Hermetic waveguide seals and method of making them

#Not Applicable

#The present invention relates to hermetic waveguide seals and a method of making hermetic waveguide seals.

#Optical fibers are used in a wide variety of applications ranging from telecommunications to medical technology and optical components.

#Exemplary embodiments of the invention will now be described in conjunction with the following drawings wherein like numerals represent like elements, and wherein:

#FIG. 1 is a schematic cross-sectional view of a fiber ferrule assembly of the present invention prior to the application of heat;

#FIG. 2 is a schematic cross-sectional view of a fiber feedthrough assembly of the present invention prior to the application of heat;

#The present invention provides a hermetic fiber-optic seal and a method of making such hermetic seal. Advantageously, the hermetic fiber-optic seal in accordance with the present invention provides a hermetic fiber ferrule or feedthrough having a good reliability. The hermetic fiber-optic seal and the process in accordance with the instant invention for making a hermetic fiber-optic seal is described below. The optical fiber is hermetically sealed in a ferrule using a glass soldering process for two main applications. The first application is a hermetic fiber ferrule wherein the optical fiber is end-stripped and packaged in a ferrule. The fiber end (terminus) is then polished in accordance with predetermined specifications. The second main application for hermetic fiber-optic seals is a hermetic fiber feedthrough wherein the optical fiber is window-stripped and sealed in a ferrule. Furthermore, in accordance with another embodiment of the invention, the hermetic fiber-optic seal of the present invention provides a hermetic fiber ribbon feedthrough and a method of making the same using a glass soldering process.

#Reference is now being made to FIG. 1 showing a schematic cross-sectional view of a fiber ferrule assembly 100 of the present invention prior to the application of heat. A glass solder pre-form 110 is custom designed to meet predetermined specifications using commercially available solder glass materials, such as lead borate glasses, for example, having a matrix of ceramic fillers. Other materials can be chosen according to desired specifications. As seen in FIG. 1, the glass solder pre-form 110 is stacked inside an outer sleeve 120, such as a metal, metallic alloy, ceramic, or glass ferrule, between a first glass sleeve 130 and a second glass sleeve 140, wherein the bores of the first and the second glass sleeve and the bore of the glass solder pre-form are aligned. In accordance with an embodiment of the present invention, the first and the second glass sleeve 130 and 140 are borosilicate glass sleeves having a melting point of approximately 1200° C. Alternatively, other glass materials having a substantially higher melting point than the solder glass material are chosen, for example quartz having a melting point of about 1600° C. The glass sleeves 130 and 140 and the pre-form 110 have a relatively large inner diameter in comparison to the diameter of a fiber 150 which is centered within the bores through glass sleeves 130 and 140 and the glass solder pre-form 110.

#As seen in FIG. 1, fiber 150 has an end-stripped portion 152 which protrudes a short distance beyond an end face 132 of the first sleeve 130. The first and the second glass sleeve 130 and 140 protrude outside the outer sleeve 120. The outer sleeve 120 is heated, for example by means of an inductive heater element 160 surrounding the outer sleeve, to a temperature (ca. 450° C.) at which the glass solder melts. However, the material for the first and the second glass sleeve 130 and 140 is chosen such that their melting point is higher than the melting point of the pre-form 110 so that the glass sleeves 130 and 140 maintain their solid shape during the extrusion process.