Method and apparatus for aligning fiber optic cables

#The present invention relates generally to apparatus for aligning the ends of optical fiber cables and more particularly to apparatus which permits the ends of the optical fiber cables to be displaced only along one co-ordinate axis and provides for increasing the sensitivity of detecting such relative displacement.

#Optical fibers are used extensively in displacement sensor technology. One method of obtaining a displacement measurement is to attach a first optical fiber cable to the object whose displacement is to be sensed while a second optical fiber cable, whose end is aligned with the end of the first optical fiber cable, is held stationary. One of the optical fiber cables has a light source attached to its other end while the other of the optical fiber cables has a light receiver attached to its other end. When the object is displaced, the light coupling between the two optical fiber cables changes, thus changing the amount of light received by the light receiver from the light source.

#An inherent problem associated with the foregoing optical fiber sensor apparatus is the alignment of the ends of the optical fiber cables relative to one another along the three co-ordinate axes. When measured displacement occurs along the X axis, sensitivity of the sensor depends on the relative position of the ends of the optical fiber cables along this axis. If the ends of the optical fiber cables are misaligned along this axis by more than the diameter of the cables, no signal is transmitted through the cables. The resulting sensitivity of the sensor also depends on misalignment of the ends of the optical fiber cables along the Y axis. In addition, the intensity of the light transmitted depends on the closeness of the ends of the optical fiber cables, i.e., the alignment of the cables along the Z axis.

#FIG. 1 is a perspective view of the present invention.

#FIG. 2 is a cross-sectional view of two optical fiber cables illustrating misalignment of the cables along the X and Y axes and also showing the common transmission area A between the two optical fiber cables.

#FIG. 3 is a cross-sectional view of two optical fiber cables each having a chord shaped portion of their ends blocked by a light absorbing/reflecting film and showing the common transmission area A therebetween.

#Referring now to the drawings where the illustrations are for the purpose of describing the preferred embodiment of the present invention and are not intended to limit the invention described herein, FIG. 1 is a perspective view of an apparatus 10 for aligning the ends of optical fiber cables 12 and 14 through the use of a beam member 16 which keeps the ends of the optical fiber cables 12 and 14 in a spaced apart relationship.

#The beam member 16 is of a dual cantilever beam construction having oppositely disposed web sections 18 and 20 interconnecting end sections 22 and 24. Aligned bores 26 and 28 are provided in end sections 22 and 24, respectively, of the beam member 16. End section 22 is attached to a fixed member 30 permitting end section 24 to be displaced along the X axis with respect thereto. Fixed member 30 has an aperture 32 therein aligned with bore 26 in end section 22. Optical fiber cable 12 is received through aperture 32 in fixed member 30 and is firmly encased within bore 26 so that its end 34 is positioned within the opening, shown generally by the numeral 36, between the web sections 18 and 20. Similarly, optical fiber cable 14 is received through and firmly encased within bore 28 in end section 24 so that its end 38 is positioned within the opening 36. Since the bores 26 and 28 are aligned along the Y axis, the ends 34 and 38 of the respective optical fiber cables 12 and 14 are similarly aligned. The distance between the ends 34 and 38 of the optical fiber cables 12 and 14 is maintained as small as possible. It has been found that a distance of between 0.001-0.002 inches provides best results.

#The opposite end 40 of optical fiber cable 12 is connected to a light source 42. Similarly, the opposite end 44 of the optical fiber cable 14 is connected to a light receiver 46.