A monitoring system includes optical sensors disposed on one or more fiber optic waveguides. Each optical sensor is spaced apart from other optical sensors and is disposed at a location along a route defined by a transportation structure that supports a moveable conveyance. The plurality of optical sensors are mechanically coupled to one or both of the transportation structure and the moveable conveyance. Each optical sensor provides an optical output signal responsive to vibrational emissions of one or both of the transportation structure and the conveyance. The monitoring system includes a detector unit configured to convert optical output signals from the optical sensors to electrical signals. A data acquisition controller synchronizes recordation of the electrical signals with movement of the conveyance.

An optical fiber changes a polarization state of a propagating light when at least one of a vibration and a displacement occurs. An optical transmitter inputs a first wavelength light to the optical fiber via a separator, and an optical transmitter inputs a second wavelength light to the optical fiber via a separator. The first and second wavelength lights propagated through the optical fiber in mutually opposite directions are respectively received by optical receivers (13 and 12) via the separators (18 and 17), and a fluctuation of a polarization is detected in polarization fluctuation detectors (16 and 15). A data processing device collects data indicating the fluctuation of the polarization detected by the polarization fluctuation detector and data indicating the fluctuation of the polarization detected by the polarization fluctuation detector.

This application describes methods and apparatus for fibre optic sensing. A receive unit includes an optical arrangement configured to receive coherent optical radiation that has propagated through a sensing optical fibre and to form first and second optical signals, wherein the second optical signal comprises optical radiation received from the sensing optical fibre later than the optical radiation of the first optical signal by a defined time period. A photodetector detects the first optical signal mixed with the second optical signal and a processor demodulates a derivative signal formed by interference of the first and second optical signals. First and second receive units may be located at opposite ends of a cable structure to provide respective measurement signals and a signal processor can process the two measurement signals to locate a disturbance.

A bonded structure includes a first member, a second member, an adhesive that bonds the first member and the second member together, and an optical fiber sandwiched between the first member and the second member. When pressure is applied to the optical fiber only from a predetermined direction, the sectional shape of the optical fiber changes to an elliptical shape, so that birefringence occurs, whereby the shape of the light spectrum changes so as to have multiple peaks. The optical fiber is used as a sensor for detecting the bonding condition between the first member and the second member based on the birefringence.

The optical fiber sensor device comprises a probe light supply unit, an optical fiber sensor unit, and a polarization state measuring unit. The probe light supply unit generates and outputs a polarization switched light beam by alternately switching a polarized CW light beam in polarization directions orthogonal to each other with elapse of time. The optical fiber sensor unit includes a loop-state optical fiber into which the polarization switched light beam is input and which outputs a light wave reflecting a change of birefringence according to a stress applied from an outside in the polarization switched light beam. The polarization state measuring unit observes polarization states of the respective light waves propagating clockwise and counterclockwise through the optical fiber. The polarization state measuring unit calculates an angular velocity vector .sub.b defined by an equation that specifies a relationship between a temporal change rate ds.sub.out(t)/dt of a Stokes vector s.sub.out(t) giving a polarization state of the light wave from the optical fiber and the Stokes vector s.sub.out(t) for each of the clockwise and counterclockwise light waves. The angular velocity vector .sub.b gives a direction of a rotation center axis and a rotation angular velocity of the Stokes vector s.sub.out(t).

A monitoring system includes optical sensors disposed on one or more fiber optic waveguides. Each optical sensor is spaced apart from other optical sensors and is disposed at a location along a route defined by a transportation structure that supports a moveable conveyance. The plurality of optical sensors are mechanically coupled to one or both of the transportation structure and the moveable conveyance. Each optical sensor provides an optical output signal responsive to vibrational emissions of one or both of the transportation structure and the conveyance. The monitoring system includes a detector unit configured to convert optical output signals from the optical sensors to electrical signals. A data acquisition controller synchronizes recordation of the electrical signals with movement of the conveyance.

A shape calculating apparatus includes a light source, an optical fiber provided with detection targets. The detection targets have mutually different light absorption spectra to decrease a quantity of light propagated by the fiber in accordance with a bend shape of the fiber. The apparatus also includes a light detector to detect light quantity information at wavelengths included in the light absorption spectra, a calculator to execute a calculation relating to a shape of each detection target based on the light quantity information. The apparatus further includes a setting change unit to change, with respect to each of the wavelengths, a dynamic range of at least either an intensity of light input to the optical fiber or an electric signal generated by the detector.

The approach relates to a procedure for determining a signal transmission quality of a light transmission path, which consists of a light transmitter on one end and a light receiver on its other end. A transmitter code is received in a first step. The transmitter code hereby represents a signal which is transmitted from the light transmitter to the light receiver. In a further step the receiver code is read in. The receiver code hereby represents a signal which was provided by the light receiver by using the transmitter code. The determining of a degree of correspondency between the transmitter code and the receiver code is performed in a final step of determining, in order to define the signal transmission quality of the light transmission path.

The optical fiber sensor device comprises a probe light supply unit, an optical fiber sensor unit, and a polarization state measuring unit. The probe light supply unit generates and outputs a polarization switched light beam by alternately switching a polarized CW light beam in polarization directions orthogonal to each other with elapse of time. The optical fiber sensor unit includes a loop-state optical fiber into which the polarization switched light beam is input and which outputs a light wave reflecting a change of birefringence according to a stress applied from an outside in the polarization switched light beam. The polarization state measuring unit observes polarization states of the respective light waves propagating clockwise and counterclockwise through the optical fiber. The polarization state measuring unit calculates an angular velocity vector .sub.b defined by an equation that specifies a relationship between a temporal change rate ds.sub.out(t)/dt of a Stokes vector s.sub.out(t) giving a polarization state of the light wave from the optical fiber and the Stokes vector s.sub.out(t) for each of the clockwise and counterclockwise light waves. The angular velocity vector .sub.b gives a direction of a rotation center axis and a rotation angular velocity of the Stokes vector s.sub.out(t).

Fiber optic sensors based on multicore optical fibers that are intended for use in harsh environment sensing. This multicore fiber comprises an arrangement of optically coupled cores in a silica background. Sensors are fabricated by splicing a section of multicore fiber between two single mode fibers. This multicore fiber sensor is simple and repeatable to fabricate and multiple sensors can be multiplexed in a chain. These fiber optic sensors are intended for a broad set of sensing applications including temperature, pressure, strain, bending, acoustic vibrations, mechanical vibrations, or combinations thereof.