Abstract: One or more optical fiber gratings are used to sense environmental effects that can vary the spacing between the lines of the grating to vary the center frequency of the spectral envelope, either reflected or passed thereby. Light of the sensor grating's spectral envelope is transmitted to a local optical filter unaffected by the environmental effect and compared with the spectral envelope of the local optical filter to produce an intensity modulated signal, which is detected to sense the environmental effect. The sensor systems so constructed may have one or more local optical filters and those local optical filters may be modulated to reduce the effects of noise, broaden the dynamic range, vary the sensitivity or discriminate in a multiplexed embodiment. The system can be operated either open or closed loop. In addition, the fiber grating may have multiple gratings at the same location so that different kinds of effects or effects from different directions can be sensed from a single location.

Abstract: One or more optical fiber gratings are used to sense environmental effects that can vary the spacing between the lines of the grating to vary the center frequency of the spectral envelope, either reflected or passed thereby. Light of the sensor grating's spectral envelope is transmitted to a local grating unaffected by the environmental effect and compared with the spectral envelope of the local grating to produce an intensity modulated signal, which is detected to sense the environmental effect. The sensor systems so constructed may have one or more local gratings and those local gratings may be modulated to reduce the effects of noise, broaden the dynamic range, vary the sensitivity or discriminate in a multiplexed embodiment. The system can be operated either open or closed loop.

Abstract: There is provided by this disclosure a method and apparatus for making fiber optic couplers that is comprised generally of the steps of stretching a fused optical fiber pair at a predetermined rate to produce first a tapered section, second a constant diameter cylindrical section, and third a final tapered section. The two optical fibers are placed in juxtaposition under a predetermined load, heated to a predetermined temperature until they fuse together to form a single entity having a predetermined width, length and circular cross section. The two moveable platforms apply a predetermined tensile load to the fibers and move the fibers past a heat source in a controlled manner to form the different sections.

Abstract: A fiber optic coupler is provided having first and second optical fibers fused together along a predetermined length having fused tapered ends for the input and output of optical energy and a constant diameter section therebetween to facilitate coupling of optical energy between the first and second optical fibers. The constant diameter section provides a higher efficient coupling action and a stronger, more rugged coupler.