A pressure measuring device 30 installs on a tube 11 for transferring a medium BL so as to measure a pressure of the medium BL inside the tube 11. The pressure measuring device 30 includes a main body portion 31 mountable to the tube 11, polarizing means 34 disposed in the main body portion 31 so that light oscillating in a specific direction is transmitted therethrough, an image acquisition unit 32 disposed in the main body portion 31 so that image information on a pressure receiver that is deformed in response to the received pressure is acquired through the polarizing means 34, and a control unit 100 that converts the image information acquired by the image acquisition unit 32 into pressure information about the pressure.

To sense the shape of a multicore optical fiber sensor, light reflected in a center and two or more helixed outer cores of the optical fiber sensor is measured, and phases associated with strain in the center and helixed outer cores is tracked along the length of the fiber sensor. Further, a wobble signal indicative of a variation in the spin rate of the fiber sensor is determined. Based on the tracked phases and the wobble signal, the fiber shape is computed.

The invention discloses an apparatus for measuring the torsion between a first point (41) and a second point (42) of a test object (1), said second point being spaced apart from the first point. The apparatus comprises the following: a source of polarized light, comprising a polarizing light source (15) that emits polarized light, or a polarizer (20) that is connected to a light source (10) by way of an optical feed; a first optical fibre (40) that is optically connected to the Output of the polarizing light source (15) or to the Output of the polarizer (20) and that is fastened to the test object (1) at the first point (41) and at the second point (42) in such a way that a torsion of the test object about a torsion axis causes a change in the angle of rotation of the first optical fibre from the first point in relation to the second point, and a second polarization-maintaining optical fibre (50), that is connected to the first optical fibre (40) at the second point (42) or downstream of the second point (42) in relation to the light path Coming from the source, for supplying the light to a measuring device (30, 31), wherein the distance between the first point (41) and the second point (42) of the test object (1) is greater than or equal to 5 metres, or greater than or equal to 7 metres, or greater than or equal to 10 metres, and the first optical fibre (40) comprises a non-polarization-maintaining, bending-insensitive fibre.

A method of measuring strain includes providing laminated material having ply layers, and a thickness along a direction orthogonal to the ply layers, and a strain sensor embedded between adjacent ply layers, wherein: the strain sensor includes first and second planar optical waveguide, each of the waveguides having a waveguiding core defining an optical propagation direction parallel to the laminated material and a Bragg grating in the waveguiding core, the optical propagation directions of the optical waveguides being non-parallel; interrogating the first optical waveguide Bragg grating with transverse electric (TE) and transverse magnetic (TM) polarized light, to obtain a TE spectral response and a TM spectral response; interrogating the second optical waveguide Bragg grating with TE and TM polarized light to obtain a TE spectral response and a TM spectral response; and processing the TE spectral responses and the TM spectral responses to extract a through-thickness component of strain.

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.

A polarized image acquisition section 20 acquires a plurality of polarized images having different polarization directions. The polarized images show, for example, an input indicator for a user interface as a recognition target object. A normal line calculation section 30 calculates normal lines for individual pixels of the recognition target object in accordance with the polarized images acquired by the polarized image acquisition section 20. The normal lines represent information based on the three-dimensional shape of the recognition target object. A recognition section 40 recognizes the object by using the normal lines calculated by the normal line calculation section 30, determines, for example, the type, position, and posture of the input indicator, and outputs the result of determination as input information on the user interface. The object can be recognized easily and with high accuracy.

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.

The present invention discloses a distributed device for simultaneously measuring strain and temperature based on optical frequency domain reflection, comprising a tunable laser, a 1:99 beam splitter, a main interferometer system, a light source phase monitoring system based on an auxiliary interferometer, an acquisition device and a computer processing unit, wherein the main interferometer system comprises two Mach-Zehnder interferometers, and two optical fibers having different cladding diameters are arranged in parallel as sensing fibers. Due to the difference in temperature and strain coefficients of optical fibers of the same diameter, the temperature and strain values during changing the temperature and strain simultaneously can be obtained by matrix operation, thereby achieving an effect of eliminating cross sensitivity of temperature and strain sensing in optical frequency domain reflection.

A method of predicting the gravity-free shape of a glass sheet and a method of managing the quality of a glass sheet based on the gravity-free shape of the glass sheet. The initial shape of a glass sheet is determined. When the glass sheet is flattened, values of stress at a plurality of locations in the glass sheet are obtained. A shape that the glass sheet will have when the flattened glass sheet is deformed such that the values of stress are zero is predicted as a stress-induced shape and a gravity-free shape of the glass sheet is predicted by combining the initial shape and the stress-induced shape. Quality management is performed on glass sheets based on gravity-free shapes thereof predicted using the method of predicting the gravity-free shape of a glass sheet.

A fiber Bragg grating interrogator assembly, comprising: an optical fiber including a fiber Bragg grating (FBG; 122) having a variable Bragg wavelength (.sub.B) and a dynamic range of interest (.sub.dyn,B) over which the Bragg wavelength (.sub.B) can shift during use; a light source operably connected to the optical fiber, and configured to illuminate the fiber Bragg grating to solicit a response therefrom; and an response analyzer, including: a spectrally selective device having an input port and a plurality of output ports (149-n), wherein the input port is operably connected to the optical fiber and wherein each of the output ports is associated with a respective spectral range (.sub.n), said spectrally selective device being configured to provide a spectral energy distribution of a response of the fiber Bragg grating received on the input port onto said output ports.