Abstract: Provided is a spectral sensor array, including: a planar waveguide on a substrate; a chirped input coupling grating, wherein the chirped input coupling grating comprises a transverse chirp to provide a spectrally selective coupling of incident light into the planar waveguide; an output coupling grating; and an array of photodetectors arranged to receive the light coupled out of the waveguide.

Abstract: Described are methods and systems using optical fiber interferometry to sense interference causing events in a region of interest and differentiate between a strain event and a thermal event. Other methods and systems relate to the use of optical fiber interferometry for determining temperature offset in a region of interest and using the determined temperature offset for determining temperature in the region of interest.

Abstract: A fibre optic sensing device is provided. The fibre optic sensing device includes a plurality of optical fibre portions, wherein each optical fibre portion is arranged to receive laser light from a common laser and reflect the laser light to a common detector. Each optical fibre portion includes a first reflector spaced from a distal end of the optical fibre portion and a second reflector at the distal end. Each optical fibre portion also includes a sensor provided at the distal end of the optical fibre portion. The sensor includes a third reflector the position of which varies depending on a value of a property being sensed. A distance between the first and second reflectors is different for each of the optical fibre portions.

Abstract: A photon source includes a bus waveguide, a photon source pump laser coupled to the bus waveguide and a plurality of optical resonators coupled to the bus waveguide. Each optical resonator of the plurality of optical resonators has a respective resonance line width and a respective resonance frequency, wherein a bandwidth of the resonant center frequencies of the plurality of optical resonators is greater than a bandwidth of the photon source pump laser. The bus waveguide produces photons in response to receiving laser pulses from the pump laser.

Abstract: An apparatus, and related method, relates generally to a fiber-optic sensing system. In such a system, fiber-optic sensors are in a rosette or rosette-like pattern. An optical circulator is coupled to receive a light signal from a broadband light source, to provide the light signal to the fiber-optic sensors, and to receive a returned optical signal from the fiber-optic sensors. A spectral engine is coupled to the optical circulator to receive the returned optical signal and configured to provide an output signal.

Abstract: A side illuminated multi point multi parameter optical fiber sensor that requires no sensitive coating is provided. This sensor comprises an optical fiber having at least one removed cladding section as the sensitive region, at least one probing light source that side illuminates the fiber, a power supply, a detector, a signal processor and a display. The sensitive optical fiber is optically affected by the presence of a measurand medium that can fluoresce, phosphoresce, absorb and/or scatter the probing light. This probing light is guided by the fiber core towards a detector which measures the light intensity and this light intensity is correlated with a measurand.

Abstract: A force sensing device comprises: a membrane (120), which is configured to deform upon receiving a force; a first Mach Zehnder-type interferometer device (110); a second Mach Zehnder-type interferometer device (130), wherein a first measurement propagation path (114) of the first Mach Zehnder-type interferometer device (110) and a second measurement propagation path (134) of the second Mach Zehnder-type interferometer device (130) are arranged on or in the membrane (120), and wherein the first measurement propagation path (114) and the second measurement propagation path (134) are differently sensitive to applied force on the membrane (120).

Abstract: An integrated seismic system and method for monitoring seismic parameters of a subsurface structure is provided. The integrated seismic system includes a base station; a plurality of mobile satellite nodes, each of the plurality of mobile satellite nodes having sensor stations for collecting seismic data from the subsurface structure; and a fiber optic cable extending from the base station to the plurality of mobile satellite nodes and operatively linking the plurality of mobile satellite nodes and the sensor stations; the base station comprising: a light source for sending a light through the fiber optic cable, the light being distributed to the sensor stations and, in the sensor stations, experiencing a change or phase shift related to a physical property being measured; and a seismic acquisition unit for receiving seismic signals from the plurality of mobile satellite nodes via the fiber optic cable and generating seismic parameters therefrom.

Abstract: An optical system can lock a wavelength of a tunable laser to a specified wavelength of a temperature-insensitive spectral profile of a spectral filter. In some examples, the spectral filter, such as a Fabry-Perot filter, can have a temperature-insensitive peak wavelength and increasing attenuation at wavelengths away from the peak wavelength. The spectral filter can spectrally filter the laser light to form filtered laser light. A detector can detect at least a fraction of the filtered laser light. Circuitry coupled to the detector and the laser can tune the tunable laser to set a signal from the detector to a specified value corresponding to a specified wavelength in the spectral profile, and thereby adjust the selectable wavelength of the tunable laser to match the specified wavelength. In some examples, the optical system can include a polarization rotator, and can use polarization to separate incident light from return light.

