• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.419-427
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• 1996

Thermally-stabilized fiber-optic current sensors are proposed and demonstrated. The sensor head is made of two coil formers combined perpendicularly. In this sensor head, bending-induced birefringences can be reduced to the level much smaller than those of the single former type because the eigen-axes of the two perpendicular coil formers are made orthogonal to each other. Moreover, thermal variation of the birefringence is also expected to be minimized by the orthogonality of the two polarization eigen-axes. We changed the temperature slowly in the range of 20~45$^{\circ}C$ during 100 minutes. The overall linearity of the sensor is better than 1.2% in the range of 0~1000A. The long-term fluctuation of the sensor is less than 1% when measured for 3 hours at 500A and room temperature. Two orthogonally-polarized laser diodes are combined together to make the incident beam unpolarized. In the signal processing, the signals are separated by two parts and normalized respectively, which minimize the efects of optical fluctuations coming from sources, connectors, etc.

• Elastomers and Composites
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• v.48 no.4
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• pp.306-311
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• 2013

A series of liquid crystalline polyesters containing the 4-chloro benzoate group on the hydroquinone unit of rigid group were synthesized through solution polymerization of 2,5-di(4-chlorobenzoate)hydroquinones and 4,4'-dicarboxy-${\alpha},{\omega}$-diphenoxy alkane. The structure and properties for synthesized polymers were investigated by $^1H$-NMR, FT-IR, DSC, TGA, and POM. As result of investigations, The presence of the methylene group and bulky lateral groups in polymer chain have a great influence on the properties of polymers such as solubilities and thermal transitions. The optical textures of polymers revealed a weak birefringence in the melt and indicated that they form nematic mesophase. All polymers have very narrow mesophase temperature ranges.