Single-End-Access BOCDA Enabled by Multi-Core Fiber for Dynamic Strain Measurements

We propose and demonstrate a single-end-access dynamic Brillouin optical correlation-domain analysis sensor based on the multi-core fiber (MCF) and lock-in-amplifier-free detection scheme. The pump and the probe are individually injected into two cores at the same end of a 7-core MCF, where the cores are directly connected at the other end through fan-in/fan-out couplers to achieve single-ended access. Using another pair of cores as a reference path, the Brillouin gain information along two sensing cores is extracted through power subtraction processing, which eliminates the additional reference fiber links and further suppresses the parasitic intensity modulation noise. A measurement accuracy of 1.41 MHz is achieved at a 200-kHz sampling rate. Sensing information from two sensing cores are simultaneously acquired, allowing longitudinal and radial strain measurements. For proof of concept, measurements of up to 1-kHz longitudinal vibration and a 13.1-Hz radial bending-induced vibration are successfully demonstrated with 10-cm spatial resolution, showing great potential for fast high-resolution dynamic strain measurement.