US RE31579 E
A fiber optic reed switch is disclosed. A pair of fiber optic cables are mounted to the ends of cantilever reed arms by means of supports providing coaxial alignment of the cables upon closure of the reed arms to complete an optical circuit.
Fiber optic switches are known wherein a shutter is driven between the facing ends of a pair of fiber optic cables to break the light path therebetween. A disadvantage of these switches is that the width of the shutter physically limits the narrowness of the gap between the facing cable ends whereby a certain amount of transmission loss between the cables cannot be avoided due to the diverging cone of emitted light. Additionally, because of the shutter, the gap is not hermetically sealed, thus giving rise to further transmission losses due to optical contamination of the cable end faces.
The present invention relates to a fiber optic switch constructed to eliminate the necessity of a shutter.
An object of the invention is to provide a fiber optic switch of the aforementioned character having a narrower gap between facing fiber optic cable ends to minimize transmission losses therebetween.
Another object is to provide a fiber optic switch of the aforementioned character which is amendable to hermetic sealing of the gap to prevent contamination of the facing cable ends.
Another object of the invention is to provide a simple, low cost fiber optic switch having a minimum number of parts, versatile and numerous applications, and which is susceptible of numerous variations.
Another object of the invention is to provide conversion means for adapting a variety of existing electrical switch structures to optical switching applications.
Other objects and advantages will hereinafter appear.
FIG. 1 shows a fiber optic reed switch as the preferred embodiment of a shutterless fiber optic switch constructed in accordance with the invention.
FIG. 2 shows a "double throw" type switch as an alternate embodiment of FIG. 1.
There is shown in FIG. 1 a reed switch comprising an elongated hermetically sealed glass envelope 2 having a pair of magnetically permeable reed arms 4 and 6 extending through and sealingly mounted to the distal ends of the envelope. The reed arms extend into the envelope in cantilever form and overlap at their inner ends 4a and 6a which provide stops for attraction of the reed arms under the influence of a magnetic field. In the absence of a magnetic field, the reed arms return to their normal separated position due to their inherent bias.
Sealingly extending through the distal ends of the envelope are also a pair of fiber optic cables 8 and 10. Support members 12 and 14 mount the ends of cables 8 and 10 to the inner ends 4a and 6a of the reed arms such that the fiber optic cables are aligned upon closure of the reed arms whereby to complete an optical circuit.
Support member 12 is attached to the top of reed arm 4 at end 4a. Support member 14 is attached to the top of reed arm 6 and spaced slightly from end 6a to allow clearance of end 4a upon closure. Each of the support members has a bore 12a, 14a, extending therethrough for rigidly securing a respective fiber optic cable end disposed therein. The support members are constructed such that the height of bore 14a above the top surface of reed arm end 6a is equal to the height of bore 12a above the top surface of reed arm end 4a plus the vertical thickness of reed arm end 4a.
The disclosed embodiment thus eliminates the need for a shutter, hence enabling a narrower gap 16 between the facing fiber optic cable ends, whereby to reduce transmission losses therebetween.
FIG. 2 shows an alternate embodiment wherein a third fiber optic cable 18 sealingly extends into the envelope and has an inner end rigidly secured in support member 20 which is attached to the envelope wall. In the normal separated position of reed arms 4 and 6, support member 12 abuts the envelope wall acting as a stop, and cables 8 and 18 are aligned to thus complete an optical circuit therealong.
Among other possible modifications are the inclusion of bimetal strips along the underside of reed arms 4 and 6 within the envelope to provide movement thereof in response to temperature, and hence a temperature to light switch.
The concepts and teachings herein are of course applicable to other areas in the switch art within the scope of the appended claims.