LIA-free Brillouin Optical Correlation Domain Analysis Enabled by Multi-core Fiber

We propose and demonstrate a Brillouin optical correlation-domain analysis sensor without lock-in-amplifier (LIA) based on the multi-core fiber (MCF). By utilizing the two symmetrical outer cores in a 7-core MCF, the Brillouin gain information along the fiber is extracted via the subtraction processing, thus circumventing the bottleneck of limited bandwidth of the LIA and the requirement of extra reference fiber links. An injection-locking configuration is employed to improve the measurement accuracy. The experimental results validate the high performance of the proposed BOCDA system with a spatial resolution of 10 cm and a strain measurement error of less than 15 μɛ over a measurement range of 37 m. Moreover, dynamic bending measurement and shape sensing are expected to be realized using rapid sweeping devices with the help of bending-dependent outer cores of the MCF.