This invention relates to a force and moment balance (1) including a support (9) therefor and more specifically, but not exclusively, to a force and moment balance (1) and a support (9) therefor for a wind tunnel. Force and moment balances are known in the art and are typically used in wind tunnels to measure the force and moment loads on a model in the wind tunnel. A problem with current balances is that there is inherent vertical movement associated with horizontal force. According to the invention, the balance (1) has a fixed end (3) and a movable end (6) with a number of supports (9) between the fixed end (3) and the movable end (6). Each support (9) includes compensation means to compensate for resultant movements caused by lateral movement of the movable end (6) relative to the fixed end (3).

A sensor system includes a radiation source, an optical fiber, and a detection device. The radiation source is arranged to emit pulses of radiation. The optical fiber comprises a first end and a core. The first end is arranged to receive pulses of radiation output from the radiation source such that, in use, the pulses of radiation are coupled into the fiber. The core is arranged to support propagation of the pulses of radiation along the fiber. The core includes a plurality of reflectors each comprising a portion of the core having a refractive index which is different to the refractive index of adjacent regions of the core. Reflections of a pulse of radiation from adjacent reflectors output at the first end of the fiber are resolvable from each other in the time domain. The detection device is arranged to measure radiation output from the first end of the fiber and resolve radiation reflected at different locations in the core of the fiber.

A fiber optic transducer is provided. The fiber optic transducer includes a fixed portion configured to be secured to a body of interest, a moveable portion having a range of motion with respect to the fixed portion, a spring positioned between the fixed portion and the moveable portion, and a length of fiber wound between the fixed portion and the moveable portion. The length of fiber spans the spring. The fiber optic transducer also includes a mass engaged with the moveable portion. In one disclosed aspect of the transducer, the mass envelopes the moveable portion.

A method for estimating a parameter includes: generating an optical signal, the optical signal modulated via a modulation signal; transmitting the modulated optical signal from a light source into an optical fiber, the optical fiber including a plurality of sensing locations disposed along the optical fiber and configured to reflect light; receiving a reflected signal including light reflected from the plurality of sensing locations; and combining, in parallel, each of a plurality of reference signals with the reflected signal to estimate a value of the parameter.

A long range optical fiber sensor such as a distributed acoustic sensor has a sensing fiber located remotely from the interrogator, with a length of transport fiber path connecting the two. Because no sensing is performed on the transport fiber then the pulse repetition rate from the interrogator can be high enough such that the pulse repetition rate and pulse power are optimised according to the sensing fiber length and hence sensing frequency response and sensitivity are also optimised according to the sensing fiber length.

The present invention discloses an integrated system for optical fiber sensing and communication through sharing co-frequency resources. Specifically, the system consists of two parts: optical path detection and circuit demodulation. The entire system consists of a continuous wave laser, a fiber coupler, a polarization controller, a mach-zehnder modulator, an arbitrary waveform generator, an erbium-doped fiber amplifier, an optical filter, an optical fiber annular, an optical fiber, a photodetector, a data acquisition device, a balance detector and a data acquisition card. A transmission optical signal and a sensing detection light are generated by the same laser, transmission performance and sensing performance of the system are changed by adjusting modulation power of a transmission signal, the transmission signal is obtained by using direct detection at far-end, a sensing signal is obtained by using heterodyne coherent detection at local-end. The present invention provides a simple, compact and high-efficiency integrated system for co-frequency sharing optical fiber sensing and communication, to solve the deficiencies of the existing integrated system in practical applications.

An optical measurement system in which a coherent light source generates a light signal, and a launch stage receives the light signal from the light source and generates a test signal. The test signal is launched along an optical path. The launch stage includes a first IQ modulator for controlling the test signal. The optical measurement system further includes a local oscillator stage configured to generate a local oscillator signal, wherein local oscillator stage has a second IQ modulator for controlling the local oscillator signal. A detector stage of the system is configured to receive the local oscillator signal from the local oscillator stage and a scattered signal from the optical path, and interfere the local oscillator signal with the scattered signal. The optical measurement system is implemented with one or more photonic integrated circuits.

Provided is an optical fiber sensor that is capable of highly accurately detecting an abnormality in a structure from vibration information. This optical fiber sensor includes an optical fiber that is laid in the vicinity of a structure, a light source for introducing pulsed light of a specific period into the optical fiber, and an optical sensor for detecting return light that has been obtained as a result of the introduction of the pulsed light into the optical fiber. The structure is determined to have an abnormality if the spectral centroid of vibration information exceeds a threshold.

A multilinear domain-specific domain generalization (MDSDG) approach that utilizes information stored in multilinear indices of data domains to improve machine learning. In particularbased on limited sample size(s) in observed scenariosan array of models is jointly trained, which advantageously are generalized to a new, unseen scenario, where only domain descriptions in the form of multilinear indices are available.

A distributed acoustic sensing (DAS) system may include an optical fiber, a phase-sensitive OTDR (-OTDR) coupled to the optical fiber, and a processor cooperating with the -OTDR. The processor may be configured to generate a series of covariance matrices for DAS data from the -OTDR, and determine an acoustic event based upon comparing the series of covariance matrices with a corresponding Toeplitz matrix.