A system 1 for remote sensing of information to be transmitted, said system 1 comprising; an optical time-domain reflectometer, OTDR, 2 adapted to transmit an optical probe signal OPS into an optical fiber 3 and to measure a backscattered signal power; and at least one electro-optical signaling unit 4 connected to said optical fiber 3, wherein the electro-optical signaling unit 4 is configured to change an attenuation and/or a reflection of the optical probe signal OPS depending on at least one signal provided by one or more signal sources 5 in response to the information to be transmitted.

The subject matter of this specification can be embodied in, among other things, a method that includes separating, from a few mode optical fiber, a collection of backscattered Rayleigh signals based on a vibration of the few mode optical fiber at a vibration frequency at a first location along the few mode optical fiber, separating, from the few mode optical fiber, a collection of backscattered Stokes Raman signals and Anti-Stokes Raman signals based on a temperature of the few mode optical fiber at a second location along the few mode optical fiber, detecting the separated Rayleigh signals and Raman signals, determining, based on detecting the collection of backscattered Rayleigh traces, at least one of the first location, the vibration frequency, and an amplitude of the vibration, and determining, based on the detecting the collection of backscattered Raman signals, the temperature at the second location.

The present invention is to provide a backscattered light amplification device, an optical pulse test apparatus, a backscattered light amplification method, and an optical pulse test method for amplifying a desired propagation mode of Rayleigh backscattered light with a desired gain by stimulated Brillouin scattering in a fiber under test having the plurality of propagation modes. The backscattered light amplification device according to the present invention is configured to control individually power, incident timing, and pulse width of a pump pulse for each propagation mode when the pump pulse is incident in a plurality of propagation modes after the probe pulse is input to the fiber under test in any propagation mode.

A method of distributed fibre optic sensing is described. In an example, a series of interrogations are launched into an optical fibre, each interrogation comprising interrogating radiation in at least one pulse pair, wherein the pulses of a pulse pair are introduced to the optical fibre with a time interval therebetween. Radiation backscattered therefrom is sampled, so as to obtain at least one sample from each interrogation. Phase modulation in the samples is determined and components of the phase modulation which are below a threshold frequency are isolated. Such a method of sensing could be used, for example, to monitor changes in temperature of the optical fibre.

An arrangement for distributed acoustic sensing and sensor integrity monitoring is adapted to operate in a first operation mode and in a second operation mode. In the first operation mode, the arrangement injects a first light pattern (and successively injects a second light pattern having substantially the same wavelength, both light patterns generated using a light launching module, into the fiber; determines a backscatter change between first backscatter dependent light and second backscatter dependent light detected by the detector, to determine a time change of a characteristic of the fiber. In the second operation mode, the arrangement injects another first light pattern and successively another second light pattern; to determine a backscatter average of other first backscatter dependent light and other second backscatter dependent light detected by the detector, to determine a static characteristic of the fiber.

A computer-implemented event statistic generation for intrusion detection comprises processing a plurality of return signals from a coherent optical time-domain reflectometer into time-domain signals for each of a plurality of sensor bins, the plurality of return signals corresponding to a plurality of stimulation pulses injected into an optical sensor fiber during a time period. For each sensor bin, transforming the respective time-domain signal into a corresponding frequency-domain signal, calculating, from the respective frequency-domain signal, a first signal power area of a first frequency band expected to contain system noise and a second signal power area of a second frequency band expected to contain any energy related to at least a first event; and generating an event statistic proportional to the ratio of the second signal power area to the first signal power area at least in part by dividing the second signal power area by the first signal power area.

It is described a method and arrangement of fibre optic distributed sensing for detection of an event at an event location within a blind region, the method comprising: using at least one optical fibre arranged at least partly along an object to be monitored and at least one light pattern interrogator coupled with the optical fibre; injecting light patterns at subsequent times; detecting backscatter light from the light patterns; and analysing the backscatter light to determine the event location.

A temperature sensor for measuring temperature is described. The sensor comprises a fibre optic cable (104) comprising optical fibre (102) and an interrogator unit (106) configured to interrogate the optical fibre with electromagnetic radiation, detect any radiation that is Rayleigh backscattered within the optical fibre and determine a measurement signal indicative of temperature changes for at least one longitudinal sensing portion of the optical fibre. A controllable thermal element, which may be a heating element, such as an electrically conducting element (108), is arranged along the length of the fibre optic cable (104) and in thermal communication with the fibre optic cable (104). A controller (110) is configured to generate a thermal variation in the controllable thermal element, e.g. by generating a time varying electric current in the electrically conducting element (108). An analyser (112) is configured to analyse the measurement signal, extract a thermal response signal corresponding to the thermal variation and compare the thermal response to a predetermined characteristic to determine the temperature of the fibre optic cable at said longitudinal sensing portion.

In some implementations, a device may obtain responsivity data for segments of a fiber optic cable. The device may receive, from a sensor device, vibration data associated with the fiber optic cable, the vibration data being produced by a vibration source in or on soil associated with the fiber optic cable. The device may normalize, based on the responsivity data, the vibration data. The device may determine, based on the normalized vibration data, a distance of the vibration source from the fiber optic cable. The device may perform one or more actions based on the distance satisfying a distance threshold.

A distributed acoustic system (DAS) method and system. The system may comprise an interrogator and an umbilical line comprising a first fiber optic cable and a second fiber optic cable attached at one end to the interrogator. The DAS may further include a downhole fiber attached to the umbilical line at the end opposite the interrogator and a light source disposed in the interrogator that is configured to emit a plurality of coherent light frequencies into the umbilical line and the downhole fiber. The method may include generating interferometric signals of the plurality of frequencies of backscattered light that have been received by the photo detector assembly and processing the interferometric signals with an information handling system.