摘要:
Techniques and apparatus are provided for downhole sensing using optical couplers in a downhole splitter assembly to split interrogating light signals into multiple optical sensing branches. Each optical branch may then be coupled to an optical sensor (e.g., a pass-through or an optical single-ended transducer (OSET)) or to another optical coupler for additional branching. The sensors may be pressure/temperature (P/T) type transducers. Some systems may exclusively use OSETs as the optical sensors. In this manner, if one of the OSETs is damaged, it does not affect light traveling to any of the other sensors, and sensing information from remaining sensors is still returned.
摘要:
The application describes methods and apparatus for distributed fiber sensing, especially distributed acoustic/strain sensing. The method involves launching interrogating radiation in to an optical fiber and sampling radiation backscattered from within said fiber at a rate so as to acquire a plurality of samples corresponding to each sensing portion of interest. The plurality of samples are divided into separate processing channels and processed to determine a phase value for that channel. A quality metric is then applied to the processed phase data and the data combined to provide an overall phase value for the sensing portion based on the quality metric. The quality metric may be a measure of the degree of similarity of the processed data from the channels. The interrogating radiation may comprise two relatively narrow pulses separated by a relatively wide gap and the sampling rate may be set such that a plurality of substantially independent diversity samples are acquired.
摘要:
A method for diminishing the signal interference of a transmission path of an optical fibre interference system, belonging to the technical field of optical fibre sensing. A wavelength division multiplexer (19) is connected in series to the end of an induced optical fibre, a wavelength component (λ2) is separated from an operating path by means of the wavelength division multiplexer (19) so as to measure a signal picked up by a transmission path, and the signal is removed from overall interference sensing signals by taking same as a reference, thereby obtaining a target measurement signal. Also provided is a structure for diminishing the signal interference of a transmission path of an optical fibre interference system. The method and the structure are simple; moreover, the device connected to the end of an induced optical fibre is passive, so that power supply is not required, and it is easy to implement. The present invention can be used for a sensing structure with a single measurement point and can be used in a sensing structure with a plurality of discontinuous measurement points as well.
摘要:
A multiple sensor fiber optic sensing system includes an optical fiber having at least first fiber optic sensors and second fiber optic sensors deployed along its length. In response to an interrogating pulse, the first fiber optic sensors generate responses in a first optical spectrum window, and the second fiber optic sensors generate responses in a second, different optical spectrum window. The responses in the first optical spectrum window are measured in a first optical spectrum channel, and the responses in the second optical spectrum window are measure in a second, different optical spectrum channel and provide simultaneous indications of one or more parameters, such as temperature and pressure, in the environment in which the sensors are deployed.
摘要:
The invention relates to a fibre-optic sensor comprising an optical waveguide having at least one first core and a cladding surrounding the first core, wherein the first core extends substantially over the entire length of the optical waveguide, wherein the sensor has at least one second core which is at least partly surrounded by the cladding, wherein the longitudinal extent of the second core is less than the total length of the optical waveguide and at least one Bragg grating is introduced into the second core. Furthermore, the invention relates to a use of the fibre-optic sensor.
摘要:
The present invention relates to an optical fiber for a fiber optic sensor, comprising a first optical grating adapted to operate over a first range of wavelengths; and at least one set of further gratings adapted to operate over a second range of wavelengths, each grating being adapted to operate over a portion of the second range; wherein, each grating within said set has an operating range that partially overlaps with at least one other such grating operating range. The invention also extends to a sensor system, and method, using such an optical fiber.
摘要:
A plurality of AWG filters with aliasing responses are selected such that the wavelength range of a fundamental response of the AWG filters results in the aliased range of AWG filters to be adjacent to a fundamental range of the AWG filters. A plurality of optical sources is provided sufficient to cover each fundamental wavelength range and each alias wavelength range of the AWG filters. When a single one of the optical sources is enabled, reflected optical energy from a series string of FBGs coupled to the optical source is applied to the plurality of AWG filters, and the AWG output in combination with the wavelength range of the optical source is used to discriminate reflected wavelength from the FBG sensors.
摘要:
There is disclosed a distributed optical fiber sensor arranged to deliver probe light pulses of different wavelengths into corresponding different sensing optical fibers, and to determine one or more parameters as functions of position along each of the sensing fibers from detected backscattered light of each corresponding wavelength. In another arrangement, the different wavelengths are directed in different corresponding directions around a loop of sensing optical fiber.
摘要:
Methods and apparatus enable monitoring conditions in a well-bore using multiple cane-based sensors. The apparatus includes an array of cane-based Bragg grating sensors located in a single conduit for use in the well-bore. For some embodiments, each sensor is located at a different linear location along the conduit allowing for increased monitoring locations along the conduit.
摘要:
A method and system for multiplexing a network of parallel fiber Bragg grating (FBG) sensor-fibers to a single acquisition channel of a closed Michelson interferometer system via a fiber splitter by distinguishing each branch of fiber sensors in the spatial domain. On each branch of the splitter, the fibers have a specific pre-determined length, effectively separating each branch of fiber sensors spatially. In the spatial domain the fiber branches are seen as part of one acquisition channel on the interrogation system. However, the FBG-reference arm beat frequency information for each fiber is retained. Since the beat frequency is generated between the reference arm, the effective fiber length of each successive branch includes the entire length of the preceding branch. The multiple branches are seen as one fiber having three segments where the segments can be resolved. This greatly simplifies optical, electronic and computational complexity, and is especially suited for use in multiplexed or branched OFS networks for SHM of large and/or distributed structures which need a lot of measurement points.