Abstract: An optical network including an input to receive from an optical network light comprising plural wavelength components. An optical wavelength selective filter, optically connected to the input, extracts a first wavelength component of the plural wavelength components from the light, thereby providing a first optical signal including the first wavelength component and a second optical signal including a remainder of the plural wavelength components a light emitter to provide a modulated broadband optical signal. A first output, optically connected to the optical wavelength selective filter, receives a first portion of the second optical signal for transmission to a light detector and a second output, optically connected to optical wavelength selective filter, receives a second portion of the second optical signal for transmission to the optical network.

Abstract: Fiber optic sensors are used to monitor the integrity of a subsurface concrete structure such as a pile or diaphragm wall. A fiber optic sensor array (48) is attached to a reinforcement or framework assembly (20) for the subsurface concrete structure. Concrete is applied to surround the reinforcement or framework assembly (20) and fiber optic sensor array (48). The fiber optic sensor array (48) is then used to collect temperature data during hydration of the subsurface concrete structure. The temperature data is monitored in real time to determine differentials across the structure, indicative of a problem within the structure.

Abstract: At least one fiber-optic sensor unit measures a mechanical variable which affects a rail having a certain length and a neutral axis that extends along said length of the rail. The at least one fiber-optic sensor unit is disposed at an angle of 30° to 60°, in particular 45°, relative to the neutral axis or at an angle of ?30° to ?60°, in particular ?45°, relative to the neutral axis. The at least one fiber-optic sensor unit is irradiated with primary light in order to generate a signaling light in a reflection mode or transmission mode. The intensity of the signaling light is sensed. The signaling light is evaluated.

Abstract: Methods, systems, devices, and products for acoustic detection in a borehole.

Abstract: A composite material packaged fiber grating sensor and a manufacturing method thereof. The sensor includes a fiber grating sensor component, a composite material coverage layer, a resin package layer and a composite material substrate layer. In the sensor, a temperature fiber grating and a strain fiber grating are packaged in a composite material structure, so that the structure is light and simple, its computability with the composite material is good, the measurement accuracy is high, and the survival rate and the service life of the installed sensor can be greatly improved, the sensor component can be externally pasted on to or inter-implanted in a composite material structural part, and can be applied to the distributed online health monitoring on the structural part. The manufacturing method of the composite material packaged fiber grating sensor is simple, efficient and stable, and is suitable for rapid mass production by enterprises.

Abstract: The present disclosure relates to a substrate unit of a nanostructure assembly type, an optical image apparatus including the same, and a controlling method thereof, and the substrate unit of the nanostructure assembly type according to an exemplary embodiment includes: a lower substrate; an upper substrate separated from the lower substrate, an observation object being able to be positioned at the upper substrate; and at least one metal nanostructure positioned on the lower substrate, wherein the at least one metal nanostructure is capable of being assembled on the lower substrate or separated from the lower substrate.

Abstract: A communication apparatus for a fiber-optic communication system for an aircraft that includes: an optical coupler; an input port optically coupled to the optical coupler via a first waveguide, the input port arranged to receive light; a modulator optically coupled to the optical coupler via a second waveguide, the modulator having a logic input and a fiber having a fiber Bragg grating (FBG) receiving light from the input port via the optical coupler, the modulator operable to vary a strain force applied to the fiber according to a logic signal received at the logic input to modulate a wavelength of a modulated light signal reflected by the FBG back to the optical coupler; and an output port optically coupled to the optical coupler via a third waveguide to receive the modulated light signal therefrom, the output port being operable to output the modulated light signal.

Abstract: Described are methods and systems using optical fiber interferometry to sense interference causing events in a region of interest and differentiate between a strain event and a thermal event. Other methods and systems relate to the use of optical fiber interferometry for determining temperature offset in a region of interest and using the determined temperature offset for determining temperature in the region of interest.

