Abstract: A BOTDA system that combined optical pulse coding techniques and coherent detection includes a narrow linewidth laser, two polarization-maintaining couplers, microwave generator, two electro-optic modulators (EOMs), fiber under test, an optical circulator, a 3 dB coupler, a polarization scrambler, a pulse generator, a balance photodetector, an electrical spectrum analyzer, digital signal processing unit and a frequency shifter. The optical pulse coding techniques and coherent detection are simultaneously used in the invented system, which can be enhance the signal-to-noise ration (SNR), the measuring accuracy and the sensing distance of BOTDA. Moreover, the proposed system has the capacity of break interrogation.

Abstract: A cable for distributed fibre optic sensing comprising a flexible tape, an optical fibre suitable for Brillouin scattering measurement forming at least two lengths, and at least one free end of at least one length being connectable to a reading unit, wherein at least a section of the longitudinal length of the flexible tape is situated between at least a section of the two lengths such that the two lengths are in close proximity such that a temperature gradient between the two lengths is minimized, and wherein the section of the tape and the section of lengths can flex together.

Abstract: A system, device and method include a sensing enabled device (104) having at least one optical fiber (126) configured to sense induced strain. An interpretation module (115) is configured to receive signals from the at least one optical fiber interacting with a volume and to interpret the signals to determine positions visited by the at least one optical fiber within the volume. A storage device (116) is configured to store a history of the positions visited in the volume.

Abstract: In certain embodiments, an optical device and a method of use is provided. The optical device can include a fiber Bragg grating and a narrowband optical source. The narrowband optical source can be configured to generate light. A first portion of light can be transmitted along a first optical path extending along and through the length of the fiber Bragg grating at a group velocity. The light can have a wavelength at or in the vicinity of a wavelength at which one or more of the following quantities is at a maximum value: (a) the product of the group index spectrum and a square root of the power transmission spectrum, (b) the slope of a product of the group index spectrum and one minus the power transmission spectrum, and (c) the slope of a product of the group index spectrum and the power transmission spectrum.

Abstract: A strain gauge or other device may include a deformable medium and discrete plasmon supporting structures arranged to create one or more plasmon resonances that change with deformation of the medium and provide the device with an optical characteristic that indicates the deformation of the medium.

Abstract: A motor assembly for a submersible pump which includes capability of detecting or monitoring one or more operating parameters for the motor, including temperature, pressure and strain.

Abstract: An optical shear sensor that includes a first and second outer surface at opposing sides and a sensing element is disclosed. In one aspect, the sensing element has an optoelectronic source for emitting light of a predetermined wavelength and having a source front surface where light exits the optoelectronic source, and a photodetector for detecting light of the predetermined wavelength and having a detector front surface where light of the optoelectronic source is received. The optoelectronic source is positioned along the first outer surface and emits light towards the second outer surface. A flexible sensing layer transparent to the predetermined wavelength covers the front surface of the optoelectronic source and the front surface of the photodetector. Upon application of a shear stress, the sensing layer deforms elastically and the outer surfaces are displaced along directions parallel to each other and the source front surface so the intensity of light detected by the photodetector changes.

Abstract: A material is illuminated with one or more light sources including at least one light source which emits light of controlled coherence properties. Both of a spectral characteristic and a speckle statistic are derived using light reflected from the illuminated material. The spectral characteristic and the speckle statistic are compared against plural entries in a database. Each entry in the database correlates the identity of a material against a corresponding spectral characteristic and a corresponding speckle statistic for the material. At least one candidate for the identity of the illuminated material is determined based at least in part on the comparison.

Abstract: An aging apparatus including a pulse laser, a beam expansion assembly, and a platform configured to carry an object is provided. The pulse laser transmits a first beam to the beam expansion assembly. The beam expansion assembly expands the first beam to a second beam and projects the second beam onto the object.

Abstract: A system and method for monitoring bending curvature of a flexible pipe structure, including at least one conduit configured to conform to a profile of a bend stiffener of a flexible pipe structure, and the at least one conduit including one or more sensors, wherein each sensor is configured for measuring a bending curvature of the bend stiffener.

Abstract: The present disclosure is generally directed to a strain sensor, system and method of fabrication and use that includes an optical fiber, an optical signal generator that transmits an optical signal through the optical fiber, at least two photonic crystal slabs within the optical fiber separated by a first segment of optical fiber, a photo-detector that detects a reflected optical signal from the at least two photonic crystal slabs, and a processor that computes a mechanical strain over the first segment of optical fiber based on the reflected optical signal detected by the photo-detector.

