GB2262803A - An optical fibre sensor array - Google Patents
An optical fibre sensor array Download PDFInfo
- Publication number
- GB2262803A GB2262803A GB9127358A GB9127358A GB2262803A GB 2262803 A GB2262803 A GB 2262803A GB 9127358 A GB9127358 A GB 9127358A GB 9127358 A GB9127358 A GB 9127358A GB 2262803 A GB2262803 A GB 2262803A
- Authority
- GB
- United Kingdom
- Prior art keywords
- sensor array
- optical
- fibre
- optical fibre
- redirecting
- 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- Withdrawn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 26
- 239000000835 fiber Substances 0.000 claims abstract description 22
- 238000001514 detection method Methods 0.000 claims abstract description 11
- 238000012544 monitoring process Methods 0.000 claims abstract description 7
- 230000003287 optical effect Effects 0.000 claims description 24
- 230000005540 biological transmission Effects 0.000 claims description 2
- 230000008878 coupling Effects 0.000 claims description 2
- 238000010168 coupling process Methods 0.000 claims description 2
- 238000005859 coupling reaction Methods 0.000 claims description 2
- 238000006073 displacement reaction Methods 0.000 claims description 2
- 230000000644 propagated effect Effects 0.000 claims description 2
- 238000005305 interferometry Methods 0.000 abstract 1
- 238000000034 method Methods 0.000 description 5
- 238000003491 array Methods 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 229920000271 Kevlar® Polymers 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000004761 kevlar Substances 0.000 description 1
- 230000004807 localization Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- 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
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/18—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength
- G08B13/181—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems
- G08B13/183—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems by interruption of a radiation beam or barrier
- G08B13/186—Actuation by interference with heat, light, or radiation of shorter wavelength; Actuation by intruding sources of heat, light, or radiation of shorter wavelength using active radiation detection systems by interruption of a radiation beam or barrier using light guides, e.g. optical fibres
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Length Measuring Devices By Optical Means (AREA)
- Optical Transform (AREA)
Abstract
A linear strain sensor is described, consisting of a cabled or jacketed optical fibre. Light travelling through the fibre, is phase modulated by the strain, which is detected using reflectometric interferometry. The sensor is suitable for intruder detection, structural monitoring and monitoring of vehicles on the highways. <IMAGE>
Description
An Optical Fibre Sensor Arrav This invention relates to an optical fibre sensor array, and in particular to such an array for detecting strain.
Optical fibres have been employed in many types of detection systems. One particular application in which they have previously been used is for the detection of acoustic pressure waves in water. In order to detect such pressure waves and to obtain information about the wave, for example directivity, it is necessary to employ a plurality of optical fibre sensors usually in a linear array. As such arrays are often towed behind a marine vessel optical sensors arrays for such applications have been developed so that the sensor array comprises of only optical fibre material, all contact with the array being by the propagation of light along the fibre, enabling all the electronics for producing the light signals and processing the received signals to be mounted remote from the array for example on board the marine vessel towing the array.
One such optical sensing system as described above is disclosed in our UK patent application Publication No. 2136113. This discloses a sensor array comprising a single optical fibre 6, having along its length discontinuities which define respective sensors comprising of the lengths of fibre between each adjacent pair of discontinuities. A similar arrangement is shown in our co-pending application number 9124589.4 wherein a plurality of light sources are used to send a plurality of light signals down a single fibre, with respective sets of optical sensing elements being associated with different light sources enabling a greater number of optical sensors to be deployed.
The present invention arose from the realisation that apparatus similar to that disclosed in the above referred to applications could be advantageously applied for detecting strain on the surface of, or within, a structure.
According to the present invention there is provided an optical fibre sensor array including an optical fibre, a light source for transmitting light signals into the fibre, and detector means, the fibre comprising a plurality of sensor elements, each being a length of the optical fibre positioned on, or under, a surface on which strain is to be detected, the lengths of optical fibre being defined by redirecting means for redirecting light signals propagated along the sensor array to the detecting means.