Abstract: The invention relates to a method for digitally processing a signal from an optoelectronic distributed measuring device based on Brillouin scattering, said device comprising a continuous light source (1), a coupler (2), an acousto-optic modulator (3), an optical fiber (5) to be tested so that it emits in return a signal by spontaneous Brillouin backscattering at a frequency ?F equal to ?p??Bz, where ?Bz is the Brillouin frequency to be measured at every point z of said optical fiber (5), a local oscillator (16) emitting another light signal intended to be mixed with said return signal emitted by Brillouin backscattering by said optical fiber (5) to be tested, a detection module (9) able to detect said Brillouin shift frequency ?Bz at every point z of said optical fiber and a processing module for linking this Brillouin shift frequency ?Bz at every point z of said optical fiber to a temperature value and a strain value.

Abstract: Embodiments of the present disclosure provide a monitoring apparatus for an optical signal to noise ratio, a signal transmission apparatus and a receiver. White noise power of received signals is calculated according to noise power and power of pilot signals of the received signals in different polarization states, and influence of a nonlinear noise is excluded, thereby accurately estimating an optical signal to noise ratio, for example, with a calculation process being simple and an application range being relatively wide.

Abstract: A fiber Bragg grating interrogator assembly, comprising: an optical fiber including a fiber Bragg grating (FBG; 122) having a variable Bragg wavelength (?B) and a dynamic range of interest (??dyn,B) over which the Bragg wavelength (?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 (??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.

Abstract: Optical communication systems include optical time domain reflectometers that are coupled to link fibers to determine link fiber lengths. After length measurement, chromatic dispersion associated with the measured length is estimated. In some examples, the estimated chromatic dispersion is compensated. A single OTDR can be used to assess a pair of link fibers coupling first and second network nodes by injecting a probe pulse at a common end of the link fibers or by routing the probe pulses from a remote end of one link fiber into a remote end of a second fiber.

Abstract: A system for transmission of optical data signals has first optical processing circuitry for receiving a plurality of digital signals and applying at least one of a Hermite-Gaussian function, a Laguerre-Gaussian function or an Ince-Gaussian function to each of the received plurality of digital signals. The first optical processing circuitry also combines each of the at least one of the Hermite-Gaussian function, the Laguerre-Gaussian function or the Ince-Gaussian function applied plurality of digital signals into a single carrier signal. An optical transmitter transmits the single carrier signal. An optical receiver receives the transmitted single carrier signal.

Abstract: A position encoder apparatus, including a scale having a series of position features; and a readhead configured to read the series of position features via a snapshot capture process. The snapshot capture process is adaptable so as to compensate for the relative speed between the scale and readhead.

Abstract: A method of providing optical supercontinuum pulses can comprise generating optical pump pulses with an optical pump laser, the optical pump pulses having a pump pulse repetition rate; launching optical pump pulses into a nonlinear optical element comprising an optical fiber; generating optical supercontinuum pulses from the optical pump pules via spectral broadening within the optical fiber; selectively providing a plurality of different repetition rates for the optical pump pulses so as to generate optical supercontinuum pulses having different repetition rates; and providing nominally identical spectral broadening of the optical supercontinuum pules having the different repetition rates.

Abstract: A high sensitivity structural health monitoring network includes a plurality of sensor nodes disposed apart from each other and communicating through one or more sensor channels. The nodes include smart sensor circuit boards with an interface to a wireless smart sensor board platform, a multi-axis accelerometer having a measurement range and resolution set to provide sensitivity to measure ambient structural vibrations an analog to digital converter for converting signals that includes a plurality of individual channels being individually programmable for signal conditioning for providing data to the interface. A network framework provides network services including a time synchronization service with network-wide global timestamps for sensor data and a unified sensing service that supports collection of data for all sensor channels from all nodes together with a single set of associated time stamps.

Abstract: A high precision fiber-optic device and method are developed for measuring a temperature profile in a long length area. The temperature profile is derived based on a ratio between the intensities of anti-Stokes Raman and Stokes Raman backscattered components. The power output of the amplified pulsed optical radiation delivered to the sensing optical fiber via a reference optical fiber, is controlled such as to maintain a substantially fixed intensity level of the anti-Stokes Raman component of the optical radiation back scattered from the reference optical fiber. Controlling the output power of the of the amplified pulsed optical radiation is carried out based on a feedback representative of the intensity level of the anti-Stokes Raman component of the optical radiation back scattered from the reference optical fiber.