Abstract: The structural material with embedded sensors provides of diagnostics and measurement of static and/or dynamic strains in structures and structural elements formed from the structural material. The structural material includes an array of fiber Bragg grating sensors or the like embedded therein for strain measurement and monitoring. An array of linear channels is formed in the structural element, and the plurality of fiber Bragg grating sensors are respectively disposed therein. The plurality of fiber Bragg grating sensors communicate with a signal analyzer, which receives the signals generated by the fiber Bragg grating sensors, the signals being representative of a magnitude of a strain placed on the structural element. The signal analyzer may, in turn, transmit a conditioned signal to a computer or the like for presentation of strain data to the user.

Abstract: The invention provides a method of obtaining the FBG data in final form (transforming the raw data into frequency and location data) by taking the raw FBG sensor data and dividing the data into a plurality of segments over time. By transforming the raw data into a plurality of smaller segments, processing time is significantly decreased. Also, by defining the segments over time, only one processing step is required. By employing this method, the refresh rate of FBG sensor systems can be improved from about 1 scan per second to over 20 scans per second.

Abstract: A monitoring and management system (MMS) includes one or more fiber optic cables arranged within or on portions of an energy storage device. Each fiber optic cable includes multiple optical sensors. At least one of the optical sensors is configured to sense a parameter of the energy storage device that is different from a parameter of the energy storage device sensed by at least another optical sensor of the multiple optical sensors. The MMS includes a light source configured to provide light to the one or more fiber optic cables and a detector configured to detect light reflected by the optical sensors. The detector generates an electrical signal based on the reflected light. A processor is coupled to receive the electrical signal, to analyze the electrical signal, and to determine state of the energy storage device based on analysis of the electrical signal.

Abstract: A force sensing apparatus and an operating method of the force sensing apparatus may obtain and provide information about a force applied to an object, thereby enabling control of a force to be applied to manipulate the object.

Abstract: In an FBG (Fiber Bragg Grating) sensor, a stress direction converter includes a flat portion to which stresses are applied from the exterior, and stress transmitting sections that are bridged from the flat portion to an optical fiber cable. An inclined portion of the optical fiber cable, through which reflected light reflected by gratings is transmitted, is disposed along an inclined section that makes up one of the stress transmitting sections.

Abstract: A Brillouin analysis sensor system comprising: a Brillouin analysis sensor; a polarization beam splitter/combiner, operably connected to the Brillouin analysis sensor between the sensor and the sensing fiber, for receiving polarized lightwaves from the sensor, combining the lightwaves and launching combined lightwaves waves in the sensing fiber a first direction, and a phase conjugate mirror at a free end of the sensing fiber for receiving combined lightwaves from the polarization beam splitter/combiner, rotating the polarization of the combined lightwaves and launching the rotated combined lightwaves in the sensing fiber in an opposing direction to the first direction.

Abstract: The structural material with embedded sensors provides of diagnostics and measurement of static and/or dynamic strains in structures and structural elements formed from the structural material. The structural material includes an array of fiber Bragg grating sensors or the like embedded therein for strain measurement and monitoring. An array of linear channels is formed in the structural element, and the plurality of fiber Bragg grating sensors are respectively disposed therein. The plurality of fiber Bragg grating sensors communicate with a signal analyzer, which receives the signals generated by the fiber Bragg grating sensors, the signals being representative of a magnitude of a strain placed on the to structural element. The signal analyzer may, in turn, transmit a conditioned signal to a computer or the like for presentation of strain data to the user.

Abstract: A system for measuring thin film stress, anisotropic or isotropic, such as from thin film deposition onto semiconductor substrates found in semiconductor manufacturing. The system uses resettled volume difference, V2?V1, of the surface of a material to calculate stress. The system includes a means to collect 3D surface points, a method to calculate volume and a method to calculate thin film stress from resettled volume difference. Calculating stress from resettled volume difference, V2?V1, eliminates the inaccuracy of calculating stress from the change in surface curvature or surface radius with equations such as ( 1 R 2 - 1 R 1 ) . The inaccuracy of stress calculated from surface curvature is from the non-spherical deformation of anisotropic materials, such as semiconductor substrates, eg: silicon wafers in semiconductor manufacturing.

