GB2243210A - Distributed optical fibre sensor - Google Patents
Distributed optical fibre sensor Download PDFInfo
- Publication number
- GB2243210A GB2243210A GB8919551A GB8919551A GB2243210A GB 2243210 A GB2243210 A GB 2243210A GB 8919551 A GB8919551 A GB 8919551A GB 8919551 A GB8919551 A GB 8919551A GB 2243210 A GB2243210 A GB 2243210A
- Authority
- GB
- United Kingdom
- Prior art keywords
- optical
- fibre
- sensor
- signal
- optical fibre
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 239000013307 optical fiber Substances 0.000 title claims abstract description 17
- 239000000835 fiber Substances 0.000 claims abstract description 18
- 230000001427 coherent effect Effects 0.000 claims abstract description 7
- 238000001514 detection method Methods 0.000 claims abstract description 6
- 230000003111 delayed effect Effects 0.000 claims abstract description 5
- 238000001228 spectrum Methods 0.000 claims description 6
- 238000010899 nucleation Methods 0.000 claims 1
- 230000010355 oscillation Effects 0.000 claims 1
- 230000003287 optical effect Effects 0.000 abstract description 30
- 239000004020 conductor Substances 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 3
- 230000002269 spontaneous effect Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 240000006108 Allium ampeloprasum Species 0.000 description 1
- 238000012935 Averaging Methods 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- 101150071746 Pbsn gene Proteins 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000035559 beat frequency Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000005350 fused silica glass Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
- G01B11/18—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge using photoelastic elements
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35383—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using multiple sensor devices using multiplexing techniques
Abstract
The sensor uses the coherent detection of Stimulated Brillouin backscatter to detect temperature, strain and any external parameter which affects the frequency and or amplitude and or phase of the optical backscatter. The light from a laser is modulated 3 with pseudo-random noise 8 before being launched down an optical fibre 7. As shown, the backscattered light is modulated 13 with a delayed version of the pseudo-random noise before being detected, eg using a photoconductive mixer 10. alternatively, Fig 7 (not shown), the optical modulator 13 is removed and an electrical modulator is used in the photoconductive mixer. These arrangements can be modified by applying an optical source (15) to the other end of the fibre, Figs 8 and 9 (not shown). The Fig 6 arrangement can be modified by also applying the output of the modulator 13 to the other end of the fibre via an optical amplifier (16, Fig 10 not shown). <IMAGE>
Description
Optical fibre sensor
There is often a requirement to measure enviromental parameters at a number of different points. Optical fibre sensors can be built where light is launched into an optical fibre and the backscatter or forward scatter is measured. External enviromental parameters can be deduced by measuring the spectrum and or amplitude and or phase of the optical backscatter or optical forward scatter or optical transmission. By using radar techniques it is possible to obtain spatially resolved information about the parameter to be measured.
Distributed sensors using spontaneous backscatter generated in an optical fibre suffer problems due to the extremely low optical power levels reaching the detector and therefore often require considerable signal averaging. Stimulated Brillouin Scattering can provide a large conversion of the launched laser power into a frequency-shifted optical signal propagating backwards. The low threshold powers necessary for
Stimulated Brillouin Backscatter hereafter defined as SBS to occur in mono-mode fibres allows SBS to be usefully be employed in distributed fibre sensors.
A system is described which demonstrates the coherent detection of SBS from an optical fibre using an InP photo-conductor configured as a three-wave mixer which mixes two optical signals and a microwave signal, all within the same device.
This patent application is an extension of Patent Number 8611405 entitled "Greatly enhanced spatial detection of optical backscatter for sensor applications".
A CW non distributed sensor is described to show the principle of operation where in this system Stimulated Brillouin Scattering (SBS) from an optical fibre is coherent detected using an InP photo-conductive three-wave mixer. In this mixer two optical signals offset by aproximately 33GHz where this frequency is dependent on the laser frequency and the material properties of the optical fibre and the external enviromental parameters are multiplied together with a microwave signal, all within the same device, to produce an output signal of a few hundred MHz. This arrangement is used to measure the temperature and strain in an optical fibre as the temperature and strain is dependent on the frequency of the backscatter.
