The invention is concerned with a structured optical fibre sensor, comprising a light source (1), a detection system (2) and a Bragg grating optical fibre (3) connected to said source and said system. The light source is a wavelength-tunable laser emission device (1) comprising a cavity (CA) delimited by a first and a second Sagnac mirror (M1, M2). The cavity comprises an amplifying medium (AM) and a tunable spectral filter using the Vernier effect (F), said filter (F) comprising at least three resonant rings (R.sub.1, R.sub.2, R.sub.N−1, R.sub.N) arranged in cascade, each resonant ring integrating a wavelength-tunable reflectivity loop mirror (MBR).

The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

A system for interrogating an interferometer. The system comprises an optical signals generation system for concurrently generating a plurality of optical signals that each have a modulation parameter that the other of the plurality of optical signals do not have. The optical signals generation system is for optically coupling each of the plurality of optical signals to a plurality of optical ports of the interferometer for ingress of the plurality of optical signals into the interferometer. The system comprises an interferometer output processing system. Also disclosed herein is an interferometric system and a method for interrogating an interferometer.

The invention is concerned with a structured optical fibre sensor, comprising a light source (1), a detection system (2) and a Bragg grating optical fibre (3) connected to said source and said system. The light source is a wavelength-tunable laser emission device (1) comprising a cavity (CA) delimited by a first and a second Sagnac mirror (M1, M2). The cavity comprises an amplifying medium (AM) and a tunable spectral filter using the Vernier effect (F), said filter (F) comprising at least three resonant rings (R.sub.1, R.sub.2, R.sub.N−1, R.sub.N) arranged in cascade, each resonant ring integrating a wavelength-tunable reflectivity loop mirror (MBR).

A method and system of compensating for body deformation during image acquisition or external beam treatment includes acquiring image data of a body and peak wavelength data from a plurality of fiber Bragg gratings (FBGs) disposed on the body aligned along a predetermined coordinate system on the body, such as a cartesian coordinate system. The method further comprises detecting effective shifts of the Bragg wavelengths of the FBGs caused by body deformation during image acquisition, and controlling the movement of the body through a cavity in a scanning device and controlling the acquisition of the image data or external beam treatment during body deformation based on the effective shifts of the Bragg wavelengths of the FBGs.

A garment for real time detection of body deformation during an image scan includes a front portion, made of a compression material and having a plurality of fiber Bragg gratings (FBGs). The garment includes a plurality of light emitters, each light emitter configured to pulse light waves through a corresponding FBGs and a plurality of light sensors, each light sensor attached to a corresponding FBG and configured to receive pulsed light waves. A processor obtains data through a data acquisition module configured to receive from the light sensors peak wavelengths reflected by the FBG Based on the effective shifts of the Bragg wavelengths of the FBGs aligned along the cartesian coordinate system, the processor may correct acquired image data or re-direct an external beam treatment to compensate for body deformation during an image scan.

A garment for real time detection of body deformation during an image scan includes a front portion, made of a compression material and having a plurality of fiber Bragg gratings (FBGs). The garment includes a plurality of light emitters, each light emitter configured to pulse light waves through a corresponding FBGs and a plurality of light sensors, each light sensor attached to a corresponding FBG and configured to receive pulsed light waves. A processor obtains data through a data acquisition module configured to receive from the light sensors peak wavelengths reflected by the FBG Based on the effective shifts of the Bragg wavelengths of the FBGs aligned along the cartesian coordinate system, the processor may correct acquired image data or re-direct an external beam treatment to compensate for body deformation during an image scan.

Systems and methods for sensing changes in an optical sensing fibre, principally for detecting changes in strain. A plurality of optical probe pulses at different optical frequencies (f.sub.1, f.sub.2, . . . f.sub.n) spaced by f are transmitted into the sensing fibre. Light backscattered from the optical sensing fibre may be mixed with delayed backscatter frequency shifted by f+f.sub.m where f.sub.m is a heterodyne frequency. The backscattered or mixed light may be detected to determine changes in the sensing fibre. f may be chosen to optimise performance.

An EHz ultrafast modulated pulse scanning laser and a distributed fiber sensing system. A plurality of phase-shift gratings are engraved on a doped fiber, the phase-shift gratings having different central window wavelengths and a wavelength interval between the adjacent central window wavelengths being a preset fixed value. When a pump light emitted by a pump laser source is coupled by a wavelength division multiplexer and enters the doped fiber, a single-mode narrow-linewidth laser light having multiple wavelengths with a wavelength interval being a preset fixed value can be generated, by using the phase-shift gratings graved on the doped fiber. The ultrafast modulation is completed by using a time-domain control method based on an EOM. An internally frequency converted pulse light formed by splicing pulse lights whose frequencies linearly increase is obtained, thus forming the EHz ultrafast modulation of a distributed feedback fiber laser. In this way, a coherence length of an output laser light is increased while a frequency of the laser light is remained.