Abstract: A system and method for post-tensioned tendon monitoring includes at least one optical sensor arranged in monitoring proximity to a post-tensioned tendon, a test instrument in communication with the optical sensor, and a processor capable of managing operation of the test instrument, a storage device and a display. The system and method further include a database adapted to contain sensor baseline information and sensor measurement data. The test instrument is capable of sending a first wavelength to the optical sensor and receiving a second wavelength from the optical sensor, wherein at least one of the instrument or the processor is configured to analyze the second wavelength and output sensor measurement data for storage in the database. The processor is configured to calculate an amount of tensile loading which exists in the post-tensioned tendon, based on the sensor measurement data and the sensor baseline data, and to provide an output.

Abstract: A curvature sensing device 10 comprising, a first fiber Bragg grating (FBG) strain sensor 12, a second FBG strain sensor 14, a flexible piece comprising two end pieces 16, 18 joined by a tubular mid-section 20. The device 10 further comprises 16 contact rollers 22 provided on the internal surfaces of the end pieces 16, 18, which maintain the end pieces 16, 18 tangential to a pipe around which the device 10 is located. The FBG strain sensors 12, 14 are embedded within the mid-section 20 and are arranged in two generally orthogonal planes, so that the curvature is measured in two dimensions. This enables the device 10 to detect both the magnitude and direction of bending/curvature within a pipe. Bending in a pipe is transferred through the end pieces 16, 18 to the mid-section 20. The FBG sensors 12, 14 measure bending of the mid-section 20 from which bending of the pipe can be inferred.

Abstract: A current transformer (5) having a plurality of primary and secondary windings, comprising a top Strain measuring system of wind turbine blades (11) during the performance of static tests that comprises an equipment for measuring the strain at multiple locations in mono-mode optical fibers (5, 7, 9) using Rayleigh scattered light, that includes an OBR interrogator (23), an interface device (25) and an Acquisition System (27), said mono-mode optical fibers (5, 7, 9) being attached to the blade (11) subjected to said tests for obtaining high spatial resolution measurements of the blade strain during said tests. Said optical fibers (5, 7, 9) may be placed whether in a longitudinal direction or in a non-longitudinal direction or in a non-linear shape in given blade sections and may be bonded whether to the outer skin (31) of the blade (11), or into grooves (51, 53) in the outer skin (31) of the blade (11) or embedded between two structural laminates (33, 35) of the blade (11).

Abstract: A computer-implemented method for measuring full field deformation characteristics of a deformable body. The method includes determining optical setup design parameters for measuring displacement and strain fields, and generating and applying a dot pattern on a planar side of a deformable body. A sequence of images of the dot pattern is acquired before and after deformation of the body. Irregular objects are eliminated from the images based on dot light intensity threshold and the object area or another geometrical cutoff criterion. The characteristic points of the dots are determined, and the characteristic points are matched between two or more of the sequential images. The displacement vector of the characteristic points is found, and mesh free or other techniques are used to estimate the full field displacement based on the displacement vector of the characteristic points. Strain tensor or other displacement-derived quantities can also be estimated using mesh-free or other analysis techniques.

Abstract: A medical device calibration apparatus, system and method include a calibration template (202) configured to position an optical shape sensing enabled interventional instrument (102). A set geometric configuration (206) is formed in or on the template to maintain the instrument in a set geometric configuration within an environment where the instrument is to be deployed. When the instrument is placed in the set geometric configuration, the instrument is calibrated for a medical procedure.

Abstract: A pressure sensor (10) comprising fiber Bragg grating (FBG) strain sensors (12) provided within an optical fiber (14), an optical fiber strain sensor carrier rod 16 and a pressure intensifying sleeve (18). The carrier rod (16) is formed from a first glass fiber reinforced epoxy resin composite material having a first stiffness/elastic modulus the direction of strain sensing. The sleeve (18) is formed from a second composite material, having a lower axial stiffness in the direction of strain sensing than that of the carrier rod (16). Under an applied hydrostatic load, the sleeve (18) exerts an axial compressive load onto the section of rod (16) within the sleeve (18). The axial compressive strain experienced by the rod (16) is thereby increased in the region within the sleeve (18) compared to the axial compressive strain that would be produced in the rod (16) if the sleeve (18) was not present.

