All-fiber magnetic field sensor based on narrow-bandwidth laser internal cavity modulation with coated magnetic fluid

In this paper we present a magnetic probe structure based on magneto-fluidic and laser internal cavity modulation. We used a single-mode-no-core-single-mode fiber structure coated by a magnetic fluid as a sensing element, and inserted the sensing element in the inner cavity of a laser. Highly sensitive, high signal-to-noise ratio (SNR), narrow half-height width (FWHM) sensing signals have been obtained using intra-laser cavity modulation. The magnetic detection sensitivity of the sensor was improved, and a sensing system with a magnetic detection sensitivity of 1.76 × 10^-3 mw/Oe and a linearity of 99.709% was achieved. The temperature sensitivity is 0.035 μW/°C. The limit error of the magnetic field sensor is ±0.006035%. Meanwhile, output signal index of the sensing system is FWHM<40pm.