By providing an optical fibre sensor in accordance with the invention it is possible to sense strain at multiple locations, with the only connection required being by a single optical fibre. This provides that the electronic processing data and light source can be far removed from the sensed area and does not require electrical signals to be transmitted to the sensed area, which may be advantageous in areas of high fire risk.
Preferably the redirecting means comprises partial reflectors for reflecting light signals back along the single optical fibre to the detector arrangement such that only one fibre need be provided between the light source/detector arrangement and the sensor elements. These partial reflectors may be reflective optical couplers.
Alternatively the redirecting means may comprise optical coupling means for redirecting light to an optical fibre other than said single optical fibre for transmission to the optical detector arrangement.
Advantageously a reference cable is positioned in close proximity to the sensor array to permit common-mode noise to be cancelled, for example laser noise or geological noise, which would be common-mode rejected, leading to a lowering of the noise floor and hence an increase in sensitivity.
In certain applications it is desirable that the detection means comprises means for analysing the return signal and means for comparing it with stored data in order to classify the detection and thereby identify what has been detected.
Preferably the light source comprises a laser source and an optical switch for directing light from the laser source along two paths one of which has an optical delay therein and one of which has an optical phase shifter therein, such that in use the light source transmits to the fibre two time displaced pulses at different frequencies, such an arrangement permitting a semiconductor laser to be used as the light source.
An array in accordance with the invention can advantageously be employed for monitoring vehicles on a highway, for detecting an intruder, or for detecting displacement of machinery. Several embodiments of the invention will now be described by way of example only with reference to the accompanying drawings of which:
Figure 1 is a schematic illustration of an intruder detection system in accordance with the invention;
Figure 2 is a schematic diagram of a vehicle monitoring system in accordance with the invention;
Figure 3 is a schematic diagram of an alternative arrangement of the apparatus of Figure 2;
Figure 4 schematically illustrates a light source arrangement;
Figure 4a schematically illustrates the output of the light source of Figure 4; and
Figure 5 depicts one possible sensor arrangement in accordance with the invention.
The devices depicted in the Figures use the modulation of rays of light within the fibre caused by straining of the fibre.
Referring now to Figure 1 there is illustrated an intruder detection system comprising a control point 1 housing a light source and detector arrangement, a fibre optic cable 2 surrounded by a Kevlar* strain member and overlaid with a protective plastic jacket. Attached to the optical fibre 2 are optical couplers 3 forming reflective discontinuities which redirect part of the light signal propagating along the fibre from the light source in the control point 1 back to the detector in the control point.
Each section of fibre 4,5,6,7,8,9 and 10 between each pair of adjacent optical couplers 3 forms a sensor element.
These sensor elements are placed just below ground level so that they are strained by an intruder placing his weight on the ground in the region of these elements.
An intruder crossing the double line of buried sensors at 'A' will be detected by sensor 6, followed by sensor 8, providing speed and direction information. Sensors 6 and 8 are arranged so that their outputs are set to cancel each other in the electronic processing within the detector. In this case, any common mode ambient or instrumental variations due, for example, to laser noise or geological noise, will be common mode rejected, leading to a lowering of the noise floor and hence an increase in sensitivity.
* A TRADE MARK
In the example shown in Figure 1, a total invigilated length of 600 metres is shown, situated at a distance of 5Km form the control point 1. This can be greater both in detection length and in downlink length, with intruder localisation to within 100-200 metres.
Signal demodulation is carried out in control point 1 by methods currently used in optical hydrophone arrangements. Typical signatures, (footsteps for example), occupy a restricted frequency range (below 500Hz) and have a characteristic spectrum. Knowledge of this spectrum provides a method of classification, following detection (using for example a simple level detector). Matched filtering, and correlation techniques are used, with stored replica target characteristics.
Referring to Figure 2, another application is illustrated for monitoring vehicles on a highway 20. Fibres 21, similar to these described with reference to Figure 1, are laid under the highway 20 and monitor the axle weight and speed of vehicles crossing the cable, the amplitude of the signal being related to the force (and hence vehicle weight) impressed on the cable. The signals are generated at control point 23 which also processes the returned signals. A second set of reference cables could be placed close to the first set, to cancel the effects of common-mode noise from sources other than traffic.
