Investigation and Optimization of Photoelectric Detection Circuit With a Differential Structure Suited to Borehole Optically Pumped Magnetometer

The common-mode interference (CMI) caused by the high-temperature environment and the integration of multiple sensors affects the magnetic measurement accuracy of the magnetometer, and the noise performance of the photoelectric detection circuit (PDC) is also a key factor affecting the sensitivity of the magnetometer. In order to suppress CMI and improve the sensitivity of magnetic measurement, a differential structure PDC is proposed, and the equivalent noise model is established by analyzing the circuit noise source. By optimizing the parameters, the PDC with low-noise performance and low CMI is designed and applied to the optically pumped magnetometer to realize magnetic measurement. The test results show that the differential structure PDC can effectively suppress the CMI, the signal-to-noise ratio (SNR) can be increased by 1.4 times compared with the single-ended PDC, and the voltage noise is 57.65 nV/Hz1/2, which is consistent with the theoretical analysis results of the noise model and meets the expected requirements of low-noise design of the PDC of low-noise magnetometer. Finally, the self-made PDC is employed in the borehole optically pumped magnetometer for magnetic field measurement, which verifies the effectiveness of the circuit.