Fiber-grating sensors having longitudinal-strain-inducing jackets and sensor systems and structures including such sensors

摘要

A sensor comprising an optical fiber that includes a Bragg grating and a longitudinal-strain-inducing (LSI) jacket for inducing longitudinal strain into the optical fiber as a function of a transverse load, i.e., pressure or force. As the LSI jacket induces strain into the optical fiber, the fiber grating deforms, thereby changing the character of light reflected from the grating. The changes in character of the reflected light can be measured using suitable optical instrumentation. Additional physical characteristics that can be measured/sensed using an LSI-jacket-based sensor include moisture content/presence, chemical content/presence, and temperature. A transverse-load-sensing sensor can include transverse-load-applying structures that compress the LSI jacket under transverse load, causing the jacket to controllably elongate and thereby induce longitudinal strain into the optical fiber. Chemical and moisture LSI jackets can comprise materials that swell in the presence of the chemical or moisture.

主权项

1. A sensor assembly for measuring a compressive load applied externally to the sensor assembly, the sensor assembly comprising:
a first coated optical fiber; first and second rigid transverse-load-applying structures having corresponding respective first and second confronting faces facing one another and spaced from one another so as to define a gap, said first confronting face having a length and including a first elongate recess extending the entirety of said length, said first elongate recess containing said first coated optical fiber along the entirety of said length and configured so that said first coated optical fiber has at least one discrete line of contact with said first elongate recess along the entirety of said length; and a bonding material securing said first and second rigid transverse-load-applying structures to one another with said first coated optical fiber in contact with each of said first and second rigid transverse-load-applying structures; wherein said first coated optical fiber comprises:
a first optical fiber having a first Bragg grating applied thereto and located between said first and second rigid transverse-load-applying structures; anda first longitudinal-strain-inducing jacket coating coupled to said first optical fiber and extending along the entirety of said length, said first longitudinal-strain-inducing jacket coating having a uniform thickness along the entirety of said length and selected and configured to induce increasing uniform axial tensile strain in said first optical fiber at said first Bragg grating as a function of increasing magnitude of the compressive load when the compressive load is applied across the sensor assembly in a direction perpendicular to each of said first and second confronting faces of said first and second rigid transverse-load-applying structures.