EP0129972A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Polarised light optical sensing arrangements
Assignee: BAE Systems Electronics Ltd
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Filing: 1984-05-14
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Granted: —
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Expires: 2004-05-14
Abstract
Abstract Polarised light is applied for the detection of acoustic waves and/or temperature or magnetic field changes, to the input end (5) of an optical sensor (1) for transmission therethrough. A path length difference is produced between orthogonal components of the polarised light at the output end of the optical sensor (1), and path length optical compensation means (4) is optically coupled to and so oriented with respect to the input end or output end of the sensor, that the path length difference between the orthogonally polarised components transmitted through the compensator means (4) and the corresponding path length difference in the optical sensor (1) are mutually opposite, thereby reducing the noise content of an output signal derived from the arrangement and fed to polarisation analyser means (3) for producing an indication of structural changes which have occurred in the optical sensor.
Inventors
- 👤 John Philip Dakin
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 22:18
CPC Classifications
G; G01; G01H; G01H9/00; G01H9/004; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/344
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
156 words
An optical sensing arrangement suitable for the detection of acoustic waves and/or temperature or magnetic field changes, comprising means for producing polarised light which in operation of the arrangement will be applied for detection purposes to the input end of an optical sensor for transmission therethrough, whereby a path length difference is produced between orthogonal components of the polarised light at the output end of the optical sensor, characterised in that path length optical compensation means is optically coupled to and so orientated with respect to the input end or output end of the sensor, that the path length difference between the orthogonally polarised components transmitted through the compensation means and the corresponding path length difference in the optical sensor are mutually opposite, thereby reducing the noise content of an output signal derived from the arrangement and fed to polarisation analyser means for producing an indication of structural changes which have occurred in the optical sensor.
Claim 2
Dependent Claim
156 words
An optical sensing arrangement suitable for the detection of acoustic waves and/or temperature or magnetic field changes, comprising means for producing polarised light which in operation of the arrangement will be applied for detection purposes to the input end of an optical sensor for transmission therethrough, whereby a path length difference is produced between orthogonal components of the polarised light at the output end of the optical sensor, characterised in that path length optical compensation means is optically coupled to and so orientated with respect to the input end or output end of the sensor, that the path length difference between the orthogonally polarised components transmitted through the compensation means and the corresponding path length difference in the optical sensor are mutually opposite, thereby reducing the noise content of an output signal derived from the arrangement and fed to polarisation analyser means for producing an indication of structural changes which have occurred in the optical sensor.
Claim 3
Dependent Claim
31 words
An optical sensing arrangement as claimed in claim 1, in which the compensation means is interposed between the means for producing polarised light and the input end of the optical sensor.
Claim 4
Dependent Claim
37 words
An optical sensing arrangement as claimed in claim 1 or claim 2, in which the path length difference between the orthogonal components transmitted through the compensation means completely cancels the corresponding path difference in the optical sensor.
Claim 5
Dependent Claim
22 words
An optical sensing arrangement as claimed in claim 1, 2 or 3, in which the optical sensor comprises a polarisation-maintaining optical fibre.
Claim 6
Dependent Claim
40 words
An optical sensing arrangement as claimed in claim 4, in which the path length compensation means comprises a second polarisation-maintaining optical fibre which affords the same path length difference between the orthogonally polarised signals travelling therethrough as the optical sensor.
Claim 7
Dependent Claim
45 words
An optical sensing arrangement as claimed in claim 5, in which the two polarisation-maintaining optical fibres have their ends butt-jointed or fuse-welded together so that the two fibres are coaxial with their respective orthogonal polarisation axes angularly displaced with respect to one another by 90°.
Claim 8
Dependent Claim
51 words
An optical sensing arrangement as claimed in claim 4, in which the path length difference compensation means comprises a bi-refringent crystal which abuts one end of the optical fibre sensor and which has its orthogonal polarisation axes angularly rotated through 90° with respect to the corresponding axes of the sensor fibre.
Claim 9
Dependent Claim
18 words
An optical sensing arrangement as claimed in claim 2, in which the optical sensor comprises a bi-refringent crystal.
Claim 10
Dependent Claim
42 words
An optical sensing arrangement as claimed in claim 8, in which the compensation means comprises a bi-refringent crystal which abuts the sensor crystal and the orthogonal polarisation axes of the respective crystals being angularly rotated through 90° with respect to one another.
Claim 11
Dependent Claim
51 words
An optical sensing arrangement as claimed in claim 9, in which the optical sensor fibre is isolated from the path length difference compensation fibre so as to render the compensation fibre insensitive to temperature changes, magnetic field changes or the impingement of acoustic waves to be detected by the sensor fibre.
Claim 12
Dependent Claim
19 words
An optical fibre sensing arrangement substantially as herein before described with reference to Figure 2 of the accompanying drawing.
Claim 13
Dependent Claim
19 words
An optical fibre sensing arrangement substantially as herein before described with reference to Figure 2 of the accompanying drawing.
Claim 14
Dependent Claim
19 words
An optical fibre sensing arrangement substantially as herein before described with reference to Figure 3 of the accompanying drawing.
Claim 15
Dependent Claim
19 words
An optical fibre sensing arrangement substantially as herein before described with reference to Figure 3 of the accompanying drawing.
References Cited (Backward Citations)
US2441049A
Cited
US4198123A
Cited
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