Abstract: An optical fiber crack detector that includes a plurality of FBG sensors positioned within one or more fibers that are operable to reflect a defined wavelength of an optical input beam. The crack detector includes a light source for generating the optical input beam that propagates down the optical fiber and interacts with the FBG sensors. A wavelength of the optical beam that is reflected by the FBG sensors is detected, and if a crack in the component damages the fiber between an FBG sensor and the detector circuit, where one or more of the reflected signals are not received, the detector knows that a crack has occurred. By strategically placing a plurality of the FBG sensors along the fiber, a crack that damages the fiber in multiple locations between multiple FBG sensors, or in multiple fibers, can provide an indication of the length of the crack.

Abstract: According to the present invention there is provided a strain sensor apparatus comprising, two or more strain sensors each of which is capable of measuring strain and each of which is configured such that it can be arranged to cooperate with a structure to be monitored so that strain in the structure can be detected by a strain sensor, and one or more position references which is/are arranged in a predetermined position relative to the two or more strain sensors and wherein the one or more position references are each configured such that they are suitable for cooperating with a measuring means; one or more measuring means which is configured to cooperate with the one or more position references so that the angular orientation of the one or more position references can be determined. There is further provided a corresponding method for sensing strain in a structure.

Abstract: A sensor system for measuring an operating parameter of a wind turbine component is described. The fibre optic sensor system comprises a light source for outputting light in a predetermined range of wavelengths, and an optical fibre comprising a long Fibre Bragg Grating, extending continuously over a length of the optical fibre to provide a continuous measurement region in the optical fibre. The optical fibre is coupled to the wind turbine component such that the continuous measurement region is located at a region of the wind turbine component to be sensed, and such that the grating period at each location in the continuous measurement period is dependent upon the value of the operating parameter at that location. A light detector receives light from the optical fibre, and provides an output signal to the controller indicating the intensity of the received light; based on the detected light, a value for the operating parameter is determined.

Abstract: A surface layer formed of a composite material is stacked on the surface of a core layer formed of a foam synthetic resin material, and an arrester portion is provided in an interface region between the surface layer and the core layer to prevent the progression of delamination between the surface layer and the core layer. Optical fibers with grating portions are embedded inside the arrester and along the surface layer, and the spectra of reflected light from the optical fibers are compared to detect the occurrence position of a crack between the surface layer and the core layer.

Abstract: The invention relates to an optical strain gauge (1) using a glass fibre as a strain sensor. The strain gauge comprises a glass fibre comprising a sheath. The sheath has the following composition: a mixture of polyether ether ketone and an admixture of at least 10 weight percent and a maximum of 40 weight percent of an inorganic filler, with a particle size of between 0.08 ?m and 12 ?m. The outer diameter of the sheath is between 0.2 mm and 1.2 mm. The ratio D/d between the outer diameter D of the sheath and the diameter d of the glass fibre is between 2 and 6. A pressure of the sheath on the glass fibre is such that essentially no relative movement can occur between the glass fibre and the sheath.

Abstract: An FBG (Fiber Bragg Grating) sensor is equipped with a plurality of stress detection sensors made up from optical fibers in which gratings that reflect light of a specified wavelength are arrayed, and a stress direction converter that converts stresses applied from the exterior into stresses of a direction in which the gratings are arrayed, and which transmits the stresses to each of the gratings. Consequently, the stress direction converter can transmit stresses, which are applied from a body, to a plurality of gratings.

Abstract: A system and method for detecting breakage, rupture or malfunctioning of a pipe or cable structure, including sensing elements for monitoring the structure and placed in, on or around the structure for monitoring the breakage, rupture or malfunctioning of the structure. The sensing elements provide sensing data regarding events related to breakage, rupture or malfunctioning and are placed near the structure so as to perform a breakage, rupture or malfunction detection function, and within a distance sufficient to obtain a measureable strain, tension, torsion, vibration, acceleration, and/or temperature response signal based on the breakage, rupture or malfunctioning of the structure. One of the sensing elements is based on Coherent Rayleigh Noise (CRN) sensing techniques, and the system is configured to interpret the sensed data for determining the breakage, rupture or malfunctioning of the structure.

