Sensing Method and Sensor System A sensing method comprises using a vertical cavity surface emitting laser (VCSEL) to oscillate and emit a laser beam. A diaphragm is used to reflect a portion of the laser beam back into the VCSEL. This method can be referred as self mixing interferometry. A current or voltage at the VCSEL is monitored, and is used to sense movement of the diaphragm. This allows a property external to the VCSEL to be sensed without using a photo-detector.

Sensing Method and Sensor System A sensing method comprises using a vertical cavity surface emitting laser (VCSEL) to oscillate and emit a laser beam. A diaphragm is used to reflect a portion of the laser beam back into the VCSEL. This method can be referred as self mixing interferometry. A current or voltage at the VCSEL is monitored, and is used to sense movement of the diaphragm. This allows a property external to the VCSEL to be sensed without using a photo-detector.

Methods and apparatus to control the acoustic properties of optical cables used as in-well oil and gas probes for acoustic monitoring, such as distributed acoustic sensing (DAS). One example aspect provides a solid path for the acoustic wave to propagate from an outside armor layer of the cable to the sensing optical waveguide embedded therein. Another example aspect offers ways to spatially dispose the optical sensing elements to create response delays indicative of the propagation speed and/or direction of an acoustic wave. Yet another example aspect provides ways to utilize additional spectral interrogation to increase ultimate spatial resolution. Yet another example aspect provides ways to locally vary the acoustic properties along the length of the cable.

A method for automatic diagnosis of a mechanical system of a group of mechanical systems sharing mechanical characteristics includes obtaining data relating to a vibration. The vibration-related data is acquired by a portable communications device configured to communicate with a remote processor. The processor automatically diagnoses the mechanical system by applying a relationship to the obtained vibration-related data. The relationship is based on sets of vibration-related data previously obtained from the mechanical systems. Each set of vibration-related data relates to vibrations of a mechanical system. The relationship is further based on sets of operation data previously obtained for mechanical systems of the group. Each set of operation data indicates a previous state of operation of a mechanical system. Each of the previous states of operation is associated with at least one of the previously obtained sets of vibration-related data.

In a processing apparatus, a vibration detecting unit includes a light source, an interference unit configured to apply light emitted from the light source to a measurement target member and generate an interference pattern image. A control unit includes a storage section configured to store a first interference pattern image captured at a predetermined timing by the imaging unit and a second interference pattern image captured at a timing different from the timing of the first interference pattern image by the imaging unit, a comparing section configured to compare the first interference pattern image and the second interference pattern image stored in the storage section with each other, and a vibration detecting section configured to detect vibration on the basis of the first interference pattern image and the second interference pattern image compared with each other by the comparing section.

In a processing apparatus, a vibration detecting unit includes a light source, an interference unit configured to apply light emitted from the light source to a measurement target member and generate an interference pattern image. A control unit includes a storage section configured to store a first interference pattern image captured at a predetermined timing by the imaging unit and a second interference pattern image captured at a timing different from the timing of the first interference pattern image by the imaging unit, a comparing section configured to compare the first interference pattern image and the second interference pattern image stored in the storage section with each other, and a vibration detecting section configured to detect vibration on the basis of the first interference pattern image and the second interference pattern image compared with each other by the comparing section.

A system for processing DAS VSP surveys in real-time is provided. The system includes a DAS data collection system coupled to at least one optical fiber at least partially positioned within a wellbore and configured to repeatedly activate a seismic source of energy. The system further includes an information processing system connected to the DAS data collection system. A seismic dataset is received from the DAS data collection system. The seismic dataset includes a plurality of seismic data records. Two or more of the plurality of seismic data records are combined into a stack. A quality metric indicative of a desired signal-to-noise ratio or incoherence of the stack is determined for each processed seismic dataset collected from a repeated source. Instructions are sent to the DAS data collection system to stop activating the seismic source, in response to determining that the quality metric has reached a predefined threshold.

An acoustic system and method is disclosed for providing spatial and temporal classification of a range of different types of sound producing targets in a geographical area. The system includes an optical signal transmitter arrangement for repeatedly transmitting, at multiple instants, interrogating optical signals into each of one or more optical fibres distributed across the geographical area and forming at least part of an installed fibre-optic communications network. An optical signal detector arrangement receives, during an observation period following each of the multiple instants, returning optical signals scattered in a distributed manner over distance along the one or more of optical fibres. A processing unit demodulates acoustic data from the optical signals, processes the acoustic data and classifies it in accordance with the target classes or types to generate a plurality of datasets including classification, temporal and location-related data, and a storage unit stores the datasets in parallel with raw acoustic or optical data which is time and location stamped so that it can be retrieved for further processing.

In order to provide a detection device that is capable of detecting the submersion of a fiber-optic cable in water before water penetrates the interior of the fiber-optic cable, a detection system 1 comprises: a vibration-detecting fiber-optic cable 20; a receiving means 11 that receives an optical signal including vibrations detected by the fiber-optic cable 20; and a detection means 12 that detects submersion of the fiber-optic cable in water on the basis of the vibrations included in the optical signal.

Some embodiments are directed to a multiplexed fiber sensor for a fiber optic hydrophone array, including a signal receiver configured to receive a signal from the fiber optic hydrophone sensor array and an interferometer. The interferometer is configured to produce a first signal component and a second signal component from the signal received from the hydrophone array, and also provided with a first polarisation controller configured to control the polarisation of the first signal component and a second polarisation controller configured to control the polarisation of the second signal component. A modulated carrier signal generator configured to generate a modulated carrier signal component based on the first signal component is also provided. A detector configured to output a demodulated output signal from the modulated signal component and the second signal component is included, wherein the modulated signal component and the second signal component output separately from the interferometer.