Repeatable sensitivity of optical-time-domain-reflectometry-based strain measurement

摘要

Optical time-domain reflectometry (OTDR) is a simple and rugged technique for measuring quantities such as strain that affect the propagation of light in an optical fiber. For engineering applications of OTDR, it is important to know the repeatable limits of its performance. The authors constructed an OTDR-based, submillimeter resolution, strain measurement system from off-the-shelf components. The system repeatably resolves changes in time of flight to within (plus minus)2 ps. Using a 1-m, single-mode fiber as a gauge and observing the time of flight between Fresnel reflections, we observed a repeatable sensitivity of 400 microstrains. Using the same fiber to connect the legs of a 3-dB directional coupler to form a loop, we observed a repeatable sensitivity of 200 microstrains. Realizable changes to the system that should improve the repeatable sensitivity to 20 microstrains or less are discussed.