Abstract: At least one embodiment of the invention relates to a catheter arrangement comprising a catheter with a proximal section and a distal section, to measure a force acting on the distal section and simultaneously receive a temperature signal prevailing in the distal section. According to at least one embodiment of the invention, the catheter arrangement comprises an evaluation unit connected to a single combined optical force and temperature sensor, and further comprises a readout signal generator to generate and feed a readout signal modulated with a carrier frequency into the force sensor and temperature sensor. According to at least one embodiment of the invention, the catheter arrangement comprises a first readout device to read out a first modulated measuring signal portion, a second readout means to read out a second unmodulated measuring signal portion, and a processing unit to combine the first and second measuring signal portions.

Abstract: An optical measurement instrument includes a measurement head and mechanical support elements arranged to support a sample well plate. The measurement head is moved towards the sample well plate and, after the measurement head has touched the sample well plate, the measurement head is moved backwards away from the sample well plate so as to provide a desired distance between the measurement head and the sample well plate. A sensor device is attached to the mechanical support elements and arranged detect a mechanical effect occurring in the mechanical support elements due to force directed by the measurement head to the sample well plate. Hence, the situation in which the measurement head touches the sample well plate can be detected without a need to provide the measurement head with a force sensor. This is advantageous because the measurement head can be a changeable module of the optical measurement instrument.

Abstract: The present invention provides a monitoring device for detecting stresses and strains in structural components and a method of using the monitoring device. The monitoring device comprises a base material, one or more attachment points for attaching the monitoring device to a structure to be monitored, a detection zone on the monitoring device, and a means for detecting the presence of stress and strain in the detection zone. The dimensions and material of the monitoring device are chosen such that a predetermined level of strain transmitted to the monitoring device from the structure will result in a known level of stress and strain in the detection zone. Detection of stress and strain in the detection zone can be correlated to a level of stress and strain experienced by the structure at the point of attachment of the monitoring device.

Abstract: Apparatus and method for monitoring at least one parameter associated with an elongate structure are disclosed. The apparatus may include at least one elongate support body element arranged along a longitudinal structure axis associated with an elongate target structure; and at least one optic fibre element arranged substantially helically along a longitudinal body element axis associated with the at least one support body element. A method of manufacturing flexible pipe body is also disclosed.

Abstract: An optical device, a method of configuring an optical device, and a method of using a fiber Bragg grating is provided. The optical device includes a fiber Bragg grating, a narrowband optical source, and at least one optical detector. The fiber Bragg grating has a power transmission spectrum as a function of wavelength with one or more resonance peaks, each comprising a local maximum and two non-zero-slope regions with the local maximum therebetween. The light generated by the narrowband optical source has a wavelength at a non-zero-slope region of a resonance peak that is selected such that one or more of the following quantities, evaluated at the resonance peak, is at a maximum value: (a) the product of the group delay spectrum and the power transmission spectrum and (b) the product of the group delay spectrum and one minus the power reflection spectrum.

Abstract: Fiber optic monitoring of dimensional changes within a subterranean formation includes deploying a fiber optic cable assembly in a wellbore and attaching the cable assembly to first and second attachment points on either side of the formation. A surface fiber optic measurement system measures changes in the optical path length between the attachment points of the fiber optic cable assembly. The changes in optical path length are directly indicative of dimensional changes within the formation.

Abstract: A rotor blade monitoring system for use with a wind turbine. The wind turbine includes at least one rotor blade. The rotor blade includes a sidewall that extends between a root portion and a tip portion. The rotor blade monitoring system includes a fiber optic strand that is coupled to the rotor blade sidewall. The fiber optic strand has a length that extends from the root portion towards the tip portion. A plurality of sensors are coupled to the fiber optic strand. Each sensor of the plurality of sensors is axially spaced along the fiber optic strand and is configured to transmit a signal indicative of a position of a respective portion of the rotor blade.

Abstract: A bridge intelligent cable system with a built-in fiber grating sensor is provided, which is applied in a cable bearing structure such as a cable-stayed bridge, a suspension bridge, and an arch bridge. The system includes an anchor cup, a wire dividing plate, a connecting cylinder, a fiber grating sensor, and a cable body, in which the fiber grating sensor includes a fiber grating strain sensor and a fiber grating temperature sensor, tail fibers of the fiber grating strain sensor and the fiber grating temperature sensor are led out, the packaged fiber grating strain sensor is fixedly connected to an outer-layer steel wire of the connecting cylinder, the packaged fiber grating temperature sensor is suspended on the steel wire of the connecting cylinder, holes are punched in the wire dividing plate, and a preserved steel pipe is buried in advance in the connecting cylinder and the anchor cup.

