Strain based optical fiber devices

Abstract

Optical fiber devices include optical fibers having grating portions with in-fiber gratings having optical characteristics which are changed by the use of strain inducing members. The strain inducing members are connected to optical fibers in such a way that the strain applied to an in-fiber grating in an optical fiber is greater than the strain in the strain inducing members. Basically, a given percentage change in a dimension of one of the strain inducing members causes a greater percentage change in a dimension of the grating portion. The strain inducing members may apply lengthwise or radial strain to the grating portion. Arrangements with mechanical coupling of two fibers using one or more strain inducing members are useful for producing equal strain in grating portions of two fibers for interferometer configurations or other applications. The strain inducing members can be acoustic wave transducers, piezoelectric transducers, pneumatic actuators, hydraulic actuators, members inducing strain due to heat induced dimension change, members inducing strain due to cooling induced dimension change, and motor controlled dimension changing structures. An arrangement using two different types of these strain inducing members provides for different response time delays for implementing changes in strain and provides reduced steady state power consumption. A feedback circuit using a strain gauge provides the ability to adjust and maintain strain (and corresponding optical characteristics) of an in-fiber grating at a desired value.