An alternative approach which reduces installation costs on existing carrageways is illustrated in Figure 3.
Here the cables 31 are located at the side of the road (or in the central reservation). This is more difficult to calibrate and is less sensitive than the Figure 2 arrangement, but appropriate configuration of the cable run (either as, a column or zigzag) either in the surface of the roadside, or off the road, can allow satisfactory operation in certain applications.
A further application of the strain sensor (not illustrated) is for monitoring vibration of machinery, structures, aircraft etc. In these cases the cable is incorporated within the structure or attached to the outside. Vibration above 1-5Hz can be monitored, and any change in characteristics of the spectrum or amplitude detected. The advantage of this technique is the economical deployment of many sensors, so in this case, it would be of most advantage in very large structures such as ships, oil rigs etc.
Figure 4 depicts apparatus suitable as a light source for the systems described with reference to Figures 1 to 4.
This comprises a semiconductor laser 40 which generates light that passes through a switch 41 producing a pulse on fibre 41. The switch can be connected to produce pulses on similar lines 43 (only one of which is shown) leading to similar arrays. The pulse traveling along fibre 42 travels on two paths A and B. A fibre delay 44 in path A causes a pulse entering the system to leave as two separated pulses, as required for the multiplexing scheme. Also in path A there is an optical phase shifter 45 capable of providing a linear phase ramp on one of the pulses. This results in an effective optical frequency change on one of the pulses, as required. Timing of this scheme is shown in Figure 4a, in which a linear phase ramp is shown. Alternatively a phase sinusoid could be used, and switched only on the linear portion.The required phase ramp (or sinusoid) could be obtained in two ways, either by winding fibre on a piezoelectric "stretcher" mandrel, or by using an integrated optical phase shifter. The delay 44 can be a fibre coil.
Referring now to Figure 5, there is illustrated a variation on the apparatus previously described, wherein the optical couplers 51A and 51B are frequency dependant, 51A being transmissive to a first frequency W1, and 51B being transmissive to a second frequency W2. In this way sensor elements 53A and 53B only modify W1 or W2 respectively enabling extended arrays of sensors to be provided, as for example in this embodiment signals of wavelength W2 will not be attenuated by couplers 51A. These couplers can be reflective, as previously described, or alternatively as disclosed in Figure 5, couple signals to a return fibre 52.
Claims (13)
1. An optical fibre sensor array including an optical fibre, a light source for transmitting light signals into the fibre, and detector means, the fibre comprising a plurality of sensor elements, each consisting of a length of the optical fibre positioned on, or under, a surface on which strain is to be detected, the lengths of optical fibre being defined by redirecting means, the redirecting means redirecting light signals propagated along the sensor array to the detecting means.
2. A sensor array as claimed in any preceding claim wherein the redirecting means comprise partial reflectors for reflecting light signals back along the single optical fibre to the detector arrangement.
3. A sensor array as claimed in claim 2 wherein said reflectors comprise reflective optical couplers.
4. A sensor array as claimed in claim 1 wherein the redirecting means comprise optical coupling means for redirecting light signals to an optical fibre other than said optical fibre for transmission to the optical detector arrangement.
5. A sensor array as claimed in any preceding claim wherein a reference cable is positioned in close proximity to the sensor array to permit common-mode noise to be cancelled.
6. A sensor array as claimed in any preceding claim wherein the detection means comprises means for analysing the returned signal and means for comparing it with stored data in order to classify the detection.
7. A sensor array as claimed in any preceding claim wherein the light source comprises a laser source, and an optical switch for directing light from the laser source along two paths one of which has an optical delay therein and one of which has an optical phase shifter therein, such that in use the light source transmits to the fibre two time displaced pulses at different frequencies.