Abstract: A method, apparatus and system for determine a parameter of a structure is disclosed. A fiber optic cable is coupled to a member. The fiber optic cable includes at least a first core helically arranged in the fiber optic cable that includes at least a first sensor and a second sensor. A first measurement related to the parameter is obtained at the first sensor, and a second measurement at the second sensor related to the parameter is obtained at the second sensor. A difference between the first and second measurements is used to determine the parameter.

Abstract: A non-linear strain gage includes a target for association with an object for which at least one of strain and fatigue damage is to be measured, a sensor, and a computer. The target incorporates a nested binary code symbol for perimeter-based deformation and strain analysis and emits a detectable physical quantity. The binary code symbol includes a boundary binary code symbol having a perimeter constructed of line segments and at least a core code symbol that provides encoded data. The core code symbol is nested within and concentric with the boundary binary code symbol. A method of measuring strain on an object directly using the non-linear strain gage is also provided.

Abstract: 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.

Abstract: An instrument system that includes an elongate body in a geometric configuration, an optical fiber, and a controller is provided. The optical fiber is operatively coupled to the elongate body and has a strain sensor provided on the optical fiber, wherein at least a portion of the optical fiber is in the geometric configuration. The controller is operatively coupled to the optical fiber and adapted to receive, from a source other than the optical fiber, information indicative of the geometric configuration, receive a signal from the strain sensor, and associate the signal with the geometric configuration.

Abstract: The invention relates to an optical strain gauge using a glass fiber (1) comprising a Bragg grating (2). The glass fiber is coated with a sheath (3) of polyether ether ketone with an admixture of at least 10 weight percent and a maximum of 40 weight percent of an inorganic filler, with a particle size of between 0.08 ?m and 12 ?m. The outer diameter of the sheath (3) is between 0.2 mm and 1.2 mm. The ratio D/d between the outer diameter D of the sheath (3) and the diameter d of the glass fiber (1) is between 2 and 6. A pressure of the sheath (3) on the glass fiber (1) is such that essentially no relative movement can occur between the glass fiber (1) and the sheath (3).

Abstract: An interferometric measurement system measures a parameter using at least one optical waveguide. A memory stores reference interferometric pattern data associated with a segment of the optical waveguide. Interferometric detection circuitry detects and stores measurement interferometric pattern data associated with the segment of the optical waveguide during a measurement operation. A spectral range of the reference interferometric pattern of the optical waveguide is greater than a spectral range of the measurement interferometric pattern of the optical waveguide. A processor shifts one or both of the measurement interferometric pattern data and the reference interferometric pattern data relative to the other to obtain a match and to use the match to measure the parameter. An example parameter is strain.

Abstract: A sensor, sensor assembly and a method of sensing, in which the sensor is in contact with a material or structure and the sensor directly measures one or more property changes in the material by means of light reflection and scattering using a reflective target.

Abstract: An instrument system that includes an elongate body and an optical fiber is provided. The elongate body includes a first elongate portion having a hollow lumen and a second elongate portion adjacent to the first elongate portion. The optical fiber is located in the lumen of the first elongate portion and in the second elongate portion. The optical fiber has a strain sensor provided thereon. The lumen is adapted to allow the optical fiber to move in the lumen relative to the elongate body, and the second elongate portion is adapted to prohibit all movement of the optical fiber relative to the elongate body.

Abstract: Nanowire array structures based on periodic or aperiodic nanowires are provided in various configurations for sensing and interacting with light and substances to provide various functions such as sensors for detecting DNAs and others and solar cells for converting light into electricity.

Abstract: Testing method for determining the distribution of a physical property along a wind turbine blade comprising the following steps: a) installing inside the blade a first optical fibre cable (13) along the leading and trailing edges and a second and third centered optical fibre cables (14, 15) at both sides of the blade (9), leaving in them a free end; b) applying one load to the blade (9) in a test bench (10) placed at the blade factory; c) obtaining the strain distribution produced by said load along the blade (9) using a suitable external equipment connected to said free end for measuring the strain using Rayleigh scattered light; d) determining the distribution of said physical property from said strain distribution; e) comparing the distribution of said physical property with its design distribution. The invention also comprises a method of installation of said cables.