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.

The present invention is a method for measuring the deformation of a subsea pipeline (1), wherein an electromagnetic wave is emitted towards subsea pipeline (1), the electromagnetic wave being reflected by a metal layer (2) of subsea pipeline (1) and the reflected electromagnetic wave being analysed to deduce the deformation of subsea pipeline (1).

The present disclosure provides a device that accurately measures vibration at a designated position of a sensing fiber without using digital signal processing to compensate for distance fluctuation. Digital signal processing for correcting fluctuation of a measurement distance due to a frequency offset of a beat signal due to vibration, which is a measurement target, is simplified. In the present disclosure, vibration at a designated position of the sensing fiber is accurately measured without using the digital signal processing to compensate for the distance fluctuation. A spectrum analysis length of an electrical field E(τn) of backscattered light is set to be larger than a delay deviation N.sub.d due to frequency modulation caused by dynamic strain. An index of tolerance of vibration distribution measurement to the delay deviation N.sub.d is also clarified.

An optical fiber includes multiple optical cores configured in the fiber including a set of primary cores and an auxiliary core. An interferometric measurement system uses measurements from the multiple primary cores to predict a response from the auxiliary core. The predicted auxiliary core response is compared with the actual auxiliary core response to determine if they differ by more than a predetermined amount, in which case the measurements from the multiple primary cores may be deemed unreliable.

There is described a method for interrogating optical fiber comprising fiber Bragg gratings (“FBGs”), using an optical fiber interrogator. The method comprises (a) generating an initial light pulse from phase coherent light emitted from a light source, wherein the initial light pulse is generated by modulating the intensity of the light; (b) splitting the initial light pulse into a pair of light pulses; (c) causing one of the light pulses to be delayed relative to the other of the light pulses; (d) transmitting the light pulses along the optical fiber; (e) receiving reflections of the light pulses off the FBGs; and (f) determining whether an optical path length between the FBGs has changed from an interference pattern resulting from the reflections of the light pulses.

Shape-sensing systems and methods for medical devices. The shape-sensing system can include a medical device, an optical interrogator, a console, and a display screen. The medical device can include an integrated optical-fiber stylet having fiber Bragg grating (“FBG”) sensors along at least a distal-end portion thereof. The optical interrogator can be configured to send input optical signals into the optical-fiber stylet and receive FBG sensor-reflected optical signals therefrom. The console can be configured to convert the reflected optical signals with the aid of filtering algorithms of some optical signal-converter algorithms into plottable data for displaying plots thereof on the display screen. The plots can include a plot of curvature vs. time for each FBG sensor of a selection of the FBG sensors for identifying a distinctive change in strain of the optical-fiber stylet as a tip of the medical device is advanced into a superior vena cava of a patient.

An apparatus for monitoring strain in an optical chip in silicon photonics platform. The apparatus includes a silicon photonics substrate shared with the optical chip. Additionally, the apparatus includes an optical input configured in the silicon photonics substrate to supply an input signal of a single wavelength. The apparatus further includes a first waveguide arm and a second waveguide arm embedded in the silicon photonics substrate to form an on-chip interferometer. The second waveguide arm forms a delay line being disposed at a region in or adjacent to the optical chip. The on-chip interferometer is configured to generate an interference pattern serving as an indicator of strain distributed at the region in or adjacent to the optical chip. The interference pattern is caused by a temperature-independent phase shift at the single wavelength of the interferometer between the first waveguide arm and the second waveguide arm.

A system for sensing microbends and micro-deformations in three-dimensional space is based upon a distributed length optical fiber formed to include a group of offset cores disposed in a spiral configuration along the length of the fiber, each core including a fiber Bragg grating that exhibits the same Bragg wavelength. A micro-scale local deformation of the multicore fiber produces a local shift in the Bragg wavelength, where the use of multiple cores allows for a complete micro-scale modeling of the local deformation. Sequential probing of each core allows for optical frequency domain reflectometry (OFDR) allows for reconstruction of a given three-dimensional shape, delineating location and size of various microbends and micro-deformations.

An optical fiber includes multiple optical cores configured in the fiber including a set of primary cores and an auxiliary core. An interferometric measurement system uses measurements from the multiple primary cores to predict a response from the auxiliary core. The predicted auxiliary core response is compared with the actual auxiliary core response to determine if they differ by more than a predetermined amount, in which case the measurements from the multiple primary cores may be deemed unreliable.

An optical fiber includes multiple optical waveguides configured in the fiber. An interferometric measurement system mitigates or compensates for the errors imposed by differences in a shape sensing optical fiber's response to temperature and strain. A 3-D shape and/or position are calculated from a set of distributed strain measurements acquired for a multi-core optical shape sensing fiber that compensates for these non-linear errors using one or more additional cores in the multicore fiber that react differently to temperature changes than the existing cores.