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 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.

In order to enable an area suspected of having a communication abnormality to be identified from among a communication device and a communication path that constitute a communication system, this abnormality identification device is provided with: a first output unit which outputs first information that is information indicating the suitability of a transmission signal to be supplied to a communication channel; a second output unit which outputs second information that is information indicating the suitability of a reception signal corresponding to the transmission signal that has arrived via the communication channel; and a third output unit which outputs third information that is information indicating the suitability of a signal obtained by applying predetermined processing to the reception signal.

An in-line fiber-optic sensing element, a system, and methods for detecting strain using a fiber optic sensor are described that include using at least two chirped grating structures. In an implementation, an in-line fiber-optic sensing element that employs example techniques in accordance with the present disclosure includes an optically transmissive fiber including a core and an outer layer; a Fabry-Perot cavity defined by a portion of the optically transmissive fiber and two chirped fiber-Bragg grating structures, where the two chirped grating structures are separated and are configured to reflect light.

Object is to enable a directly-modulated semiconductor laser to be applied as a light source of probe light. A transmission unit configured to generate probe light; and a reception unit including a receiver-side optical bandpass filter that extracts a Stokes component of Brillouin backscattered light from backscattered light which is caused by the probe light in a measurement target optical fiber, and a self-delayed heterodyne interferometer that detects a change in a frequency shift amount of the Stokes component as a phase difference are included. The transmission unit includes a directly-modulated light source configured to generate an optical pulse, and a transmitter-side optical bandpass filter provided in a stage following the directly-modulated light source, and configured to transmit wavelength of an ON level of the optical pulse as the probe light, and block wavelength of an OFF level.

A method of improving measurement speed of distributed optical fiber sensors by adopting orthogonal signals and the system thereof is disclosed, which is related to the optical fiber sensor field and solves the problems that conventional technology will increasing the bandwidth of the received signal, reducing the signal-to-noise ratio of the received signal or distortion the spatial resolution of the system. The method comprises steps of generating N periodic orthogonal optical pulse sequence; injecting the N periodic orthogonal optical pulse sequence into the optical fiber under test(5); collecting the scattered light signal; demodulating the scattered light signal with the local oscillating light and then converting into digital signals; extracting the scatter information of the orthogonal optical pulses from the collected digital signals; and arranging the scattered information in order of precedence of the infusion. The measurement speed of the distributed optical fiber sensors is improved by N1 times.

A fiber acoustic emission sensing apparatus and method including a laying device and an acoustic emission source; the laying device comprises base plate, first side plate and second side plate, the top portion of the first side plate connected with the top portion of the second side plate through an arc-shaped fiber-carrying channel, a main cavity formed by the first side plate and the second side plate; top portions of the first and second side plates respectively hinged with first and second arc-shaped covers, the lower end surface of the first arc-shaped cover fixedly connected with a first arc-shaped pressing body, the lower end surface of the second arc-shaped cover fixedly provided with a second arc-shaped pressing body, a first sensing fiber arranged under the first arc-shaped pressing body, and a second sensing fiber arranged under the second arc-shaped pressing body.

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.

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.