GB2137767A - Optical fibre transducer - Google Patents
Optical fibre transducer Download PDFInfo
- Publication number
- GB2137767A GB2137767A GB08306015A GB8306015A GB2137767A GB 2137767 A GB2137767 A GB 2137767A GB 08306015 A GB08306015 A GB 08306015A GB 8306015 A GB8306015 A GB 8306015A GB 2137767 A GB2137767 A GB 2137767A
- Authority
- GB
- United Kingdom
- Prior art keywords
- transducer
- optical fibre
- coils
- loops
- line
- 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.)
- Granted
Links
- 239000013307 optical fiber Substances 0.000 title claims abstract description 52
- 230000005540 biological transmission Effects 0.000 claims abstract description 4
- 239000011159 matrix material Substances 0.000 claims description 9
- 239000000835 fiber Substances 0.000 description 7
- 238000010276 construction Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 238000003491 array Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 238000005192 partition Methods 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0128—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on electro-mechanical, magneto-mechanical, elasto-optic effects
- G02F1/0131—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on electro-mechanical, magneto-mechanical, elasto-optic effects based on photo-elastic effects, e.g. mechanically induced birefringence
- G02F1/0134—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on electro-mechanical, magneto-mechanical, elasto-optic effects based on photo-elastic effects, e.g. mechanically induced birefringence in optical waveguides
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
- G01L1/242—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre
- G01L1/243—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre using means for applying force perpendicular to the fibre axis
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
- G01L11/02—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means
- G01L11/025—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means using a pressure-sensitive optical fibre
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Optics & Photonics (AREA)
- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
Abstract
A transducer formed from optical fibre the light transmission property of which is responsive to pressure variation. The optical fibre is distributed to provide an array in which the concentration of optical fibre is greater towards the centre.
Description
SPECIFICATION
Optical fibre transducer
This invention relates to a transducer formed
from optical fibre the light transmission property
of which is responsive to pressure.
Experiments have shown that optical fibre light
guides are responsive to pressure variation due to
sound waves in that light passing therethrough is
phase modulated by the sound field due to a
combination of mechanical (change in length) and
optoelastic (changes of refractive index) effects on
the fiber. Accordingly, such a light guide can be
used as a pressure transducer and the light
transmitted thereby can be fed to a photodetector
which provides an output signal representative of
pressure variation. Such a transducer is useful for
a variety of applications e.g. an underwater
acoustic sensor or a geophonic signal sensor.By
providing an array of such transducers e.g. an in
line array their combined output has directional
responses in that it is sensitive to pressure waves
arrangement will also have so called side lobe
responses in that it is sensitive to pressure wave
originating from more than one direction.
The present invention seeks to provide a
transducer in which side lobe responses are
reduced.
According to the invention there is provided a
transducer formed from optical fiber the light
transmission property of which is responsive to pressure variation, wherein the optical fibre is
distributed to provide an array in which the concentration of optical fibre is greater towards the centre.
The transducer may comprise a plurality of substantially in line elongate loops of optical fibre which loops extend in their elongate direction to opposite sides of a central axis which loops are of different elongate lengths the number of turns in each loop being related to its elongate length such taht shorter loops have more turns thereby to provide said concentration of optical fibre which is greater towards the centre of the array in one axial direction. A plurality of additional lines of elongate loops of optical fibre may be provided similar to said in line elongate loops which additional lines are spaced from and substantially parallel to said in line elongate loops.The arrangement may be such that the number of turns in similarly disposed loops is greatest for the intermediate line(s) and reduces progressively for lines spaced outwardly from the intermediate line(s) thereby to provide a concentration of optical fibre which is greater towards the centre of the array in two axial directions. A former may be provided having progressively spaced support means on which the loops are wound. The former may be of ladder like configuration having a plurality of rungs which form said support means.
One alternative configuration for the transducer is where the optical fibre is arranged in concentric rings.