This mixer is described in Patent application number 8816250 entitled "Low noise opto-electronic correlators and mixers".
The system is shown in Figure 1 where light from a single mode 514 nm
Argon lon laser (1) where other single mode lasers can also be used was launched into a single mode optical fibre (6) via a Faraday optical isolator (2) and glass slide beam splitter (4) and lens or launch optics (5) where the isolator was placed at the output of the laser to ensure adequate isolation between the laser and the backscattered light from the fibre. The front face Fresnel reflection from the optical fibre (6) and or the reflected light from mirror (3) and the stimulated Brillouin backscatter from the fibre were directed on to a confocal Fabry Perot spectrum analyser (8) and photo-conductive 3-wave mixer (9), by the glass slide beam splitters (4 and 7).The photo-conductive mixer (9) was driven by a tunable 100 mw waveguide Gunn oscillator (26 - 40 Ghz) (10) via an attenuator and or isolator (11) and waveguide-to-OSSM adapter.
The frequency range of the Gunn oscillator was chosen to span the expected Brillouin frequency shift: approximately 33 GHz for fused silica at 514 nm4. The output from the photo-conductive three wave mixer (9)was then fed directly into a 50 Hz to 1.8 GHz spectrum analyser (12).
The photo-conductive mixer consists of a coplanar transmission line, with a central gap, evaporated on to an iron doped semi-insulating substrate of
InP as shown in Figure 2. Parallel configurations can also be used where the centre line now has no gap and the light is shone between the centre line and the ground plane. Metal tabs should be connected to the centre line and or the shunt line to reduce the gap to enhance the sensistivity or the detector. The tapers at either end are used to interface the detector with OSSM connectors. When the gap is illuminated by the Fresnel and
Brillouin backscatter a conducting plasma is produced whose conductance varies at the difference frequency between the two optical signals. An RF local oscillator is applied to one terminal and is arranged to switch the direction of the carriers.This is therefore a single balanced mixer with both an optical and electrical local oscillator. The photo-conductive mixer (9) can also be made in microstip and other types of transmission line.
When the system is roughly aligned the Fresnel reflection is seen on the
Fabry Perot spectrum analyser as shown in Figure 3. The Fabry Perot has a 2 GHz free spectral range and it can be seen that the laser was operating in single mode. The Stimulated Brillouin line appeared (see Figure 4) when the input coupler was adjusted to optimise the launched light into the core of the fibre. The microwave local oscillator frequency was set to 33
GHz which caused the beat frequency of the two optical waves to be down-converted into the pass band of the RF spectrum analyser (see
Figure 5). This detected signal could be tuned down and then up again in frequency as the microwave local oscillator was varied from one side of the Stimulated Brillouin signal to the other side. The microwave local oscillator may injection lock to the Brillouin signal at frequencies within 200 MHz.This is possibly due to the fact that the photo-conductor does not have perfect ohmic contacts and therefore some of the optical signal was detected and coupled back into the oscillator. This effect can be reduced by using microwave isolators (11) or by altering the attenuation, however the later lowers the signal level.
The gap of the present device is 20 lim, however new devices have been manufactured on the Plessey MMIC GaAs foundry service to produce much smaller gaps. A low impedance can be presented to the microwave signal on the low frequency output side of the detector. The low frequency output port can drive a PINFET or transimpedance amplifier. Therefore the noise performance can be optimised both at the microwave and low frequencies.
The frequency and amplitude and phase of both the stimulated and spontaneous Brillouin backscatter can be measured to determine the temperature or strain or any external parameter affecting the fibre.
A distributed sensor using the coherent detection of spontaneous or
Stimulated Brillouin backscatter is described which detects temperature, strain and any external parameter which affects the frequency and or amplitude and or phase of the optical backscatter.
