor. An optical sensing system including control circuitry coupled to the optical fiber detects measurement scatter data from the optical fiber over the range of frequencies, determines a change in the detected measurement scatter data over the range of frequencies, and extracts a parameter describing a state of the optical fiber from the determined change in the detected measurement scatter data. The sensor may be made by inscribing a first light refracting pattern on the optical fiber at every measurement point along at least a portion of the length of the sensor and inscribing a second light refracting pattern on the optical fiber that overlaps the first inscribed light refracting pattern at every measurement point along at least that portion of the length of the sensor.
Abstract:
An optical interrogation system, e.g., an OFDR-based system, measures local changes of index of refraction of a sensing light guide subjected to a time-varying disturbance. Interferometric measurement signals detected for a length of the sensing light guide are transformed into the spectral domain. A time varying signal is determined from the transformed interferometric measurement data set. A compensating signal is determined from the time varying signal which is used to compensate the interferometric measurement data set for the time-varying disturbance. The compensation technique may be applied along the length of the light guide.