| 1. |
- Holm, Ulf, et al.
(författare)
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Transmission loss compensation for Faraday effect fibre optic sensors
- 1994
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Ingår i: SENSORS AND ACTUATORS A-PHYSICAL. - : Elsevier. ; , s. 487-490
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Konferensbidrag (refereegranskat)abstract
- We present a novel scheme for compensation of transmission loss variations in Faraday effect-based fibre optic magnetic field sensors. Light is sent through the sensing element in opposite directions to form the two signal channels needed for the compensation. Experiments have been made with a time-multiplexed multimode system in which IR emitting diodes are alternately used as emitters and detectors. With transmission loss variations of less than 25%, which is reasonable in a real system, the resulting error is well below 1%.
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| 2. |
- Sohlström, Hans, 1952-, et al.
(författare)
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A waveguide-based fiber optic magnetic field sensor with directional sensitivity
- 1991
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Ingår i: SPIE - The International Society for Optical Engineering, vol. 1511. - Bellingham, WA, United States : Int Soc for Optical Engineering. - 0819406201 ; , s. 142-148
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Konferensbidrag (refereegranskat)abstract
- Design and performance of an extrinsic guided wave fiber optic magnetic field sensor is reported. The sensor utilizes a substituted YIG (yttrium iron garnet, Y3Fe5O12) thin film as the waveguiding sensing element. A polarization maintaining fiber downlead was used to provide insensitivity to both power and loss fluctuations. The design makes it possible to determine both the magnitude and the sign of the magnetic field. Measurement results indicate a usable measurement range of at least several mT with a noise equivalent magnetic field level of less than 8 nT/√Hz
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| 3. |
- Sohlström, Hans, 1952-
(författare)
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Fibre Optic Magnetic Field Sensors Utilizing Iron Garnet Materials
- 1993
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the subject of fibre optic magnetic field sensors utilizing iron garnet materials. Such materials exhibit a large Faraday rotation which make them advantageous for application in compact magnetic field sensors. After an introduction, in which fibre optic sensors and optical methods to measure electric current are reviewed, the original research work is summarized. A system for the measurement of the magneto-optic properties of transparent materials is described. Measurement results, showing the influence of temperature, magnetic field direction and sample treatment on the magneto-optical properties of YIG-crystals, are presented. The properties of thin magneto-optical waveguiding films have also been studied using different light coupling methods. Measurement results obtained for holographic grating, prism and edge (end-fire) light coupling to different substituted YIG films are presented. It is shown that the launching method may affect the properties to be measured. The design and performance of several versions of extrinsic guided wave fibre optic magnetic field sensors are then reported. The sensors employ substituted YIG (Yttrium Iron Garnet, Y3Fe5O12) thin film waveguides as sensing elements. Polarization maintaining fibres were used as feed and return to provide two signal channels. The signals were combined in a balanced measurement system, providing insensitivity to both fluctuations in optical power and loss. Sensors have been made both with separate fibres to guide the light to and from the sensing element and with a single fibre for both functions. The two fibre version, although less ”elegant”, is found to have a better performance. This version also makes it possible to determine both the magnitude and sign of the magnetic field. Measurement results indicate a usable measurement range of at least several mT with a noise equivalent magnetic field level of less than 8 nT/root(Hz). The design and performance of multimode fibre optic magnetic field sensors utilizing the Faraday effect in an epitaxially grown thick (YbTbBi)IG film is also described. This type of sensor is found to be linear over a range from 27 mT to less than 270 nT. Sensor prototypes suitable for current monitoring in high voltage transmission lines have also been developed.
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| 4. |
- Sohlström, Hans, 1952-, et al.
(författare)
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The Performance Of A Fiber Optic Magnetic-Field Sensor Utilizing A Magnetooptical Garnet
- 1992
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Ingår i: Fiber and integrated optics (Print). - : Taylor & Francis. - 0146-8030 .- 1096-4681. ; 11:2, s. 135-139
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Tidskriftsartikel (refereegranskat)abstract
- The design and performance of a multimode fiber optic magnetic field sensor utilizing the Faraday effect in an epitaxially grown thick (YbThBi)IG film is reported. The sensor is found to be linear over a range of more than lOO dB.
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