Another alternative configuration is wherein the optical fibre is wound to provide a line of coils disposed side b.1?side the number of turns being greatest for the intermediate coil(s) and reducing progressively for coils spaced outwardly from the intermediate coils. A plurality of additional lines of coils may be provided spaced from and parallel to said line of coils to form a matrix array, the number of turns in coils disposed in different lines in a direction transversely of the lines being greatest for the intermediate coil(s) and reducing progressively for coils spaced outwardly from the intermediate coils. The coils may be wound on bobbins and mounted on receiving locations on a support. Alternatively, there may be provided a partitioned support defining a matrix of recesses into which coils of optical fibre are distributed.
Another possibility is that the optical fibre is wound helically.
In one advantageous form the transducer is formed from a continuous optical fibre. However, the loops, coils or rings of optical fibre can be formed from individual fibres.
In order that the invention and its various other preferred features may be understood more easily, some embodiments thereof will now be described, by way of example only, with reference to the drawings, in which:
Figure 1 shows a line array of transducers,
Figure 2 shows the response characteristics of the array of Figure 1 and a desired characteristic,
Figure 3 is a schematic elevational view of an optical fibre hydrophone array constructed in accordance with the invention,
Figure 4 is a matrix showing turns for each coil or loop in an array six lines each having three pairs of coils or loops,
Figure 5 is an embodiment of the invention employing a matrix of spaced coils,
Figure 6 is an embodiment of the invention employing a support of egg box like form,
Figure 7 is an embodiment of the invention employing concentric rings of optical fibre, and
Figure 8 is an embodiment of the invention employing a helically wound optical fibre.
The drawing of Figure 1 shows a transducer array comprising a line of transducer elements 10 receiving a source of sound from direction A which is inclined to the normal by an angle x. Figure 2 shows in solid line the combined response of such an array as the sound source angle is varied. It will be seen that the response is a maximum when x = 0 but that side lobe responses occur at other angles. The closest side lobe response is only about -1 3dB and this makes directional sensing difficult particularly when interference signals of amplitudes, similar to that of a required signal, are present. An ideal response of a transducer array is shown in Figure 2 in dotted line.
In order to improve the directional response of such an array it is necessary to enhance the sensitivity of the central transducer elements relative to the outer elements and by arranging that the sensitivities of transducers are progressively reduced with distance from the centre, a response which approximates to the ideal can be obtained.
A particularly convenient construction of
acoustic sensor suitable for operating as a
hydrophone and implementing this principle in
optical fibre is illustrated in Figure 3. In this
construction a framework 20 is formed from
tubular material and is of ladder like form
comprising two side arms 21, 22 and pairs of
rungs Si, S2 and S3. The outer rungs S3 as can
be seen are in this example disposed at the ends
of the side arms 21 and 22 and form therewith a
rectangular construction. The rungs of each pair
S1, S2 and S3 are equally spaced one to each side
of a transverse central axis between the two arms
21 and 22. Elongate coils or loops L1, L2 and L3
of optical fibre are wound around each pair of
rungs and extend in line along the framework.
These coils form effectively three in line
transducers similar to the arrangement of Figure 1
but as will be appreciated the density of optical
fibre at the centre i.e. between supports S1 will be greaterthan between S1 and S2 and greater still
than between S2 and S3 because every turn or
loop wound round supports S2 result in additional
fibre being provided between supports S1 and
every turn or loop wound round supports S3 result
in additional fibre being provided between
supports L1 and between L1 and L2.By
appropriate choice of the turns ratio the central
response can be enhanced relative to the outer response so that the combined output of the coils provides a desired shading function which approximates to the ideal value shown in dotted line in Figure 2. A single line array 31 of this type would provide directional response in one plane and constitutes a simple construction in accordance with the invention. However, Figure 3 has additional similar lines 32, 33, 34 of elongate coils or loops wound on the same framework parallel to the previously described line array 31.
By arranging that the number of turns or loops in the coils in the intermediate line arrays 32, 33 are less than in the outer arrays 31 and 34 the central response in the quadrature plane can be enhanced relative to the outer response and the shading effect of the combined outputs of the coils in all lines can be arranged to provide directional information in two planes.
