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Abstract

The invention provides an apparatus, and method of making the apparatus, for optical sensing of parameters in high temperature environments, such as chemical reaction zones, combustion zones, high temperature drying processes, and the like. Moreover, the optical apparatus of the invention are able to operate in high temperature environments without need for associated cooling equipment. The optical elements of the sensors are fabricated from a material that is refractory, is transparent to electromagnetic radiation, has low thermal conductivity, and that reduces in viscosity when heated to a temperature well above the operating temperature to which it will be subjected in the monitoring environment. Preferably, the optical elements, and even mechanical elements, are made of a vitreous silica material. This allows attachment of optical and mechanical elements to each other through a 'direct adhesion' process whereby heat is applied in the region of adjacent surfaces of these elements causing reduction in viscosity of the vitreous silica, flowing and thereafter hardening to form permanent connections. Since vitreous silica has a low thermal conductivity, the locally applied heat does not substantially affect the optical properties of optical elements that are so treated for attachment.

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First Claim