Multipoint acoustic impedance sensing based on frequency-division multiplexed forward stimulated Brillouin scattering

Acoustic impedance sensing based on forward stimulated Brillouin scattering (FSBS) in fiber has attracted the attention of researchers in recent years. Here, we propose a novel, to the best of our knowledge, multipoint sensing scheme based on FSBS, which explores frequency-division multiplexing. Since the resonance center frequencies of the FSBS-invoked acoustic modes are dependent on the fiber diameter, different fiber sections can be differentiated using carefully selected representative peaks in the FSBS spectrum. With a Sagnac loop structure, continuous-wave light is adopted for FSBS excitation, reducing the required fiber length for efficient opto-acoustic interaction. By evaluating the linewidths of representative peaks, simultaneous acoustic impedance sensing at multiple locations is realized with 0.8 m sensor size.