The coils or loops are preferably wound from a single continuous optical fibre but can be wound as separate coils or loops from individual fibres. In the embodiment of Figure 3 the dimensions of the framework are 2m x 1 m but it will be appreciated that frameworks of smaller or greater dimensions can be produced to suit specific required beam apertures. The numbers of pairs of winding supports SI--SN can be varied and the numbers of lines Ll-LN of fibre loops can be varied to suit specific applications and provide a desired response. The response can be calculated.In practice it has been found that a configuration having six lines of loops each having three coils can be made to approximate quite closely to a required shading function in which side lobes are -30dB. In such a construction the number of turns in each loop are shown in a matrix in Figure 4. In the matrix turns are shown as constituting the extremities of each coil or loop i.e. each coil or loop has two extremities so the figures are repeated. This is to illustrate the way in which fibre density increases towards the centre of the array i.e. the centre of the matrix.Although the embodiment of Figure 3 is implemented on a ladder like framework it will be appreciated that a similar configuration of loops could be provided with a different means of support e.g. by providing a support formed of sheet material provided with projecting pegs spaced apart in lines and around which the fibre is wound, or by providing a support of sheet material provided with holes therethrough disposed in lines and the fibre is wound between and through pairs of holes.
There are other configuration which permit the provision of an array in which the distribution of optical fibre is greater towards the centre some examples of which will now be described and are intended to fall within the scope of this invention.
Figure 5 illustrates an array in which a base support 50 is provided with receiving locations in the form of lines of spaced projecting pegs 51 on which there are provided coils 52 of optical fibre either wound directly thereon or on bobbins. The coils have different numbers of turns to provide different sensitivities across the array. The number of turns on the coils are greatest at the centre and reduce progressively with distance from the centre of the array. In the preferred arrangement illustrated, the coils are wound from a single continuous optical fibre.
Figure 6 shows an embodiment in which a base 60 is of egg box like construction providing partitioned recesses 61 disposed in lines and columns into which an optical fibre can be wound or distributed. The amount of optical fibre provided in the centre partitions of the array is greatest and reduces progressively for partitions further from the centre. In the preferred arrangement illustrated a single continuous optical fibre is distributed through the recesses.
Figure 7 shows an embodiment in which the array is made up of concentric rings 70 of optical fibre. The density of optical fibre in the centre ring is greatest whilst the density of optical fibre in the outer rings reduces progressively with distance from the centre. In the preferred arrangement illustrated the rings are all wound from a single continuous optical fibre.
In each of the embodiments 3 to 7 the loops, coils or rings can be wound from individual fibres and can be optically coupled prior to routing to an optical detector or can each be fed to an optical detector to provide signals for subsequent processing. In the latter case the signais can be directly combined or can have weighting factors applied to provide for beam stearing of the array.
In the embodiments involving individual coils difficulties can arise in the response across the aperture due to coil resonances. The embodiment of Figure 3 is less susceptible to such effects due to relatively large winding dimensions.
Another embodiment of particularly simple form is shown in Figure 8. Here, a single optical fibre is wound helically the pitch of the helix being small at the centre and gradually increasing with distance from the centre so that the concentration of optical fibre is greatest at the centre and reduces progressively with distance from the centre.
Claims (14)
1. A transducer formed from optical fibre and light transmission property of which is responsive to pressure variation, wherein the optical fibre is distributed to provide an array in which the concentration of optical fibre is greater towards the centre.
2. A transducer as claimed in claim 1, comprising a plurality of substantially in line elongate loops of optical fibre which loops extend in their elongate direction to opposite sides of a central axis which loops are of different elongate lengths the number of turns in each loop being related to its elongate length such that shorter loops have more turns thereby to provide said concentration of optical fibre which is greater towards the centre of the array in one axial direction.
3. A transducer as claimed in claim 2, comprising a plurality of additional lines of elongate loops of optical fibre similar to said in line elongate loops which additional lines are spaced from and substantially parallel to said in line elongate loops.