Abstract: The present disclosure provides a novel fiber optic sensing device using ultra-weak, terahertz-range reflector structures. A fiber optic sensor device for distributed measurements (strain/temperature) includes an optical fiber detection arm having an inner core extending along a length of the optical fiber, an outer cladding surrounding the inner core, and at least one ultra-weak, terahertz-range reflector structure. Each reflector structure is comprised of two or more ultra-weak range reflectors (gratings) written at a spacing corresponding to the terahertz range and formed along a length of the inner core of the optical fiber. A narrow bandwidth, tunable laser interrogation system interrogates the optical fiber and measures changes in reflections and interference patterns caused by physical changes in the optical fiber.

Abstract: A level sensor assembly includes a fiber that is configured to be at least partially disposed in a tank and to be coupled to a light source and to a light detector. The fiber includes a plurality of sensing regions spaced apart along a length of the fiber. Each sensing region of the plurality of sensing regions includes a Bragg grating configured to generate a reflection spectrum responsive to incident light and a strain layer around the Bragg grating. Each strain layer is configured to induce a strain on the fiber at a respective Bragg grating based on a temperature of the strain layer such that shifts in the reflection spectra of the Bragg gratings indicate which of the sensing regions are submerged in a liquid.

Abstract: The application describes methods and apparatus for distributed fiber sensing, especially distributed acoustic/strain sensing. The method involves launching interrogating radiation in to an optical fiber and sampling radiation backscattered from within said fiber at a rate so as to acquire a plurality of samples corresponding to each sensing portion of interest. The plurality of samples are divided into separate processing channels and processed to determine a phase value for that channel. A quality metric is then applied to the processed phase data and the data combined to provide an overall phase value for the sensing portion based on the quality metric. The quality metric may be a measure of the degree of similarity of the processed data from the channels. The interrogating radiation may comprise two relatively narrow pulses separated by a relatively wide gap and the sampling rate may be set such that a plurality of substantially independent diversity samples are acquired.

Abstract: Device for spatially resolved measurement of temperature, strain, or both by Brillouin scattering, with a laser light source (1) for generating a laser radiation, an optical fiber (5) used for the measurement, into which the laser radiation can be coupled in and from which Brillouin signals generated by Brillouin scattering can be coupled out, sensors for detecting the coupled-out Brillouin signals, evaluators for determining spatially resolved from the detected Brillouin signals the temperature, strain, or both of sections of the optical fiber (5), a polarization beam splitter (10, 11) capable of splitting the coupled-out Brillouin—signals into two components (12, 13) having mutually different polarizations, and an optical coupler (16, 17) for admixing a laser radiation to the Brillouin signal.

Abstract: Embodiments of the present disclosure provide a monitoring apparatus for an optical signal to noise ratio, a signal transmission apparatus and a receiver. The monitoring apparatus includes a selecting unit configured to select a time domain, and/or frequency domain range for calculating noise power of received signals according to a location of a pilot signal in the received signals in a time domain and/or frequency domain, and a calculating unit configured to calculate the noise power of the received signals according to the received signals in the selected range of the time domain and/or frequency domain, and calculate an optical signal to noise ratio of the received signals according to the noise power. The optical signal to noise ratio may be accurately estimated, with a process of calculation being simple and a scope of application being relatively wide.

Abstract: A sensor system for a laminated structure may include a sensor assembly disposed between a first layer and a second layer of the laminated structure. The sensor assembly may include a first anchor member and a second anchor member spaced at a predetermined distance from one another. A sensor chamber is formed between the first and second anchor members. The sensor assembly may also include a sensing line extending through the anchor members and the sensor chamber. The sensing line may include a configuration within the sensor chamber for sensing one of stress forces within the laminated structure, temperature or temperature changes within the laminated structure. A first transport tube may extend from the first anchor member opposite the sensor chamber and a second transport tube may extend from the second anchor member opposite the sensor chamber. The sensing line extends through the first and second transport tubes.

Abstract: An optical monitoring device for monitoring curvature along a flexible medical instrument including optical fibers, a light source to inject light into the optical fibers, a light receiver configured to measure an optical characteristic of reflected light from the optical fibers, a processor to analyze the measured optical characteristic to determine a curvature of the optical fibers, compare the curvature with a threshold curvature, determine a location along the optical fibers of the determined curvature, store previous curvatures and their associated location along the fibers in a storage, analyze the stored curvatures by counting or summing curvatures determined at a given location over time to predict breakdown of the flexible medical instrument, and produce an indication when the stored curvatures determined at the given location over time predict breakdown of the flexible medical instrument at the given location.