8. A sensor array as claimed in any one of claims 1 to 7, in which the light source comprises a Bragg cell for combining and launching light signals of different wavelengths into the single optical fibre, the Bragg cell being arranged to be pulsed sequentially at different predetermined frequencies in order to produce like deflections of incoming light signals at different wavelengths.
9. A sensor array as claimed in any preceding claim for-monitoring vehicles on a highway.
10. A sensor array as claimed in any one of claims 1 to 8 claim for detecting an intruder.
11. A sensor array as claimed in any one of claims 1 to 8 for detecting displacement of machinery.
12. A sensor array as claimed in any preceding claim comprising means for generating a plurality of light sources of different frequencies, and a plurality of sets of redirecting means, wherein different set of redirecting means are associated with different light sources.
13. An optical fibre sensor array substantially as hereinbefore described with reference to any one of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9127358A GB2262803A (en) | 1991-12-24 | 1991-12-24 | An optical fibre sensor array |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9127358A GB2262803A (en) | 1991-12-24 | 1991-12-24 | An optical fibre sensor array |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9127358D0 GB9127358D0 (en) | 1992-02-19 |
| GB2262803A true GB2262803A (en) | 1993-06-30 |
Family
ID=10706804
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9127358A Withdrawn GB2262803A (en) | 1991-12-24 | 1991-12-24 | An optical fibre sensor array |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2262803A (en) |
Cited By (27)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5757487A (en) * | 1997-01-30 | 1998-05-26 | The United States Of America As Represented By The Secretary Of The Navy | Methods and apparatus for distributed optical fiber sensing of strain or multiple parameters |
| WO2003042636A2 (en) * | 2001-11-14 | 2003-05-22 | Fiber Optic Systems Technology, Inc. | Fiber optic sensor |
| US6647161B1 (en) * | 1995-12-15 | 2003-11-11 | Malcolm H. Hodge | Structural monitoring sensor system |
| US6804008B1 (en) | 2001-11-14 | 2004-10-12 | Fiber Optic Systems Technology, Inc. | Fiber optic sensing instrument and system with fiber of adjustable optical path length and method of using it |
| US6870975B1 (en) | 2001-11-14 | 2005-03-22 | Fiber Optic Systems Technology, Inc. | Fiber optic sensor usable over wide range of gage lengths |
| GB2406376A (en) * | 2003-09-24 | 2005-03-30 | Qinetiq Ltd | Surveillance system including serial array of fiber optic point sensors |
| US7652245B2 (en) | 2005-10-25 | 2010-01-26 | Qinetiq Limited | Traffic sensing and monitoring apparatus |
| US7656535B2 (en) | 2004-12-17 | 2010-02-02 | British Telecommunications Public Limited Company | Optical system and method for inferring a disturbance |
| US7667849B2 (en) | 2003-09-30 | 2010-02-23 | British Telecommunications Public Limited Company | Optical sensor with interferometer for sensing external physical disturbance of optical communications link |
| US7697795B2 (en) | 2005-03-04 | 2010-04-13 | British Telecommunications Public Limited Company | Acoustic modulation |
| US7755971B2 (en) | 2005-03-04 | 2010-07-13 | British Telecommunications Public Limited Company | Sensing system |
| US7796896B2 (en) | 2003-09-30 | 2010-09-14 | British Telecommunications Plc | Secure optical communication |
| US7817279B2 (en) | 2006-02-24 | 2010-10-19 | British Telecommunications Public Limited Company | Sensing a disturbance |
| US7848645B2 (en) | 2004-09-30 | 2010-12-07 | British Telecommunications Public Limited Company | Identifying or locating waveguides |