4. A transducer as claimed in claim 3, wherein the number of turns in similarly disposed loops is greatest for the intermediate line(s) and reduces progressively for lines spaced outwardly from the intermediate line(s) thereby to provide a concentratiqn of optical fibre which is greater towards the centre of the array in two axial directions.
5. A transducer as claimed in any one of claims 2, 3 or 4, comprising a former having progressively spaced support means on which the loops are wound.
6. A transducer as claimed in claim 5, wherein the former is of ladder like configuration having a plurality of rungs which form said support means.
7. A transducer as claimed in claim 1, wherein the optical fibre is arranged in concentric rings.
8. A transducer as claimed in claim 1, wherein the optical fibre is wound to provide a line of coils disposed side by side, the number of turns being greatest for the intermediate coil(s) and reducing progressively for coils spaced outwardly from the intermediate coils.
9. A transducer as claimed in claim 8, comprising a plurality of additional lines of coils spaced from and parallel to said line of coils to form a matrix array, the number of turns in coils disposed in different lines in a direction transversely of the lines being greatest for the intermediate coil(s) and reducing progressively for coils spaced outwardly from the intermediate coils.
10. A transducer as claimed in claim 8 or 9, wherein the coils are wound on bobbins and are mounted on receiving locations on a support.
ii. A transducer as claimed in claim 9, comprising a partitioned support defining a matrix of recesses into which coils of optical fibre are distributed.
12. A transducer as claimed in claim 1, wherein the optical fibre is wound helically.
13. A transducer as claimed in any one of the preceding claims formed from a continuous optical fibre.
14. A transducer as claimed in any one of claims 2 to ii, wherein the loops, coils or rings of optical fibre are formed from individual fibres.
1 5. A transducer substantially as described herein with reference to the drawings.
1 6. A hydrophone comprising a transducer as claimed in any one of the preceding claims.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08306015A GB2137767B (en) | 1983-03-04 | 1983-03-04 | Optical fibre transducer |
| AU25201/84A AU578411B2 (en) | 1983-03-04 | 1984-03-01 | Optical fibre transducer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08306015A GB2137767B (en) | 1983-03-04 | 1983-03-04 | Optical fibre transducer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2137767A true GB2137767A (en) | 1984-10-10 |
| GB2137767B GB2137767B (en) | 1987-01-14 |
Family
ID=10538993
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08306015A Expired GB2137767B (en) | 1983-03-04 | 1983-03-04 | Optical fibre transducer |
Country Status (2)
| Country | Link |
|---|---|
| AU (1) | AU578411B2 (en) |
| GB (1) | GB2137767B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005116601A2 (en) * | 2004-05-25 | 2005-12-08 | Polarmetrix Limited | Method and apparatus for detecting pressure distribution in fluids |
| US7872736B2 (en) | 2004-11-03 | 2011-01-18 | Fotech Solutions Limited | Detecting a disturbance in the propagation of light in an optical waveguide |
-
1983
- 1983-03-04 GB GB08306015A patent/GB2137767B/en not_active Expired
-
1984
- 1984-03-01 AU AU25201/84A patent/AU578411B2/en not_active Ceased
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005116601A2 (en) * | 2004-05-25 | 2005-12-08 | Polarmetrix Limited | Method and apparatus for detecting pressure distribution in fluids |
| WO2005116601A3 (en) * | 2004-05-25 | 2006-08-03 | Polarmetrix Ltd | Method and apparatus for detecting pressure distribution in fluids |
| US7940389B2 (en) | 2004-05-25 | 2011-05-10 | Fotech Solutions Limited | Method and apparatus for detecting pressure distribution in fluids |
| US7872736B2 (en) | 2004-11-03 | 2011-01-18 | Fotech Solutions Limited | Detecting a disturbance in the propagation of light in an optical waveguide |
Also Published As
| Publication number | Publication date |
|---|---|
| AU2520184A (en) | 1984-09-06 |
| GB2137767B (en) | 1987-01-14 |
| AU578411B2 (en) | 1988-10-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732 | Registration of transactions, instruments or events in the register (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19930304 |