Chirped fiber bragg grating cavity ring‐down for strain sensing using an OTDR

This work presents a fiber cavity ring down (CRD) configuration for the measurement of strain. An optical time‐domain reflectometer (OTDR) was used to send impulses down into the fiber loop cavity, inside of which a chirped fiber Bragg grating was placed to act as a strain sensing element. This technique could provide strain results with both conventional CRD‐based configuration and the OTDR. The CRD configuration provided a linear response to strain applied in the range 0–2000 με, and a sensitivity of 1.34 ns/με was obtained. For the same operation range, the OTDR interrogation allowed obtaining a periodic behavior due to fiber Bragg grating scanning of the wavelength peaks of the multimode laser source while increasing strain. It is shown that the OTDR interrogation method provide a ring‐down time response of about 8 μs which is a great improvement when compared to the conventional CRD configuration (23 μs). © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1442–1444, 2015