| 摘要 |
The invention relates to an optical waveguide, whose sheath consists of organic material (e.g. silicone) and whose core consists of inorganic material (e.g. quartz). Since the refractive index of the sheath nM rises faster than that of the core nK in the case of cooling of the optical waveguide, both refractive indices are equal at a limiting temperature Tg. By reducing the difference in the refractive indices, the attenuation of the optical waveguide is increased. Since, therefore, there exists a defined connection between attenuation and temperature, such an optical waveguide can be applied as a low temperature thermometer or as a temperature-controlled attenuation element (switch, modulator). If only a small region of the optical waveguide is cooled and the emerging light is collected, a reversible exit coupling element results. The optical waveguide need not be mechanically manipulated in any of the applications (Fig. 1). <IMAGE>
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