In an optical fiber monitoring system which detects physical disturbance or other parameters such as temperature or strain of a fiber where a monitor signal is transmitted along the optical fiber and analyzed to detect changes which are indicative of an event, a method is provided for periodically checking proper operation of the optical fiber monitoring system. A fiber disturbance actuator periodically causes a pattern of disturbances of a portion of the fiber at a predetermined location thereon where the disturbance is characteristic of the event to be monitored. The monitor signal is analyzed to detect the pattern of changes and in the event that expected changes are not detected, a warning is issued that the intrusion detection system is not properly operating.

A method of optical sensing comprises coupling an excitation optical signal into a first optical fiber to induce Rayleigh backscattering, thereby providing a backscattered signal. The backscattered signal is optically amplified in the first optical fiber, thereby providing an amplified backscattered signal. The amplified backscattered signal is coupled into a second optical fiber and is optically re-amplifying in the second optical fiber.

An optical sensing fiber includes multiple reference reflectors spaced along a length of the fiber. Each of the multiple reference reflectors producing a reference scattering event having a known scattering profile including an elevated amplitude relative to scattering detected for neighboring segments of the optical fiber. Each of the segments is a length of contiguous fiber that is useable to initialize and perform a distributed Optical Frequency Domain Reflectometry (OFDR) sensing operation. An OFDR interrogation system is disclosed that measures a parameter using the optical sensing fiber.

In some embodiments, an apparatus and a system, as well as a method and an article, may operate to acquire a monitoring output from a first distributed feedback (DFB) fiber laser sensor at least partially bonded to a piezoelectric portion of a downhole device, to demodulate the monitoring output to determine a frequency shift in a lasing frequency of the DFB fiber laser sensor, and to correlate the frequency shift to a measure of magnetic field strength to determine a strength of a downhole magnetic field. Additional apparatus, systems, and methods are disclosed.

A multi-axis force sensor is compact in that it comprises a single strand of optical fiber and a single, movable reflecting element having a reflecting surface separated from a fiber end-face by a gap, and yet is capable of measuring axially and/or laterally applied forces with high sensitivity. The force to be measured causes the reflecting surface to tilt, translate or deform. The single strand of fiber is configured to have multiple cores that carry multiple optical interrogation signals through an end-face of the fiber to incidence on the reflecting surface.

The cores are configured so that the propagation vectors of the interrogation signals, as the signals emanate from the fiber end-face, make non-perpendicular angles with that end-face. Furthermore, the cores are configured to capture a portion of the interrogation signals back-reflected from the reflecting surface. The amount of power coupled back into each core is a function of the position of the reflecting surface, which in turn is a function of the magnitude and direction of the applied force. A deformable casing to which the force is applied may surround the reflecting element, the gap and the fiber end-face.

An instrument system that includes an image capture device, an elongate body, an optical fiber and a controller is provided. The elongate body is operatively coupled to the image capture device. The optical fiber is operatively coupled to the elongate body and has a strain sensor provided on the optical fiber. The controller is operatively coupled to the optical fiber and adapted to receive a signal from the strain sensor and to determine a position or orientation of the image capture device based on the signal.

Methods of measuring an anomaly, any induced change in physical parameters such as strain, temperature, and so forth, in an optical fiber. One method may include launching a plurality of probe pulses from a probe source; recording a Brillouin scattering spectrum from a plurality of reflection signals generated in the optical fiber, responsive to the plurality of probe pulses; determining a relative motion between the optical fiber and the anomaly during the recording the Brillouin back-scattering spectrum; and dynamically adjusting the Brillouin back-scattering spectrum according to the relative motion, or performing an adjustment of the Brillouin back-scattering spectrum after acquisition of the Brillouin back-scattering spectrum.

A control system for a variable area fan nozzle (VAFN) having a plurality of petals is disclosed. The control system may include at least one fiber optic shape sensor extending along at least one of the plurality of petals, and a light source operatively connected to the at least one fiber optic shape sensor. The control system may further include a receiver operatively connected to the at least one fiber optic shape sensor. The control system may further include a VAFN control unit in operative communication with the plurality of petals and the receiver. The VAFN control unit may be configured to receive a signal from the receiver indicative of the measured strain along the at least one fiber optic shape sensor, and calculate a nozzle area of the VAFN based on the measured strain.

Disclosed are a Fabry-Perot sensor and a method for manufacturing the same. A Fabry-Perot sensor including: a base part; a cavity formed between the base part and a pressure-sensitive film, and enclosed by the base part and the pressure-sensitive film; the pressure-sensitive film, fixed to the base part, wherein the pressure-sensitive film has one or more localised areas, each localised area has a doping substance doped into a base material of the pressure-sensitive film to produce stress, no localised area penetrates the entire thickness of the pressure-sensitive film, and under the effect of stress, the pressure-sensitive film has a corrugated structure; an optic fibre used for conducting a light signal, one end part of the optic fibre being fixed to an optic fibre mounting part of the base part, and the optic fibre mounting part being located at an end part of the base part opposite the cavity.

A sensor that can be used for real time monitoring of load and structural health in engineering structures is provided. The sensor may include a patch with a portion of an optical fiber embedded therein. There may also be triboluminescent materials dispersed within the patch, on and/or near the portions of the optical fiber embedded in the patch. There may be micro-excitors located in proximity to the triboluminescent materials and on the surface of the optical fiber. Loading events and/or damage to the monitored structure may result in a triboluminescent emission from the triboluminescent material that can be guided via the optical fiber. Analysis of the triboluminescent emission may provide information on the magnitude of the applied load as well as the occurrence, severity and location of damage in the structure.