A distributed sensor is shown in Figure 6 where the single mode laser (1) launches light through an optical isolator (2) then through a beam splitter (5) where one output goes into an optical modulator (3) and thence via beam splitter (40) and launch optics (6) into an optical fibre (7). The backscatter light from the fibre passes through the optics (6) and goes along the path via beam splitters 40 and 41 and 42 where the light is recombined with the light from beam splitter (5) and then passed through modulator (13). The two light signals are then incident on the photo-conductive 3 wave mixer (10) which is driven by a microwave oscillator (11) via an isolator (12) where the output is incident on an anlyser (14) which can measure the amplitude and frequency and phase of the output of the photo-conductor (10).The modulator (3) is driven by an electrical circuit which generates a digital pseudo-random noise signal and modulator (13) is driven by a delayed version of the pseudo random code where the code could be for example a binary maximal length pseudo random sequence or a Golay code or other noise like codes. The modulators can be used to amplitude or phase or frequency modulate the optical signals where for phase or frequency modulation the modulator (13) is arrange to cancel the origional modulation on the backscattered light with the same delay as the delay generated in the delay circuit (9). When amplitude modulation is used both modulators will be arranged to transmit the signal when the delay of the backscattered light is the same as the delay in the delay circuit (9). By varying the delay in the delay circuit (9) the variation of the amplitude and or frequency and or phase of the backscattered light can be measured at different points along the fibre whereby the value of the external parameters can be deduced. By scanning the delay in the delay circuit (9) the variation of the amplitude frequency and phase of the backscatter can be measured over all the points in the whole fibre. The distance along the fibre L that is measured occurs when 2Uc = t where t is the time delay set in the delay circuit (9) where c is the propagation velocity of the light in the fibre. and 2L/c is the round trip time of the light. The beam splitter (15) and the Fabry
Perot (16) are not essential but can be used to aid alignment of the system.The analyser may well need to be gated with the delayed PRBS code when amplitude modulation is used to enable accurate measurement of the frequency and or amplitude of the output signal from the photo-conductor. The photo-conductor and Gunn oscillator can be replaced with a photo-diode and mixer and oscillator to detect the signal at the microwave frequency and then downconvert the signal to a low frequency using a conventional local oscillator and mixer.
The system shown in Figure 7 can also be used where the optical modulator (13) shown in Figure 6 is now removed and an electrical modulator (13) is put in between the gunn oscillator(11 ) isolator(12) combination and the photo-conductive mixer (10). Again amplitude or frequency or phase modulation can be used.
The systems shown in Figures 6 and 7 can be modified as in Figures 8 and 9 by applying an optical source (15) whose optical frequency covers the range of frequencies over which the backscatter will occur. This could be used to increase the amount of optical signal returning from the fibre because of the optical gain in the fibre.
Figure 10 shows a system similar to Figure 6 except that now the optical output from the modulator (13) is applied to a beams splitter (15) and then optical amplifier (16) and then into the far end of the fibre via lauch optics 17. The loop including the fibre beams splitters 40 and 41 and 42 and modulator (13) and optical amplifier (16) are then made to oscillate at the optical Brillouing frequency by arranging for the loop gain to be greater than 1. The signal detected on the photo-conductive mixer in the same way as the system in Figure 6. The delay around the loop must be equal to the time before the sequence repeats. This system may well only work for phase or frequency modulation although it may also work with amplitude modulation.
Claims (6)
- Optical Fibre SensorClaims 1. A distributed optical fibre sensor conprising a light source, means for modulating with a pseudo-random or any noise like code sequence, means for launching the light source into the optical fibre, means for modulating the return signal with delayed version of noise like code where the modulation is performed optically prior to coherent detection, means for coherent detection and downconversion, means to produce a signal indicative of the spectrum or intensity of the stimulated or Spontaineous Brillouin backscatter which is indicative of the the spatial temperature or strain distribution along the fibre.
