Structural monitoring system using fiber optics

A method of determining the locations of physical movement occurring along a continuum of points between spaced points on a structure, said method including the steps of:

• (a) attaching with attachment means at least one optical fiber continuously to said structure to extend from at least one of the spaced points to the other and thereby engage all points along the structure between said spaced points so that physical movement of the structure between said spaced points will result in physical movement of said optical fiber;
• (b) passing a first light signal into said optical fiber;
• and
• (c) continuously detecting individual multiple light reflections in said fiber along the continuum of points between spaced points to identify points along the structure at which a physical movement has taken place and to provide an indication of the magnitude of all such movements.

An apparatus for monitoring a physical movement between spaced points on a structure including, in combination:

• (a) at least one optical fiber;
• (b) attachment means between said optical fiber and said structure for attaching said optical fiber continuously to said structure to extend from at least one of the spaced points to the other and thereby directly engage all points along the structure between said spaced points so that physical movement of the structure between said spaced points will result in physical movement of the optical fiber;
• (c) means for passing a first light signal into said optical fiber;
• (d) means for detecting and indicating reflection changes in said first light signal as a consequence of said physical movement;
• and,
• (e) means responsive to said reflection changes for indicating the location and magnitude of said physical movement.

An apparatus for monitoring a physical movement between spaced points on a structure including, in combination:

• (a) at least on optical fiber;
• (b) means for attaching said optical fiber continuously to said structure to extend from at least one of the spaced points to the other and thereby engage all points along the structure between said spaced points;
• (c) means for passing a first light signal into said optical fiber;
• (d) means for detecting and indicating reflection changes in said first light signal as a consequence of said physical movement;
• (e) means responsive to said reflection changes for indicating the location and magnitude of said physical movement;
• (f) at least one additional optical fiber secured to said structure along portions of the structure spaced from said one optical fiber;
• (g) means for passing a second light signal into said additional optical fiber;
• (h) means for detecting changes in said second light signal resulting from said physical movement of the structure;
• and
• (j) means for comparing the changes in said first light signal with the changes in said second light signal to thereby enable the direction of said physical movement to be determined.

An apparatus for monitoring a physical movement between spaced points on a structure including, in combination:

• (a) at least one optical fiber;
• (b) attachment means between said optical fiber and said structure for attaching said optical fiber continuously to said structure to extend from at least one of the spaced points to the other and thereby engage all points along the structure between said spaced points so that physical movement of said structure between said spaced points will result in physical movement of said optical fiber;
• (c) means for passing a first light signal into said optical fiber;
• (d) means for detecting and indicating reflection changes in said first light signal as a consequence of said physical movement;
• and
• (e) means responsive to said reflection changes for indicating the location and magnitude of said physical movement;
• (f) said optical fiber including a core and surrounding cladding, said cladding having an index of refraction different from the index of refraction of said core, said first light signal passing through said core being substantially retained in the core by internal reflections from the interface of said core and cladding so long as the index of refraction of said cladding is not changes;
• a sheath surrounding said cladding, said sheath having a coating of fixed particulate material uniformly spread over its interior wall surface in intimate engagement with the outer surface of said cladding, said particulate material having a diameter of from 5 to 23 microns, said particulate material radially moving into and distorting the homogeneity of at least a portion of said cladding whenever said sheath, cladding and core are subject to tension as a result of said physical movement of said structure attached to said fiber, the distortion resulting in a change in the index of refraction of the cladding such that some light is permitted to escape from said core and cladding at the location of said physical movement thereby generating Rayleigh back scattering reflection changes in said light signal.

A method of monitoring a physical movement occurring at any point between spaced points on a structure including the steps of:

• (a) attaching at least one optical fiber continuously to said structure to extend from at least one of the spaced points to the other and thereby engage all points along the structure between said spaced points;
• (b) passing a first light signal into said optical fiber;
• (c) detecting reflection changes in said first light signal resulting from said physical movement to thereby provide an indication that a physical movement has taken place and an indication of the location and magnitude of said movement;
• (d) attaching at least one additional optical fiber to said structure extending along portions of the structure spaced from said one optical fiber;
• (e) passing a second light signal into said additional optical fiber;
• (f) detecting changes in said second light signal resulting from said physical movement of the structure;
• and
• (g) comparing the changes in said first light signal with the changes in said second light signal to thereby enable the direction of said physical movement to be determined.