A warm-white light-emitting diode (LED) without blending of different kinds of phosphors is demonstrated. An approach that consists of a blue LED chip and a wavelength-conversion phosphor is carried out. The phosphor is a newly developed yellowish orange CaEuSiAlON ceramic phosphor with high efficiency. The CIE1931 chromaticity coordinates (x, y) are (0.458, 0.414), the color temperature is 2750 K, and the luminous efficacy of this LED is 25.9 lm/W at room temperature and with a forward-bias current of 20 mA. The chromaticity of the assembled LED is more thermally stable than that of a LED with a conventional oxide phosphor (YAG:Ce) because of the better thermal stability of the oxynitride phosphor.
In this paper, a simultaneous strain and temperature measurement method using a polarization maintaining and absorption reducing (PANDA) fiber is applied to a distributed sensing system based on optical frequency domain reflectometry (OFDR). A fiber Bragg grating (FBG) whose length is 100 mm is inscribed into a PANDA fiber to form a long-length PANDA-FBG. We demonstrated simultaneous measurements of strain and temperature distributions experimentally. In experiments the long-length PANDA-FBG was bonded on a steel plate and various strains and temperatures were applied at the same time to the plate. Consequently strain and temperature were successfully discriminated. However, larger errors were observed for distributed measurement results.
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