‘High-sensitivity fiber-optic microvolt voltage sensor based on a piezoelectric stack transducer and an active phase-shifted grating’

Electroencephalographic (EEG) signals are weak electrical signals generated by the synchronous activity of brain neurons. They can be recorded by devices and serve as the core basis for studying brain functions, diagnosing neurological diseases and realizing brain-computer interaction. Non-invasive fiber optic sensors face significant challenges in EEG measurement due to their low sensitivity. To address this issue, this study proposes an active phase-shifted (APS) grating sensor for EEG signal monitoring. The APS grating fiber Bragg grating is bonded to a piezoelectric stack transducer to enable EEG signal conversion, and the phase generated carrier-differential cross multiplication demodulation technology is adopted to process interference light intensity signals. For external noise interference, the study further introduces a reference optical fiber and combines it with the reference optical bridge technology. By leveraging the noise correlation between the reference and sensing channels, the system achieves noise separation and elimination. Experimental results show that the sensitivity of this EEG signal acquisition sensor reaches 1.332 × 10 −3 rad μV −1 ; the system successfully collects and reconstructs EEG signals across multiple frequency bands, with a minimum detectable signal of 5 μV. This confirms the sensor’s capability for non-invasive, real-time EEG signal collection.