Abstract: A thermometer includes a substrate; an optical resonator disposed on the substrate and including an optical resonance, the optical resonator being configured to receive a resonant frequency corresponding to the optical resonance; and a waveguide disposed on the substrate proximate to the optical resonator to receive input light, to communicate the resonant frequency to the optical resonator, and to transmit output light; wherein an aperture is interposed between: the substrate and the optical resonator, the substrate and the waveguide, or a combination comprising at least one of the foregoing, and the thermometer is configured to change the optical resonance in response to a change in temperature of the optical resonator.

Abstract: Optic fiber sensor characterized in that the sensing fiber is provided with a continuous Bragg grating covering the entire fiber length which is dedicated to sensing and along which spatially resolved measurements are performed.

Abstract: A system for measuring strain includes an optical fiber having a central portion secured between two fixed points. A first light source outputs light at a first frequency and a second light source outputs light at a second different frequency. The two light sources are both coupled to a first end of the optical fiber. A back scatter detector is also coupled to the first end to receive a return light signal from the optical fiber and outputs a signal based thereon. A forward scatter detector is coupled to a second end of the optical fiber to receive a forward light signal from the optical fiber and outputs a signal based thereon. A processor receives the signals from the back scatter detector and the forward scatter detector and generates an output signal proportional to the strain between the two fixed points based on the received signals.

Abstract: The invention relates to methods and apparatus of measuring real time temperature conditions within a reformer. The data is then used for process control optimization, overheat protection, and improved creep damage and fatigue life prediction.

Abstract: A system for monitoring a physical change of a marine structure includes a complex optical measuring instrument configured to detect a behavior and structural change of the marine structure by using at least one optical sensor by means of optical fiber Bragg grating.

Abstract: The present invention relates to a method for compensation, for example, for temperature compensation of a fiber optic measurement system designed for determining a mechanical quantity. First and second fiber Bragg gratings have a respective Bragg wavelength, wherein the fiber Bragg gratings are irradiated with primary light. After applying a mechanical quantity to the first and second fiber Bragg gratings, the Bragg wavelengths of the fiber Bragg gratings are changed by the mechanical quantity.

Abstract: A high sensitivity structural health monitoring network includes a plurality of sensor nodes disposed apart from each other and communicating through one or more sensor channels. The nodes include smart sensor circuit boards with an interface to a wireless smart sensor board platform, a multi-axis accelerometer having a measurement range and resolution set to provide sensitivity to measure ambient structural vibrations an analog to digital converter for converting signals that includes a plurality of individual channels being individually programmable for signal conditioning for providing data to the interface. A network framework provides network services including a time synchronization service with network-wide global timestamps for sensor data and a unified sensing service that supports collection of data for all sensor channels from all nodes together with a single set of associated time stamps.

Abstract: A method for detecting a non-superconducting transition of a superconducting wire including a substrate, a superconducting layer having a critical temperature of 77 K or more, and a metal stabilization layer includes, adhesively attaching an optical fiber where a plurality of fiber Bragg gratings are formed in a core along a longitudinal direction thereof to the superconducting wire; measuring in advance a Bragg wavelength shift of the fiber Bragg gratings for a temperature variation of the superconducting wire, and determining a relational expression based on the shift for a temperature calculation of the superconducting wire; determining temperature variations of the fiber Bragg gratings before and after the non-superconducting transition of the superconducting wire using the relational expression; and calculating a propagation rate of the non-superconducting transition based on both a time difference of temperature increases of the fiber Bragg gratings, and an interval between each of the fiber Bragg grati

Abstract: A sensor system for measuring an operating parameter of a wind turbine component is described. The fiber optic sensor system comprises a light source for outputting light in a predetermined range of wavelengths, and an optical fiber comprising a long Fiber Bragg Grating, extending continuously over a length of the optical fiber to provide a continuous measurement region in the optical fiber. The optical fiber 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 fiber, 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: The present invention relates to an optical sensing system (1) for determining the position and/or shape of an associated object (O), the system comprises an optical fibers (10) having one or more optical fiber cores (9) with one or more fiber Bragg gratings (FBG, 8) extending along the full length where the position and/or shape is be to determined of said object (O). A reflectometer (REFL, 12) measures strain at a number of sampling points along the optical fiber cores, and a processor (PROC, 14) determines the position and/or shape based on said measured strains from the plurality of optical fiber cores. The fiber Bragg grating(s) (FBG, 8) extends along the full length of said optical fiber cores (9), the fiber core having a spatially modulated reflection (r) along the said full length of the optical fiber core so that the corresponding reflection spectrum is detectable in said wavelength scan.