- 2. A sensor as claimed in claim 1 in which the returned backscattered signal is directly incident on the coherent detector and the delayed noise like code is multiplied electrically with the detected signal.
- 3. A sensor as claimed in claim 1 in which the light source modulation is amplitude modulation, frequency modulation or phase modulation or any combination thereof.
- 4. A sensor as claimed in claim 1 where if stimulated Brillouin Backscatter is being measured a seeding signal is provided at the far end of the fibre.
- 5. A sensor as claimed in claim 1 in which a complete loop is formed where the gain is greater than 1 causing oscillation at the frequency to be measured.
- 6. A distributed optical fibre sensor substantially as described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8919551A GB2243210A (en) | 1989-08-30 | 1989-08-30 | Distributed optical fibre sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8919551A GB2243210A (en) | 1989-08-30 | 1989-08-30 | Distributed optical fibre sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8919551D0 GB8919551D0 (en) | 1989-10-11 |
| GB2243210A true GB2243210A (en) | 1991-10-23 |
Family
ID=10662235
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8919551A Withdrawn GB2243210A (en) | 1989-08-30 | 1989-08-30 | Distributed optical fibre sensor |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2243210A (en) |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2710150A1 (en) * | 1993-09-17 | 1995-03-24 | Cortaillod Cables Sa | Method for measuring the Brillouin scattering in an optical fibre and device for implementing this method |
| US7283216B1 (en) | 2004-06-22 | 2007-10-16 | Np Photonics, Inc. | Distributed fiber sensor based on spontaneous brilluoin scattering |
| WO2008047329A2 (en) * | 2006-10-19 | 2008-04-24 | University Of Johannesburg | Method and apparatus for distributed sensing with strokes-locked reference laser |
| ITRA20080047A1 (en) * | 2008-11-21 | 2010-05-22 | Fibersens S R L | MEASUREMENT APPARATUS |
| WO2010058438A1 (en) * | 2008-11-21 | 2010-05-27 | Fibersens S.R.L. | Optoelectronic measuring apparatus for distributed physical characteristic |
| ITRA20090014A1 (en) * | 2009-04-21 | 2010-10-22 | Fibersens S R L | MEASUREMENT APPARATUS |
| WO2011039142A1 (en) * | 2009-10-01 | 2011-04-07 | Lios Technology Gmbh | Apparatus and method for spatially resolved temperature measurement |
| US20110088462A1 (en) * | 2009-10-21 | 2011-04-21 | Halliburton Energy Services, Inc. | Downhole monitoring with distributed acoustic/vibration, strain and/or density sensing |
| WO2012084040A1 (en) | 2010-12-22 | 2012-06-28 | Omnisens Sa | A brillouin optoelectronic measurement method and apparatus |
| US8584519B2 (en) | 2010-07-19 | 2013-11-19 | Halliburton Energy Services, Inc. | Communication through an enclosure of a line |
| WO2014155400A2 (en) | 2013-03-29 | 2014-10-02 | Bastiannini Filippo | Apparatus for interrogating distributed stimulated brillouin scattering optical fibre sensors using a quickly tuneable brillouin ring laser |
| WO2015170355A1 (en) | 2014-05-05 | 2015-11-12 | Filippo Bastianini | Apparatus for interrogating distributed optical fibre sensors using a stimulated brillouin scattering optical frequency-domain interferometer |
| US9823373B2 (en) | 2012-11-08 | 2017-11-21 | Halliburton Energy Services, Inc. | Acoustic telemetry with distributed acoustic sensing system |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2190186A (en) * | 1986-05-09 | 1987-11-11 | Dr Jeremy Kenneth Arth Everard | Greatly enhanced spatial detection of optical backscatter for sensor applications |
| GB2225505A (en) * | 1988-07-07 | 1990-05-30 | Jeremy Kenneth Arthur Everard | Low noise optoelectronic correlators and mixers |
