Abstract: A Michelson interference optical fiber temperature sensor for detecting fringe contrast change is provided. It includes a light source, an optical fiber coupler connected to a first optical fiber and a second optical fiber, a coarse wavelength division multiplexer, a first photodetector, a second photodetector, a display device, and a processing circuit connected to the display device. The light source, optical fiber coupler and coarse wavelength division multiplexer are connected sequentially in that order. The coarse wavelength division multiplexer is connected to the first photodetector and the second photodetector individually. The first photodetector and the second photodetector are connected to the processing circuit. An end of the first optical fiber or the second optical fiber facing away from the optical fiber coupler is connected to a semiconductor. It has advantages of simple and fast manufacturing process, safe and reliable sensor, stable signal, low cost, high sensitivity and high precision.

Abstract: The present disclosure relates to a high-pitched loudspeaker, which widens the starting frequency of the high-pitched loudspeaker, and the high-pitched loudspeaker has a smoother intermediate frequency curve and less distortion. A high-pitched loudspeaker comprises a magnetic circuit system, a voice coil, and a diaphragm connected to the voice coil, wherein a first cavity is formed between the magnetic circuit system and the voice coil and the diaphragm, the high-pitched loudspeaker further comprises a back cover, the magnetic circuit system is arranged between the diaphragm and the back cover, and a second cavity is formed between the back cover and the magnetic circuit system, a through-hole is opened on the magnetic circuit system which communicates the first cavity and the second cavity to constitute an air gap cavity of the high-pitched loudspeaker.