Abstract: A fiber grating sensor system is used to measure key parameters that include pressure, strain and temperature at specific locations and at high speed. The system relies on spectral properties associated with the fiber grating sensors, the light source and the optical detection system to provide these capabilities. The system has been successfully applied to measurement of pressures up to 1,200,000 psi and by increasing the spectral width of the light source extensions of pressure measurements to 4,000,000 psi and higher are possible. Temperature change measurements have been made of 400 degrees C. over a period of 25 micro-seconds limited by the physical response of the fiber sensors and the output detector bandwidth both of which can be greatly improved by reducing fiber sizes and with improved detectors. Novel methods have been devised to lower cost and enable measurements with spatial location, speed and accuracy that have been very difficult or not yet achieved.

Abstract: A spectroscopic measurement system, which may utilize multiple plasmonic filters associated with a cuvette to monitor different wavelengths of light. The spectroscopic measurement system may measure absorbance and or fluorescence, and may have built-in low cost CMOS image sensor(s). Reagents and samples may be introduced to the cuvette from a fluidics manifold. Multiple sets of combined cuvettes, image sensors and plasmonic filters may utilize a single fluidics manifold for reagent and sample distribution.

Abstract: A method for the adjustment of an optical measurement system comprises providing an optical measurement system, which comprises, as optical elements, a beam splitter; a first photo sensor, exposed by a first partial beam from the beam splitter; an optical filter; a second photo sensor, arranged downstream of the optical filter, exposed by a second partial beam from the beam splitter. Additionally, the angularity and relative position between multiple optical elements is designed to be adjustable.

Abstract: A fiber Bragg grating (FBG) interrogation method allows for high frequency dynamic measurement. The method may utilize a broad band light source connected to the sensing elements. Each sensing element may comprise two wavelength matching FBGs, a coupler, and a photodiode. The FBG closest to the light source may attenuate the central wavelength in the transmission spectrum and thus the reflection spectrum of the second FBG. Variations in intensity of the second FBG may be measured by the photodiode and can be calibrated to the desired measurands.

Abstract: A system comprises a source of entangled photon pairs. The source is to place a signal photon and an idler photon in individual unknown quantum states but in a known entangled quantum state. One or more transmission channels are connected to the source. Each of the one or more transmission channels transmits one of the signal photon or the idler photon. Each of the one or more transmission channels is to substantially balance an instantaneous transmission loss with an instantaneous transmission gain distributed over a transmission distance. Analysis interferometers are configured to receive a corresponding one of the signal photon or the idler photon. Each of the one or more analysis interferometers is to perform a basis measurement on one of the signal photon or the idler photon. Single-photon detectors detect one of the signal photon or the idler photon.

Abstract: Apparatus and techniques for measuring seismic parameters, such as ground force, of a seismic vibrator used for generating seismic signals through a geological formation are provided. The seismic vibrator has a base plate positionable adjacent a ground surface of the geological formation. A sensor pad may be provided with an optical cable positionable between the base plate of the seismic vibrator and the ground surface of the geological formation, a laser for passing a light through the optical cable, and a detector for detecting disturbances in the laser light whereby a ground force applied to the ground surface may be determined.

Abstract: Optical pulses are output from a light source to an optical fiber at one selected emission wavelength, a reflection light reflected at a fiber Bragg grating at the optical fiber is received at an optical receiver and is converted to a reflection signal by an optical to electrical conversion, a fiber Bragg grating which reflects the reflection light is identified by the signal processing unit when an intensity of the reflection signal obtained by the optical receiver is over a predetermined threshold value, and a measurement step that calculates acoustic frequencies at the fiber Bragg grating based on a temporal change of the intensity of the reflection signal at the fiber Bragg grating is repeated more than two times while changing an emission wavelength of the light source. The acoustic frequency at each fiber Bragg grating is calculated to determine an acoustic distribution along a longitudinal direction of the fiber.