The disclosure relates to a distributed optical fibre sensor having an optical switch arranged to selectively and simultaneously couple each of a plurality of interrogators to each of a plurality of sensing optical fibres.

A sensor network having a series arrangement of fiber-coupled, reflective sensors is disclosed. In operation, a first light signal having multiple wavelength bands is launched in an upstream direction on a fiber bus. Each sensor includes a wavelength filter and an FP sensor that is sensitive to a parameter. Each wavelength filter (1) selectively passes a different one of the wavelength bands to its FP sensor and (2) reflects the remaining wavelength bands back into the fiber bus to continue upstream. The FP sensor imprints a signal based on the parameter onto its received light and reflects it as a second light signal. The collimator, wavelength filter, and FP sensor of each sensor are arranged such that each second light signal is returned to the fiber bus, which conveys them in a downstream direction to a processor that measures them and estimates the parameter at each sensor.

The invention relates to an apparatus (110) and a method (152) for determining a deformation (170) of a three-dimensional, flexible structure in form of a tubular construct (112). Here, at least one optical waveguide (116) is introduced into the tubular construct (112), wherein the optical waveguide (116) extends in form of a helical winding (118) within the tubular construct (116) and has a multiplicity of strain measuring means (126). The apparatus (110) further comprises at least one evaluation device (130) which is configured to determine the deformation of the tubular construct (112), in particular in relation to an axis, surface and/or volume of the construct (112), from measurement values (154) from the multiplicity of strain measuring means (126).

Aspects of the present disclosure describe systems, methods, and structures for distributed temperature sensing that employ joint wavelet denoising to achieve desirable signal-to-noise ratio(s) over extended sensor fiber distances.

Distributed acoustic sensing (DAS) system for quasi-coherent detection of at least one multi-frequency signal over an optical fiber, including a multi-frequency pulse generator, a circulator, a coherent detector and a processor, the pulse generator for generating at least one multi-frequency pulse train including at least two pulses each having a different frequency, the pulse train including a plurality of carriers, the coherent detector for receiving at least one backscattered signal from the optical fiber and the processor for quasi-coherent aggregation of the carriers in the backscattered signal, wherein the processor channelizes the backscattered signal into at least one complex signal for each frequency in the carriers and wherein for each complex signal, the processor respectively extracts at least one of an amplitude change and a phase change for each one of the carriers and selectively aggregates at least one of the changes for the carriers for determining if an event has occurred over the optical fiber.

There is described a method for interrogating optical fiber comprising fiber Bragg gratings (FBGs), using an optical fiber interrogator. The method comprises (a) generating an initial light pulse from phase coherent light emitted from a light source, wherein the initial light pulse is generated by modulating the intensity of the light; (b) splitting the initial light pulse into a pair of light pulses; (c) causing one of the light pulses to be delayed relative to the other of the light pulses; (d) transmitting the light pulses along the optical fiber; (e) receiving reflections of the light pulses off the FBGs; and (f) determining whether an optical path length between the FBGs has changed from an interference pattern resulting from the reflections of the light pulses.

The present invention relates to an optical measuring system comprising a polymer-based single-mode fibre-optic sensor system (102), an optical interrogator (101), and an optical arrangement (103) interconnecting the optical interrogator (101) and the polymer-based single-mode fibre-optic sensor system (102). The invention further relates to an optical interrogator adapted to be connected to a polymer-based single-mode fibre-optic sensor system via an optical arrangement. The interrogator comprises a broadband light source arrangement (104) and a spectrum analysing arrangement which receives and analyses light reflected from the polymer-based single-mode fibre-optic sensor system.

A method and apparatus for monitoring a structure using an optical fiber based distributed acoustic sensor (DAS) extending along the length of the structure. The DAS is able to resolve a separate acoustic signal with a spatial resolution of 1 m along the length of the fibre, and hence is able to operate with an acoustic positioning system to determine the position of the riser with the same spatial resolution. In addition, the fiber can at the same time also detect much lower frequency mechanical vibrations in the riser, for example such as resonant mode vibrations induced by movement in the surrounding medium. By using vibration detection in combination with acoustic positioning then overall structure shape monitoring can be undertaken, which is useful for vortex induced vibration (VIV) visualisation, fatigue analysis, and a variety of other advanced purposes. The structure may be a sub-sea riser.

A photoelectric sensor includes a connecting section for light projection to which a light propagation member for light projection optically coupled to a light emitting element is connected, a connecting section for light reception to which a light propagation member for light reception optically coupled to the light receiving element is connected, a signal generating unit configured to compare a light reception signal generated by the light receiving element and a threshold and generate a detection signal indicating a result of the comparison, a first light emitting element for indication optically coupled to the connecting section for light reception, and a mounting substrate on which each of the first light emitting element for indication and the light receiving element is positioned in the connecting section for light reception or one of the first light emitting element for indication and the light receiving element is positioned via the other.

An apparatus, system and method determining a position of an instrument (100) are provided. A sheath (104) is configured to fit within an instrument channel of a medical scope. An optical fiber (112) is disposed within the sheath and a plurality of sensors (106) is integrated in optical fiber. The sensors are configured to measure deflections and bending in the optical fiber. A fixing mechanism (140) is sized to fit within the instrument channel in a first state and fixes the sheath within the instrument channel in a second state such that the fixing mechanism anchors the sheath and the optical fiber so that the deflections and bending in the optical fiber are employed with a pre-procedural volumetric image to determine a position of the instrument.