| US7961331B2 (en) | 2006-02-24 | 2011-06-14 | British Telecommunications Public Limited Company | Sensing a disturbance along an optical path |
| US7974182B2 (en) | 2004-03-31 | 2011-07-05 | British Telecommunications Public Limited Company | Evaluating the position of a disturbance |
| US7995197B2 (en) | 2004-09-30 | 2011-08-09 | British Telecommunications Public Limited Company | Distributed backscattering |
| US8000609B2 (en) | 2005-04-14 | 2011-08-16 | British Telecommunications Public Limited Company | Communicating or reproducing an audible sound |
| US8003932B2 (en) | 2005-06-02 | 2011-08-23 | British Telecommunications Public Limited Company | Evaluating the position of a disturbance |
| US8027584B2 (en) | 2006-02-24 | 2011-09-27 | British Telecommunications Public Limited Company | Sensing a disturbance |
| US8045174B2 (en) | 2004-12-17 | 2011-10-25 | British Telecommunications Public Limited Company | Assessing a network |
| WO2012164260A1 (en) * | 2011-06-01 | 2012-12-06 | Detection Technologies Ltd | Security system, controller for a security system, transducing cable for a security system and method for detecting a disturbance and determining the location of the disturbance |
| US8396360B2 (en) | 2005-03-31 | 2013-03-12 | British Telecommunications Public Limited Company | Communicating information |
| US8670662B2 (en) | 2006-04-03 | 2014-03-11 | British Telecommunications Public Limited Company | Evaluating the position of an optical fiber disturbance |
| WO2014170013A1 (en) * | 2013-04-17 | 2014-10-23 | Eth Zurich | Fibre optic based intrusion sensing system |
| EP2846316A1 (en) * | 2013-09-05 | 2015-03-11 | ETH Zurich | Fibre optic based intrusion sensing system |
| CN114061569A (en) * | 2021-11-23 | 2022-02-18 | 武汉理工大学 | Vehicle track tracking method and system based on grating array sensing technology |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2126820A (en) * | 1982-07-17 | 1984-03-28 | Plessey Co Plc | An optical sensing system |
| GB2190262A (en) * | 1986-05-09 | 1987-11-11 | Stc Plc | Optical fibre sensor |
| GB2202046A (en) * | 1987-03-11 | 1988-09-14 | Plessey Co Plc | Optical fibre sensor arrangement |
| GB2209212A (en) * | 1987-09-01 | 1989-05-04 | Plessey Co Plc | Optical sensing systems |
| GB2214636A (en) * | 1988-01-29 | 1989-09-06 | Plessey Co Plc | Optical sensing apparatus |
| GB2250593A (en) * | 1990-12-06 | 1992-06-10 | Marconi Gec Ltd | Optical sensing system |
-
1991
- 1991-12-24 GB GB9127358A patent/GB2262803A/en not_active Withdrawn
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2126820A (en) * | 1982-07-17 | 1984-03-28 | Plessey Co Plc | An optical sensing system |
| GB2190262A (en) * | 1986-05-09 | 1987-11-11 | Stc Plc | Optical fibre sensor |
| GB2202046A (en) * | 1987-03-11 | 1988-09-14 | Plessey Co Plc | Optical fibre sensor arrangement |
| GB2209212A (en) * | 1987-09-01 | 1989-05-04 | Plessey Co Plc | Optical sensing systems |
| GB2214636A (en) * | 1988-01-29 | 1989-09-06 | Plessey Co Plc | Optical sensing apparatus |
| GB2250593A (en) * | 1990-12-06 | 1992-06-10 | Marconi Gec Ltd | Optical sensing system |
Cited By (31)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6647161B1 (en) * | 1995-12-15 | 2003-11-11 | Malcolm H. Hodge | Structural monitoring sensor system |
| US5757487A (en) * | 1997-01-30 | 1998-05-26 | The United States Of America As Represented By The Secretary Of The Navy | Methods and apparatus for distributed optical fiber sensing of strain or multiple parameters |
| WO2003042636A2 (en) * | 2001-11-14 | 2003-05-22 | Fiber Optic Systems Technology, Inc. | Fiber optic sensor |
| WO2003042636A3 (en) * | 2001-11-14 | 2004-01-22 | Fiber Optic Systems Technology | Fiber optic sensor |
| US6804008B1 (en) | 2001-11-14 | 2004-10-12 | Fiber Optic Systems Technology, Inc. | Fiber optic sensing instrument and system with fiber of adjustable optical path length and method of using it |