| CH677281A5 (en) * | 1988-08-30 | 1991-04-30 | Asea Brown Boveri | Optical time domain reflectometry system - uses complementary pseudo-random pulse sequence for compensating reflections |
-
1989
- 1989-08-30 GB GB8919551A patent/GB2243210A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2190186A (en) * | 1986-05-09 | 1987-11-11 | Dr Jeremy Kenneth Arth Everard | Greatly enhanced spatial detection of optical backscatter for sensor applications |
| GB2225505A (en) * | 1988-07-07 | 1990-05-30 | Jeremy Kenneth Arthur Everard | Low noise optoelectronic correlators and mixers |
| CH677281A5 (en) * | 1988-08-30 | 1991-04-30 | Asea Brown Boveri | Optical time domain reflectometry system - uses complementary pseudo-random pulse sequence for compensating reflections |
Cited By (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2710150A1 (en) * | 1993-09-17 | 1995-03-24 | Cortaillod Cables Sa | Method for measuring the Brillouin scattering in an optical fibre and device for implementing this method |
| US7283216B1 (en) | 2004-06-22 | 2007-10-16 | Np Photonics, Inc. | Distributed fiber sensor based on spontaneous brilluoin scattering |
| WO2008047329A2 (en) * | 2006-10-19 | 2008-04-24 | University Of Johannesburg | Method and apparatus for distributed sensing with strokes-locked reference laser |
| WO2008047329A3 (en) * | 2006-10-19 | 2008-06-12 | Univ Johannesburg | Method and apparatus for distributed sensing with strokes-locked reference laser |
| ITRA20080047A1 (en) * | 2008-11-21 | 2010-05-22 | Fibersens S R L | MEASUREMENT APPARATUS |
| WO2010058438A1 (en) * | 2008-11-21 | 2010-05-27 | Fibersens S.R.L. | Optoelectronic measuring apparatus for distributed physical characteristic |
| ITRA20090014A1 (en) * | 2009-04-21 | 2010-10-22 | Fibersens S R L | MEASUREMENT APPARATUS |
| US9157810B2 (en) | 2009-10-01 | 2015-10-13 | Lios Technology Gmbh | Apparatus and method for spatially resolved temperature measurement |
| WO2011039142A1 (en) * | 2009-10-01 | 2011-04-07 | Lios Technology Gmbh | Apparatus and method for spatially resolved temperature measurement |
| US20110088462A1 (en) * | 2009-10-21 | 2011-04-21 | Halliburton Energy Services, Inc. | Downhole monitoring with distributed acoustic/vibration, strain and/or density sensing |
| US20130091942A1 (en) * | 2009-10-21 | 2013-04-18 | Halliburton Energy Services, Inc. | Downhole monitoring with distributed acoustic/vibration, strain and/or density sensing |
| US8584519B2 (en) | 2010-07-19 | 2013-11-19 | Halliburton Energy Services, Inc. | Communication through an enclosure of a line |
| US9003874B2 (en) | 2010-07-19 | 2015-04-14 | Halliburton Energy Services, Inc. | Communication through an enclosure of a line |
| US9116119B2 (en) | 2010-12-22 | 2015-08-25 | Omnisens Sa | Brillouin optoelectronic measurement method and apparatus |
| WO2012084040A1 (en) | 2010-12-22 | 2012-06-28 | Omnisens Sa | A brillouin optoelectronic measurement method and apparatus |
| US9823373B2 (en) | 2012-11-08 | 2017-11-21 | Halliburton Energy Services, Inc. | Acoustic telemetry with distributed acoustic sensing system |
| WO2014155400A2 (en) | 2013-03-29 | 2014-10-02 | Bastiannini Filippo | Apparatus for interrogating distributed stimulated brillouin scattering optical fibre sensors using a quickly tuneable brillouin ring laser |
| WO2015170355A1 (en) | 2014-05-05 | 2015-11-12 | Filippo Bastianini | Apparatus for interrogating distributed optical fibre sensors using a stimulated brillouin scattering optical frequency-domain interferometer |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8919551D0 (en) | 1989-10-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |