Abstract

A strain sensor has a first optical fiber (212) including first (212e1) and second (212e2) ends and also includes lead-in (12) and lead-out (16) optical fibers. One (12) of the lead-in and the lead-out fiber has a first end (12e) affixed to the first end of the first fiber, forming a first partially reflective surface (214). The other one (16) of the lead-in and lead-out fibers has a first end (16e) located at a second distance (S) from the second end (212e2) of the first fiber (212). The sensor includes a glass tube (30), with a bore (32), affixed to at least the other one of the fibers, and holds the first end of the other one of the fibers to define coaxial partial reflectors (14, 18) at the second end (212e2) of the first fiber and the first end (16e) of the other one of the fibers. In one embodiment, the one of the fibers is the lead-in fiber. In one embodiment, the bore (32) diameter of the glass tube (30) is large enough to accommodate the first, lead-in, and lead-out fibers, the first fiber is located within the bore, and the first ends of the lead-in and lead-out fibers are also within the bore, but portions of the lead-in and lead-out fibers remote from their first ends are without the bore of the tube (30). In this particular embodiment, the tube is affixed at its ends (34, 36) to the lead-in and lead-out fibers, so at least the first fiber (212) is free for axial motion within the bore of the tube.