Method and apparatus for determining the shape of a flexible body

A multimode/single-mode fiber interface for a flexible body, comprising:

• Bragg grating sensor means coupled to the body and linearly displaced at preselected intervals along a length of the body, responsive to bending axial deformation, torsion and temperature, and adapted to output signals indicative thereof,
• an optical slip ring coupling said Bragg grating sensor means to one or more optical fibers;
• means for detecting fractures in said optical fibers;
• means for protecting said Bragg grating sensor means;
• a light source for inputting light into each of said Bragg grating sensor means;
• and
• multiplexing signal processing means connected to said Bragg grating sensor means and adapted to provide a real-time display of the shape of the body.

A method of determining, the shape of a flexible body, comprising, the steps of:

• (a) measuring thermomechanical strains about the x—x neutral axis, the y—y neutral axis, the z—z neutral axis, and the x-y axis of the shape, the thermomechanical strain measurements being taken at a multiplicity of fiber optic measurement nodes, each of which include one or more Bragg grating sensors displaced at preselected intervals about and along the body;
• (b) measuring temperature at said multiplicity of fiber optic measurement nodes;
• (c) decoupling x—x, y—y, z—z, and x-y mechanical strains, respectively, from corresponding ones of said thermomechanical strains measured at said multilicity of fiber optic measurement nodes;
• (d) fitting said x—x mechanical strains to an x-curve fitting function, said y—y mechanical strains to a y-curve fitting function, said z—z mechanical strains to a z-curve fitting function, and said x-y mechanical strains to a torsional fitting function;
• and
• (e) determining x, y, z, and torsional deformations of the body, respectively, through an x-curve processing function, a y-curve processing function, a z-curve processing function, and a torsional-curve processing function.

A monitoring method for maintaining the shape of a towed flexible body, comprising the steps of:

• (a) coupling a plurality of fiber optic measurement nodes to the body, each of which includes one or more Bragg grating sensor means and is linearly displaced at preselected intervals therealong;
• (b) adapting each said fiber optic measurement node to be responsive to environmental factors selected from the group consisting of bending, axial deformation, torsion, and external temperature of the body;
• (c) inputting light into each of said fiber optic measurement nodes from a light source selected to generate output signals from said Bragg grating sensor means measurement nodes that are indicative of said environmental factors;
• (d) multiplexing said output signals;
• (e) decoupling said multiplexed signals with strain-to-shape structural analysis means;
• and
• (f) first displaying the shape of the body in real-time by inputing said decoupled multiplexed signals to display means;
• (g) providing a post-processing means for adjusting a monitored shape of the body based on said display, and
• (h) adiusting the body.