| US6870975B1 (en) | 2001-11-14 | 2005-03-22 | Fiber Optic Systems Technology, Inc. | Fiber optic sensor usable over wide range of gage lengths |
| GB2406376A (en) * | 2003-09-24 | 2005-03-30 | Qinetiq Ltd | Surveillance system including serial array of fiber optic point sensors |
| US7965909B2 (en) | 2003-09-24 | 2011-06-21 | Qinetiq Limited | Fibre-optic surveillance system |
| US7667849B2 (en) | 2003-09-30 | 2010-02-23 | British Telecommunications Public Limited Company | Optical sensor with interferometer for sensing external physical disturbance of optical communications link |
| US7796896B2 (en) | 2003-09-30 | 2010-09-14 | British Telecommunications Plc | Secure optical communication |
| US7974182B2 (en) | 2004-03-31 | 2011-07-05 | British Telecommunications Public Limited Company | Evaluating the position of a disturbance |
| US7848645B2 (en) | 2004-09-30 | 2010-12-07 | British Telecommunications Public Limited Company | Identifying or locating waveguides |
| US7995197B2 (en) | 2004-09-30 | 2011-08-09 | British Telecommunications Public Limited Company | Distributed backscattering |
| US8045174B2 (en) | 2004-12-17 | 2011-10-25 | British Telecommunications Public Limited Company | Assessing a network |
| US7656535B2 (en) | 2004-12-17 | 2010-02-02 | British Telecommunications Public Limited Company | Optical system and method for inferring a disturbance |
| US7755971B2 (en) | 2005-03-04 | 2010-07-13 | British Telecommunications Public Limited Company | Sensing system |
| US7697795B2 (en) | 2005-03-04 | 2010-04-13 | British Telecommunications Public Limited Company | Acoustic modulation |
| US8396360B2 (en) | 2005-03-31 | 2013-03-12 | British Telecommunications Public Limited Company | Communicating information |
| US8000609B2 (en) | 2005-04-14 | 2011-08-16 | British Telecommunications Public Limited Company | Communicating or reproducing an audible sound |
| US8003932B2 (en) | 2005-06-02 | 2011-08-23 | British Telecommunications Public Limited Company | Evaluating the position of a disturbance |
| US7652245B2 (en) | 2005-10-25 | 2010-01-26 | Qinetiq Limited | Traffic sensing and monitoring apparatus |
| US8027584B2 (en) | 2006-02-24 | 2011-09-27 | British Telecommunications Public Limited Company | Sensing a disturbance |
| US7961331B2 (en) | 2006-02-24 | 2011-06-14 | British Telecommunications Public Limited Company | Sensing a disturbance along an optical path |
| US7817279B2 (en) | 2006-02-24 | 2010-10-19 | British Telecommunications Public Limited Company | Sensing a disturbance |
| US8670662B2 (en) | 2006-04-03 | 2014-03-11 | British Telecommunications Public Limited Company | Evaluating the position of an optical fiber disturbance |
| WO2012164260A1 (en) * | 2011-06-01 | 2012-12-06 | Detection Technologies Ltd | Security system, controller for a security system, transducing cable for a security system and method for detecting a disturbance and determining the location of the disturbance |
| WO2014170013A1 (en) * | 2013-04-17 | 2014-10-23 | Eth Zurich | Fibre optic based intrusion sensing system |
| US9679451B2 (en) | 2013-04-17 | 2017-06-13 | Eth Zurich | Fibre optic based intrusion sensing system |
| EP2846316A1 (en) * | 2013-09-05 | 2015-03-11 | ETH Zurich | Fibre optic based intrusion sensing system |
| CN114061569A (en) * | 2021-11-23 | 2022-02-18 | 武汉理工大学 | Vehicle track tracking method and system based on grating array sensing technology |
| CN114061569B (en) * | 2021-11-23 | 2022-12-23 | 武汉理工大学 | Vehicle track tracking method and system based on grating array sensing technology |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9127358D0 (en) | 1992-02-19 |
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