In-line fiber étalon for strain measurement
Optics Letters Vol. 18, Issue 22, pp. 1973-1975 (1993) •doi: 10.1364/OL.18.001973

A description and demonstration of a fiber interferometer that uses a short segment of silica hollow-core fiber spliced between two sections of single-mode fiber to form a mechanically robust in-line cavity are presented. The hollow-core fiber is specifically manufactured to have an outer diameter that is equal to the outer diameter of the single-mode lead fibers, thereby combining the best qualities of existing intrinsic and extrinsic Fabry–Perot sensors. A dynamic strain resolution of ∼22n∊/Hz√ at frequencies of >5 Hz with a sensor gauge length of 137 μm is demonstrated.