Highly sensitive fiber-optic sensor for low-frequency magnetic field detection based on injection locking of OEO

A fiber-optic sensing system integrating a Fabry-Perot interferometer (FPI) with an injection-locked optoelectronic oscillator (IL-OEO) is proposed for highly sensitive low-frequency magnetic field detection. The cavity length change of the FPI caused by the magnetostrictive probe is directly coupled into the OEO loop. Through injection locking, a precise mapping from magnetic field-induced frequency shifts to phase variations is realized, and the phase noise of OEO at near-carrier is greatly suppressed, enabling low-noise phase demodulation in the low-frequency range. A phase sensitivity of 21.4 mrad/μT and a magnetic field resolution of 0.97 nT/Hz^1/2 at 100 Hz are achieved, and the relationship between sensitivity and injection ratio is also experimentally investigated. The proposed system offers a promising solution for high-performance low-frequency magnetic field sensing.