Light waveguide feedthrough for optoelectronic modules and method for their manufacture

#The present invention relates to a light waveguide feedthrough for optoelectronic modules in which a light waveguide fiber is guided hermetically sealed through a metal tubule which is fastened in an opening in the module housing wall and a method for the manufacture of light waveguide feedthroughs.

#Electro-optical transducer modules for optical information technology must also have optical feedthroughs apart from electrical ones.

#In particular for reasons of cost no optical plug is to be used but rather the light waveguide fiber is to be guided directly through the housing wall, and especially in the form of a connecting fiber (pigtail). This feedthrough must be hermetically sealed and mechanically stable. Due to these stated requirements, the use of adhesion is eliminated.

#Features of the invention and additional objects of the invention will be more readily appreciated and better understood by reference to the following detailed description which should be considered in conjunction with the drawing.

#FIG. 1 illustrates a sectional view of a light waveguide feedthrough in accordance with the invention.

#FIG. 2 provides a sectional view of another light waveguide feedthrough according to the invention.

#The light waveguide feedthroughs depicted in FIGS. 1 and 2 include a light waveguide fiber 1 which is compression glazed into the housing-side front portion of a relatively thick-walled metal tubule 2 without external coating that is plain or bare and affixed by adhesion into its rear portion. To maintain the principle of the compression glass feedthrough, care must be taken in the selection of the material for the metal tubule, the fusing glass, and the fiber so that the metal tubule 2 is constructed of a material whose coefficient of thermal expansion is significantly higher than that of the fusing glass and of the material of the light waveguide fiber 1. Suitable material for metal tubule 2 are a nickel-iron or nickel-iron-cobalt-containing fusing alloy.

#The method of manufacture is the same for both implementations. The light waveguide fiber 1 (here in fixed-lead implementation) is placed in the glass solder capillary 8 (FIG. 1) or in the glass capillary 3 and the glass solder ring 4 (FIG. 2). The capillaries 3, 8 are previously placed into a suitable etching agent in order to eliminate all sharp edges which could damage the stripped light waveguide fiber 1 through slitting it slightly. Over the glass solder capillary 8 (FIG. 1) and the light waveguide fiber 1, or over the glass capillary 3, the glass solder ring 4, and the light waveguide fiber 1 (FIG. 2), the metal tubule 2 is placed. The upper portion of this, that is the housing-side front portion, is heated to the melting temperature of the glass solder and the lower portion, that is the rear portion, is cooled in order to protect the coating 5 of the light waveguide fiber 1 against burning. After the melt is solidified, it is under radial compression strain because the thermal expansion coefficient of the metal is greater than that of the glass solder. The inner cross section expansion 9, that is the widening of the metal tubule 2 on the inside in the illustrative embodiment depicted in FIG. 1, prevents tension ruptures at the transition glass solder capillarymelt. In the arrangement shown in FIG. 2, this is not necessary because the glass capillary 3 due to higher melting temperature is not fused on.

#In the illustrative embodiment shown in FIG. 3, the glazing cross section is restricted to a minimum and permits compressive glazing as well as also a fitted glazing. To this end, a metal tubule 7 of suitable material is hermetically tightly welded or soldered into the end of the housing-side front portion of the metal tubule 2 so that a cross sectional constriction is formed. Into this cross sectional constriction, the glass solder ring 4 is then glazed in. Further implementation then corresponds to that example described in particular in connection with FIG. 2. This implementation has the advantage that the material of the glass solder ring 4 is nearly independent of the material properties of the metal tubule 2 due to the additional metal tubule 7.